The role of various transporters in the placental uptake of ofloxacin in an in vitro model of human villous trophoblasts

Introduction

Six years after the US Food and Drug Administration approval of the broad-spectrum antibiotic ofloxacin (OFLX), the chiral switching of this racemic mixture resulted in a drug composed of the L-optical isomer levofloxacin (LVFX). Since both fluoroquinolones (FQs) were introduced to the pharmaceutical market, they have been widely prescribed by physicians, with careful administration during pregnancy and breastfeeding. Therefore, the role of the influx and efflux placental transporters in the concentrations of these drugs that permeate through human placental barrier model was investigated in this study.

Methods

The contribution of major carriers on the transplacental flux of OFLX and LVFX uptake into choriocarcinoma BeWo cells was evaluated in the presence vs absence of well-known inhibitors.

Results

Our results reveal that neither the influx transporters such as organic cation transporters, organic anion transporters, and monocarboxylate transporters nor the efflux transporters such as P-glycoprotein or breast cancer resistance protein significantly affected the transport of OFLX. In contrast, multiple transporters revealed pronounced involvement in the transfer of the levorotatory enantiomer in and out of the in vitro placental barrier. These data suggest a non-carrier-mediated mechanism of transport of the racemic mixture, while LVFX is subjected to major influx and efflux passage through the placental brush border membranes.

Conclusion

This study provides underlying insights to elucidate the governing factors that influence the flux of these FQs through organ barriers, in view of the controversial safety profile of these drugs in pregnant population.

Cannabidiol changes P-gp and BCRP expression in trophoblast cell lines

Objectives. Marijuana is the most commonly used illicit drug during pregnancy. Due to high lipophilicity, cannabinoids can easily penetrate physiological barriers like the human placenta and jeopardize the developing fetus. We evaluated the impact of cannabidiol (CBD), a major non-psychoactive cannabinoid, on P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) expression, and P-gp function in a placental model, BeWo and Jar choriocarcinoma cell lines (using P-gp induced MCF7 cells (MCF7/P-gp) for comparison). Study design. Following the establishment of the basal expression of these transporters in the membrane fraction of all three cell lines, P-gp and BCRP protein and mRNA levels were determined following chronic (24-72 h) exposure to CBD, by Western Blot and qPCR. CBD impact on P-gp efflux function was examined by uptake of specific P-gp fluorescent substrates (calcein-AM, DiOC2(3) and rhodamine123(rh123)). Cyclosporine A (CsA) served as a positive control. Results. Chronic exposure to CBD resulted in significant changes in the protein and mRNA levels of both transporters. While P-gp was down-regulated, BCRP levels were up-regulated in the choriocarcinoma cell lines. CBD had a remarkably different influence on P-gp and BCRP expression in MCF7/P-gp cells, demonstrating that these are cell type specific effects. P-gp dependent efflux (of calcein, DiOC2(3) and rh123) was inhibited upon short-term exposure to CBD. Conclusions. Our study shows that CBD might alter P-gp and BCRP expression in the human placenta, and inhibit P-gp efflux function. We conclude that marijuana use during pregnancy may reduce placental protective functions and change its morphological and physiological characteristics.

Oral versus rectal ibuprofen in healthy volunteers

OBJECTIVE

Ibuprofen is a safe and effective non steroidal anti-inflammatory drug (NSAID). Ibuprofen suppositories are marketed in Europe; but data regarding pharmacokinetics of rectal vs. oral ibuprofen in humans is scarce. The objective of this study is to compare the pharmacokinetics of single-dose rectal vs. oral ibuprofen in healthy adult volunteers.

METHODS

Ten healthy adult male volunteers, aged 20-37 years, received in a non-blind, cross-over setting, two formulations of ibuprofen. First, a 400 mg (about 5 mg/kg) of racemic ibuprofen suppository; second (after a three week washout period) the same dosage of ibuprofen syrup. Blood samples were collected before dosing and for 12 hours after administration. Pharmacokinetics analysis was preformed.

RESULTS

Mean peak plasma concentration (Cmax) of rectal ibuprofen was considerably lower, and the mean time to peak (Tmax) considerably longer, compared to oral ibuprofen. Absorption of rectal ibuprofen was considerably lower than oral ibuprofen, with a relative bioequivalence of 63%. Rectal ibuprofen reached therapeutic plasma concentration (>10 µg/ml) 45 minutes after dosing and remained in that range for four hours. The values of Vd/F and CL/F also differ significantly after rectal and oral administration, while no difference was found in the elimination rate constant (Kel) or half-life elimination (t1/2).

CONCLUSIONS

Racemic ibuprofen suppository has lower bioavailability compared with ibuprofen syrup. Therapeutic plasma concentrations of ibuprofen were reached 45 minutes after dosing and remained in that range for 4 hours. Ibuprofen suppositories can contribute to the management of fever and pain when the oral route is not available.

Nitrofurantoin transport by placental choriocarcinoma JAr cells: involvement of BCRP, OATP2B1 and other MDR transporters

OBJECTIVE

To determine the role of BCRP in nitrofurantoin (NF) transport in JAr cells and the possible contribution of OATP2B1, P-gp and MRPs to this transport.

METHODS

Cells were incubated with various BCRP, P-gp, MRPs, organic anion transporting polypeptide (OAT) and OATP2B1 inhibitors for 15 min, followed by incubation for 30 min with NF, with or without the inhibitors mentioned earlier. NF cytotoxicity was examined using neutral red (NR) assay. Intracellular NF levels were analyzed by HPLC.

RESULTS

NR assay showed that incubation conditions with NF (as carried out in our experiments) were not cytotoxic. Incubation with specific inhibitors of BCRP (FTC, Chrysin and Novobiocin), showed a significant increase in NF accumulation in the cells. Inhibitors of OATP2B1 (EGCG and BSP) had no influence on NF accumulation. Specific inhibitors of P-gp and MRPs (Verapamil and Indomethacin, respectively) also had no influence on NF accumulation in JAr cells.

CONCLUSIONS

NF is probably a specific substrate of BCRP, and BCRP has a major active role in NF transport in JAr cells. For the first time, we showed, that P-gp, MRPs, and the OATP2B1, probably have a negligible contribution to NF transport in JAr cells.

Progesterone levels in cesarean and normal delivered term placentas

BACKGROUND

One of the most important hormones synthesized by the placenta during pregnancy is progesterone. The regulating mechanisms of progesterone synthesis and the mechanism responsible for the spontaneous onset of labor in women are still not fully understood. Progesterone is thought to have been involved in human parturition. The objective of this study was to compare the levels of progesterone in the human placentas, at the end of the gestation (37-41 weeks) in vaginal versus cesarean deliveries, and to evaluate the pattern of progesterone accumulation, instantly following its synthesis by the human placenta at the end of the pregnancy.

METHODS

Progesterone levels in human placental tissue were determined by immunochemiluminescent analysis, following tissue homogenization. Progesterone secretion and accumulation pattern in the placental tissue was demonstrated using the ex vivo, closed, dual perfusion system of isolated human placental cotyledon.

RESULTS

Immunochemiluminescent analysis of progesterone levels in human normal and cesarean-delivered placentas showed that placentas following normal vaginal delivery store higher concentrations of progesterone, and produce progesterone more intensively. Results obtained from 120-min perfusions (of vaginal and cesarean-delivered placentas) showed that progesterone tended to accumulate in the maternal rather than the fetal compartment.

CONCLUSIONS

These data indicate that progesterone levels continuously rise till the end of pregnancy, with no apparent drop in progesterone levels during the labor process. In addition, progesterone is released from the syncytiotrophoblast preferably into the maternal component of the placental tissue.

Transfer of ciprofloxacin, ofloxacin and levofloxacin across the perfused human placenta in vitro

OBJECTIVE

To investigate the transfer of therapeutically important fluoroquinolones: ciprofloxacin, ofloxacin and levofloxacin, through the isolated perfused human placenta, from the maternal to the fetal compartment.

STUDY DESIGN

Isolated placental cotyledons from normal human term placentae were dually perfused with M199 medium enriched with 3g/l bovine serum albumin and 1g/l glucose. Perfusion rates were 12 and 6 ml/min in the maternal and fetal circulation, respectively. Maternal and fetal closed circulation was used to evaluate steady-state concentrations and transplacental gradient formation. Eighteen placentae were used in our study: six for each experiment with ciprofloxacin, ofloxacin and levofloxacin were added to the maternal circulation. Samples were collected from the maternal and fetal compartments. Antipyrine was used as a reference drug that crosses the placenta by simple diffusion. The concentrations of ciprofloxacin, ofloxacin, levofloxacin and antipyrine were measured by specific HPLC (high performance liquid chromatography) methods. Results are presented as mean+/-S.D.

RESULTS

In all the placentae, ciprofloxacin, ofloxacin, levofloxacin crossed the placenta from the maternal to the fetal compartment. The mean transplacental transfer percent of ciprofloxacin was 3.2+/-0.7% and the transplacental transfer index, the ratio of transplacental transfer between ciprofloxacin and antipyrine was 0.34+/-0.12. The mean transplacental transfer percent of ofloxacin was 3.7+/-2.4% and the transplacental transfer index was 0.33+/-0.3. The mean transplacental transfer percent of levofloxacin was 3.9+/-1.5% and the transplacental transfer index was 0.34+/-0.2.

CONCLUSIONS

Only a small fraction of ciprofloxacin, ofloxacin and levofloxacin passed from the maternal to the fetal compartment. This fraction is significantly smaller compared to antipyrine. This may indicate that there is a barrier to the transport of fluoroquinolones in human placenta.

Metabolic activation of zebularine, a novel DNA methylation inhibitor, in human bladder carcinoma cells

Zebularine (2(1H)-pyrimidinone riboside, Zeb), a synthetic analogue of cytidine that is a potent inhibitor of cytidine deaminase, has been recently identified as a general inhibitor of DNA methylation. This inhibition of DNA methyltransferase (DNMT) is hypothesized to be mechanism-based and result from formation of a covalent complex between the enzyme and zebularine-substituted DNA. Metabolic activation of Zeb thus requires that it be phosphorylated and incorporated into DNA. We have quantitatively assessed the phosphorylation and DNA incorporation of Zeb in T24 cells using 2-[(14)C]-Zeb in conjunction with gradient anion-exchange HPLC and selected enzymatic and spectroscopic analyses. The corresponding 5'-mono-, di- and triphosphates of Zeb were readily formed in a dose- and time-dependent manner. Two additional Zeb-containing metabolites were tentatively identified as diphosphocholine (Zeb-DP-Chol) and diphosphoethanolamine adducts. Intracellular concentrations of Zeb-TP and Zeb-DP-Chol were similar and greatly exceeded those of other metabolites. DNA incorporation occurred but was surpassed by that of RNA by at least seven-fold. Equivalent levels and similar intracellular metabolic patterns were also observed in the Molt-4 (human T-lymphoblasts) and MC38 (murine colon carcinoma) cell lines. For male BALB/c nu/nu mice implanted s.c. with the EJ6 variant of T24 bladder carcinoma and treated i.p. with 500mg/kg 2-[(14)C]-Zeb, the in vivo phosphorylation pattern of Zeb in tumor tissue examined 24h after drug administration was similar to that observed in vitro. The complex metabolism of Zeb and its limited DNA incorporation suggest that these are the reasons why it is less potent than either 5-azacytidine or 5-aza-2'-deoxycytidine and requires higher doses for equivalent inhibition of DNMT.

Lack of interaction of digoxin and P-glycoprotein inhibitors, quinidine and verapamil in human placenta in vitro

OBJECTIVE

To determine the effect of quinidine and verapamil, known antiarrhythmic agents and P-glycoprotein (Pgp) inhibitors, on digoxin transport from the maternal to the fetal compartment in the isolated perfused human placenta.

STUDY DESIGN

Isolated placental cotyledons from normal human placentae (n=20) were dually perfused with M199 medium enriched with albumin (0.3%) and glucose (0.1%). The maternal and the fetal circulation flow rates were 12 and 6 ml/min, respectively. Closed circulations were used to evaluate steady state transplacental gradient formation. In six placentae quinindine was added to the maternal circuit; after 45 min of perfusion, digoxin was added to the maternal circulation. The effect of verapamil on digoxin transfer from the maternal to the fetal compartments was explored in five placentae. In six additional placentae the transfer of digoxin was studied in the absence of quinidine. Transplacental passage of digoxin was calculated from repeated fetal and maternal perfusate samples. Digoxin levels were determined in perfusate samples by fluorescence polarization immunoassay. Antipyrine was added to the maternal reservoir of all placentae as reference substance.

RESULTS

The transfer of digoxin (alone) and in the presence of quinidine or verapamil was 10.93+/-3.71, 9.00+/-5.2 and 12.94+/-4.86%, respectively. The levels of digoxin in the fetal compartment, 0.62+/-0.20, 0.48+/-0.29 and 0.60+/-0.26 ng/ml, respectively, were not significantly affected by quinidine and verapamil. These Pgp modulators, also did not influence significantly the steady state levels of digoxin in the maternal compartment.

CONCLUSION

Neither quinidine nor verapamil affected the transplacental transfer of digoxin in vitro in normal human placentae. In contrast to the other tissues, they do not inhibit Pgp activity in term human placentae.

Pharmacokinetics and organ distribution of N-methanocarbathymidine, a novel thymidine analog, in mice bearing tumors transduced with the herpes simplex thymidine kinase gene

PURPOSE

The conformationally rigid nucleoside, N-methanocarbathymidine [(N)-MCT] exerts a potent antiproliferative effect both in vitro and in vivo against murine colon cancer cells (MC38) expressing the herpes simplex virus thymidine kinase gene (MC38/HSV-tk). Metabolic studies have revealed that high levels of (N)-MCT triphosphate accumulate in transduced cells and are incorporated into DNA, resulting in cell death. The objective of the present study was to assess the pharmacokinetic profile of (N)-MCT in C57BL/6 mice bearing nontransduced MC38 and MC38/HSV-tk tumors.

METHODS

Male black C57BL/6 mice bearing subcutaneous tumors derived from wildtype and HSV-tk-transduced MC38 murine colon cancer cells in the left and right flank, respectively, were treated i.p. with radiolabeled (N)-MCT (100 mg/kg). Mice were killed at each of the predetermined times after drug administration. Blood, urine, tumors and various organs and tissues were obtained for measurement of drug levels.

RESULTS

Plasma and tissue concentrations of (N)-MCT peaked at 0.25-0.5 h. The major pharmacokinetic parameters calculated for (N)-MCT in plasma were: T(1/2)beta 4.7 h, AUC 147 micro g.h/ml, CL 0.69 l/kg per h. The penetration of (N)-MCT into brain and testes was slow. Between 4 and 24 h after drug administration, the levels of (N)-MCT measured in HSV-tk-expressing tumors were significantly higher than in wildtype tumors. HPLC analysis of methanolic extracts of plasma and urine obtained at various times after drug administration revealed no (N)-MCT metabolites in the plasma, and the compound was secreted unchanged in the urine.

CONCLUSIONS

After i.p. injection into mice, (N)-MCT was rapidly absorbed and distributed in all organs examined. No drug metabolites were detectable in plasma and the compound was secreted unchanged in urine. These results are essential for the future development and in postulating the most efficient use of (N)-MCT in the HSV-tk enzyme prodrug system for gene therapy approaches for the treatment of cancer.

Antitumor activity and metabolic activation of N-methanocarbathymidine, a novel thymidine analogue with a pseudosugar rigidly fixed in the northern conformation, in murine colon cancer cells expressing herpes simplex thymidine kinase

N-Methanocarbathymidine [(N)-MCT], a thymidine analogue incorporating a pseudosugar with a fixed Northern conformation, exhibits antiherpetic activity against both herpes simplex virus (HSV) HSV-1 and HSV-2, with a potency greater than that of the reference standard, ganciclovir (GCV). In the present study, we have assessed the cytotoxic activity in vitro of (N)-MCT in wild-type murine colon cancer cells (MC38) and in cells expressing the herpes simplex thymidine kinase gene (MC38/HSV-tk), and the antitumor activity of (N)-MCT in vivo against HSV-tk transduced and nontransduced MC38 murine tumors. In vitro, when assessed over a 48-h period, the growth-inhibitory activity (IC50) of (N)-MCT toward MC38/HSV-tk cells was 2.9 microM. In parallel studies, the cytostatic activity of the reference compound GCV in these tumor lines was 3.0 microM. In studies in vivo, both (N)-MCT and GCV (100 mg/kg) given twice daily for 7 days completely inhibited the growth of HSV-tk-transduced MC38 tumors while exhibiting no effect on nontransduced MC38 tumors in mice. In nontransduced cells both in vitro and in vivo, only low levels of (N)-MCT and its monophosphate could be detected after administration of the parent drug, whereas in HSV-tk-transduced cells (N)-MCT was phosphorylated to its respective mono-, di-, and triphosphates. Furthermore, data showed that (N)-MCT incorporated in high levels into cellular DNA whereas trace levels were measured into RNA. These observations indicate that (N)-MCT may be a useful candidate prodrug for HSV-tk suicide gene therapy of cancer.

Albumin-dependent digoxin transfer in isolated perfused human placenta

OBJECTIVE

To determine the effects of albumin (BSA) concentration in perfusion medium on digoxin transfer in isolated perfused human placental cotyledon.

STUDY DESIGN

Isolated placental cotyledons from 13 normal human placentas were dually perfused after cannulating artery and vein of the chorionic plate and piercing 4 catheters through the corresponding basal plate with M199 medium enriched with BSA and glucose. Flow rates were 12 and 6 ml/min in the maternal and fetal circuits, respectively. Digoxin was added to the maternal reservoir at a final concentration of 5.51 +/- 1.00 ng/ml. BSA in maternal and fetal perfusate was kept at 3 concentrations: 1, 3 and 5 mg/ml (Groups I, II, III). Transplacental passage of digoxin was calculated from repeated fetal and maternal perfusate samples collected over 3 hours in the 3 groups. Digoxin levels were measured by FPIA (TDx, Abbott).

RESULTS

There was no transfer of digoxin from the maternal to fetal compartment when the concentration of BSA was 1 mg/ml. Increasing the concentration of BSA led to a substantial increase in the transfer of digoxin to the fetal compartment. Steady state levels of digoxin in the fetal compartment were 0.61 +/- 0.19 ng/ml at 3 mg/ml of BSA.

CONCLUSION

Maternal and fetal serum concentration of BSA affect digoxin transfer in isolated perfused human placentas. Three mg/ml are considered to be the optimal albumin concentration.

Thiopurine methyltransferase activity in the Jewish population of Israel

OBJECTIVE

6-Mercaptopurine is used therapeutically for its immunosuppressant and cytotoxic properties. It is deactivated by thiopurine methyltransferase (TPMT), which shows genetic polymorphism in many populations. In North American populations, TMPT activity exhibits a trimodal activity pattern. In Oriental populations, TPMT shows almost a unimodal pattern of activity. The purpose of the present study was to assess the activity of TPMT in a Jewish male population sample in Israel.

METHODS

The study was approved by the Israeli Ministry of Health. Blood samples of 2.5 ml were collected in heparinized tubes from 134 males. The red blood cell (RBC) fraction of each individual was washed and hemolyzed. TPMT activity in the RBC hemolysate was determined using a radioactive assay with tritiated S-adenosyl methionine as a methyl donor.

RESULTS

The activity of TPMT ranged from 3.2 nmol/h/ml to 42.9 nmol/h/ml packed RBCs with mean and median activities of 18.6 nmol/h/ml and 17.9 nmol/h/ml packed RBCs, respectively. The distribution frequency of TPMT was very close to the unimodal by analysis of normal distribution.

CONCLUSION

The pattern of distribution of TPMT in the Jewish population of Israel is closer to that of East Asian populations than European and North American populations. This observation may have relevance for the usage of 6-mercaptopurine and azathioprine as therapeutic agents in the Jewish population.

Drug metabolizing enzymes in the ostrich (Struthio camelus): comparison with the chicken and the rat

The activities of selected hepatic and renal drug-metabolizing enzymes of the ostrich, chicken and rats were compared. The concentration of glutathione in the liver and kidneys of the avian species was significantly lower than in the rat. The activity of ostrich hepatic glutathione S-transferase was 2-fold higher than that of the chicken and the rat and the renal glutathione S-transferase of the ostrich was 10 times higher than that of the rat. The activity of ostrich hepatic UDP-glucuronyl transferase was significantly lower than that of the rat. The activities of hepatic cytochrome P450 1A and 2B1/2 as measured by the dealkylation of ethoxy- and methoxyresorufin, respectively, were higher int he avian species than the rat; no difference was noticed in the activity of aniline hydroxylase. The results show that the activity of ostrich drug-metabolizing enzyme system is quantitatively different from the rat and in many cases also from the chicken.

Red blood cell permeability to thiol compounds following oxidative stress

The permeability of red blood cells (RBCs) to thiol containing compounds, reduced glutathione (GSH) and N-acetyl cysteine (NAC), has been studied in control adult and neonatal cells and after oxidative stress. NAC penetrates the cell membrane easily while GSH hardly permeates. We measured their capacity to enhance intracellular non-protein thiols (NPSH), after inducing damage to the membrane by formation of defects. Diamide, phenazine methosulfate (PMS) and t-butyl hydroperoxide (BHP) were chosen as exogenous oxidants, each inducing damage by a different mechanism. Our data indicate that although neonatal cells are more sensitive to oxidative stress, only membrane damage induced by diamide, renders adult and neonatal cells permeable to GSH. NAC treatment enhances thiol levels in cells exposed to oxidizing agents, as well as in control cells.

The bioavailability of febantel in dehydrated camels

In the present study the bioavailability of febantel paste and febantel suspension was investigated in the fully hydrated and the dehydrated camel. The serum concentrations of febantel and its metabolites, fenbendazole, oxfendazole and fenbendazole sulfone were determined by high performance liquid chromatography following extraction with ether. The exposure to febantel and its metabolites in fully hydrated camels was significantly higher in camels dosed with febantel paste compared to febantel suspension, as measured by AUC and Cmax. The AUC and Cmax of fenbendazole and oxfendazole were significantly lower in dehydrated camels as compared to control camels dosed with febantel paste. The systemic availability of febantel suspension in control and dehydrated camels was very low and differences between dehydration and control phases were insignificant. The low systemic availability of febantel in camels dosed with febantel suspension may cause nematodes to become resistant to this anthelmintic. It is, thus, suggested to increase the dose of febantel paste in dehydrated camels in order to increase the exposure to febantel and its metabolites. The binding of febantel, fenbendazole, oxfendazole and fenbendazole sulfone to camels' serum proteins was over 85%. Oxfendazole was only about 70% bound. Dehydration of 10 days did not affect the binding of these benzimidazole derivatives to serum proteins.

Lidocaine elimination and monoethylglycinexylidide formation in the dehydrated camel

The elimination kinetics and the formation of the monoethylglycinexylidide (MEGX), a major metabolite of lidocaine, were studied in camels deprived of water for 14 days. The study was conducted on four camels in a crossover design. Lidocaine was administered intravenously at a dose of 1 mg/kg to adult female camels when water was given ad libitum (stage 1) and to the same camels after 14 days of dehydration. Blood samples were taken up to 6 h after dosing. Serum lidocaine and MEGX levels were analysed by polarization fluorescence immunoassay. The elimination profiles of lidocaine and the formation of the metabolite MEGX in the two phases of the study were essentially identical. No difference in any pharmacokinetic parameter was noticed between normally hydrated and water-deprived camels. It is thus concluded that dehydration does not affect the cytochrome P450 isozymes involved in degradation of lidocaine to MEGX nor does it affect the hepatic blood flow, which is a major determinant in the clearance of lidocaine. The very low clearance of lidocaine in the camel in comparison with other ruminant or monogastric mammals may be associated with the camel's ability to survive drought in the desert.

Disposition kinetics of tylosin tartrate administered intravenously and intramuscularly to normal and water-deprived camels

The disposition kinetics of tylosin tartrate administered intravenously (i.v.) at 10 mg/kg and intramuscularly (i.m.) at 20 mg/kg were studied in normal camels and in the same camels at the end of a 14 day water-deprivation period. After i.v. treatment, serum tylosin concentrations in the water-deprived camels were significantly higher, rate of drug elimination was slower, the volume of distribution was significantly smaller, and total body clearance was significantly slower than in the normal camels. On the other hand, serum drug concentrations were lower in the water deprived camels after i.m. dosing, the mean absorption time was significantly shorter and the i.m. availability was significantly smaller than in the normal camels. Water-deprivation was thought to cause reduced rate of tylosin elimination by the liver, as was shown for antipyrine--a drug which is eliminated from the body exclusively by the liver. Redistribution of tylosin in tissues concomitant with a greater proportion of drug in blood and extracellular fluid of water-deprived camels was suggested as a partial explanation for the higher serum drug levels seen after i.v. dosing. The low i.m. availability observed in the water-deprived camels implies that i.v. is the route of choice for tylosin administration to ill, dehydrated camels.

Antipyrine disposition in the dehydrated camel

In the present study the effects of water deprivation in the camel (Camelus dromedarius) on the pharmacokinetic profile of antipyrine were assessed. A cross-over design was used. The pharmacokinetics of antipyrine in adult and young camels were compared. Antipyrine was administered intravenously to young and adult female camels when water was available ad libitum and to the adult camels after 14 days of dehydration. The elimination half-life of antipyrine in watered adult camels was 136.5 +/- 16.7 min. The half-life of elimination and the mean residence time of antipyrine were significantly prolonged following dehydration. The observed effects of water deprivation were not a function of age, as the pharmacokinetic profile of antipyrine in young camels was similar to that of the adults, but more likely due to the changes in oxidative metabolic capacity of the liver as a result of a reduced general metabolism. The results of the present study also show that the intrinsic clearance of antipyrine is proportional to the camel's body weight, as previously shown for other mammalian species.

Loperamide effects on hepatobiliary function, intestinal transit and analgesia in mice

Loperamide effects on hepatobiliary function, analgesia and gut transit were studied in mice. Varying doses of the antidiarrheal drug, loperamide, were administered to mice by intracerebroventricular, intravenous, subcutaneous and intragastric routes. Gut motility was determined by intestinal transit of India ink, analgesia by warm water tail flick latency, and hepatobiliary function by retention of the anionic dye, sulfobromophthalein in plasma and liver. When given by all routes at modest doses, loperamide slowed intestinal transit. Analgesia, a centrally mediated opiate effect, was only detected after intracerebroventricular or subcutaneous loperamide at high, near-toxic doses. Elevations of plasma and liver sulfobromophthalein were noted at routes and doses which slowed gut transit, well below those needed for analgesia. Intragastric loperamide at one fortieth its LD50 caused marked elevation of sulfobromophthalein levels and gut slowing, but no analgesia. Sulfobromophthalein elevation and gut slowing by intragastric loperamide were not affected by spinal cord transection but were reversed by naltrexone, an opiate antagonist. Non-toxic doses of loperamide slow gut transit and modify hepatobiliary function in mice by opiate actions at peripheral sites.

Effects of clonidine and IBMX on sulfobromophthalein disposition in rats

Clonidine, an alpha 2-adrenoceptor agonist, inhibited the biliary excretion, reduced the plasma clearance and increased the hepatic retention of sulfobromophthalein (BSP) in a dose related fashion in rats. The maximal effects of clonidine on BSP disposition occurred about 4 h after pretreatment. The effects of clonidine on biliary excretion and hepatic retention of BSP were retained following laparotomy (with or without bile duct cannulation); however, the effect of clonidine on plasma disappearance profile was not retained following abdominal surgery. Isobutylmethylxanthine (IBMX) affected BSP disposition in a similar fashion as clonidine, in rats without bile duct cannulation only; no effect of IBMX could be observed in bile duct cannulation rats. Yohimbine, an alpha 2-adrenoceptor antagonist, reversed the effects of clonidine, but not of IBMX, on BSP disposition. It thus seems that clonidine and IBMX exert their effects on BSP disposition by different mechanisms and probably at different sites.

Bromosulfophthalein disposition in chronically bile duct obstructed rats

The disposition of bromosulfophthalein was studied in chronically bile duct obstructed rats. In this model a catheter was inserted into the common bile duct and the distal tip was sealed. Resumption of bile flow was achieved with great ease. Obstruction of bile duct for 18 days in rats resulted in elevated bilirubin, ALT, AST, and alkaline phosphatase levels. Portal hypertension developed within this period (11.6 +/- 0.5 in obstructed rats vs. 8.6 +/- 0.6 mm Hg in sham-operated group). After the bile duct obstruction was opened, the half-life time for elimination of bromosulfophthalein (42.30 +/- 6.47 min) was longer than in sham-operated rats (21.23 +/- 3.34 min). Plasma clearance was reduced by 70% in bile duct obstructed rats. In spite of increased bile flow rate, biliary excretion of the dye was reduced by 40% in chronically bile duct obstructed rats. Hepatic glutathione levels were significantly reduced by 20% in this model. The specific activity of glutathione S-transferase with chlorodinitrobenzene and styrene oxide, as substrates, was reduced by 50% and 30%, respectively. However, the percent of conjugated bromosulfophthalein in bile was similar to that of sham-operated rats.

Disposition of hexobarbitone and antipyrine in DOCA-hypertensive rats

The disposition of antipyrine and hexobarbitone, and their effects on drug metabolizing hepatic enzymes have been investigated in DOCA-hypertensive rats. Antipyrine pharmacokinetic parameters were the same in hypertensive and control animals. Hexobarbitone sleeping time was longer in hypertensive rats compared with controls, while the activity of hepatic hexobarbitone hydroxylase was the same in both groups. Hepatic aminopyrine-N-demethylase activity was elevated in hypertensive rats while aniline hydroxylase and aryl hydrocarbon hydroxylase were lower. Glucuronyl transferase was the same in both groups. The sensitivity of the central nervous system of hypertensive rats to hexobarbitone was not altered, as determined by hexobarbitone concentration in blood and in brain. The total hepatic blood flow (arterial and portal) was significantly increased. Thus it is suggested that the difference in the disposition of the two drugs is probably not due to drug metabolizing enzyme activity. It is likely that the increase in total hepatic blood flow and rapid saturation of hepatic hexobarbitone metabolizing enzymes have significant roles in the slower metabolism and increased activity of hexobarbitone in hypertensive rats as compared with control rats.

Hepatobiliary effects of morphine are mediated in the brain

Morphine slows hepatobiliary elimination of sulfobromophthalein in rodents, raising dye levels in plasma and liver. Earlier studies showed these effects to be independent of other opiate effects such as bile duct spasm, hypothermia or blood gas changes resulting from respiratory depression. Because opiate receptors are distributed throughout the body, within the central nervous system and at peripheral sites including the gastrointestinal tract, experiments were performed to ascertain whether central or peripheral sites mediate the hepatobiliary effects of morphine. Sulfobromophthalein was administered intravenously to mice and its levels were measured in plasma and liver. Tail-flick latency indicated centrally mediated analgesia. Inhibited intestinal transit of India ink reflected an opiate effect with a significant peripheral component. When injected into a cerebral ventricle morphine was much more potent in producing analgesia and raising sulfobromophthalein levels than when administered intravenously or intraperitoneally. An intravenous dose of naloxone that reversed morphine analgesia also prevented sulfobromophthalein elevation but did not prevent gut slowing. Naltrexone injected in a cerebral ventricle also reversed analgesia and sulfobromophthalein elevation but not intestinal slowing. The polar opiate agonist N-methylmorphine did not cause analgesia or raise sulfobromophthalein levels at peripheral intraperitoneal doses to 100 mg/kg. When given in a central ventricle at 4 x 10(-3) mg/kg, this agent produced analgesia and raised sulfobromophthalein but did not slow intestinal transit. After spinal cord transection, intravenous morphine did not retard the tail-flick response or affect sulfobromophthalein disposition, but peripherally mediated intestinal transit was slowed as it was in intact mice. These experiments demonstrate parallel opiate effects on analgesia and on BSP disposition but not on intestinal transit.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaminophen hepatotoxicity: is there a role for prostaglandin synthesis?

The hepatotoxicity of acetaminophen (APAP) overdose depends on metabolic activation to a toxic reactive metabolite via hepatic mixed function oxidase. In vitro studies have indicated that APAP may also be cooxidized by prostaglandin H synthetase. The present experiments were designed to assess the possible contribution of hepatic prostaglandin synthesis to APAP toxicity. Adult fed male mice were overdosed with 400 mg APAP/kg. Liver toxicity was estimated by measurement of serum transaminases. Hypertonic xylitol or sodium chloride (2250 mOsm/l), administered intragastrically to stimulate prostaglandin synthesis, increased APAP toxicity. By contrast, the cyclooxygenase inhibiting drugs aspirin (at 25 mg/kg) and indomethacin (at 10 mg/kg) protected against APAP-induced toxicity. APAP kinetics were not affected by hypertonic xylitol or indomethacin, nor were hepatic glutathione levels in overdosed mice. Imidazole, a nonspecific thromboxane synthetase inhibitor, also protected overdosed mice. This drug prolonged hexobarbital sleeping time and prevented the depletion of hepatic glutathione that followed APAP intoxication. Thus, the data support the conclusion that APAP-induced hepatoxicity may be modulated not only by inhibition of cytochrome P450 mediated oxidation, but also by controlling hepatic cyclooxygenase activity.

Interaction of clonidine and morphine with lidocaine in mice and rats

Morphine and clonidine both elevated plasma levels of lidocaine to the same extent in mice while slowing lidocaine metabolism to deethylated products. The effects of clonidine on lidocaine disposition were reversed by yohimbine. Mice given morphine, 20 mg/kg sc, or clonidine, 0.2 mg/kg sc, had similar, 30-50%, elevation of plasma lidocaine levels at 15 min after lidocaine, 15 mg/kg iv, when compared to saline-treated animals. Despite similarity of effect on plasma lidocaine, mice treated with morphine were much more susceptible to lethal effects of lidocaine than were mice given clonidine. At iv doses of 22 mg/kg or higher, lidocaine caused death in nearly all morphine-treated mice, while even 32 mg/kg lidocaine caused only 11% mortality after saline or clonidine. Clonidine, 0.5 mg/kg sc, and morphine, 20 mg/kg sc, both raised plasma lidocaine levels in rats, but only morphine depressed respiration, causing hypoxia, hypercapnia, and acidosis and increasing lidocaine lethality. These data suggest that potentiation of lidocaine toxicity by morphine is due primarily to changes in blood gases rather than to elevation in lidocaine levels.

Liver function and protein binding in camels

1. Dehydration of camels for 10 days resulted in reduction of liver functions, expressed in longer half life and reduced clearance of bromosulfophthalein (BSP), elevated AST (ALT levels were below the limit of detection of the method) and reduced serum albumin concentrations. 2. Binding of BSP to camel serum proteins by gel permeation chromatography and by equilibrium dialysis showed very strong binding. 3. Binding parameters of various drugs to camels serum by equilibrium dialysis showed close similarities both qualitatively and quantitatively to those of humans. 4. Albumin seems to be the major serum binding protein of BSP.

Morphine effects on gentamicin disposition and toxicity in mice

Morphine has been shown to reduce renal and hepatic clearance of several xenobiotics in rodents. After iv administration of gentamicin, 10 to 30 mg/kg, its plasma levels were elevated in mice given morphine, 20 mg/kg sc. Plasma clearance of gentamicin was nearly halved by morphine, due primarily to lowering of the elimination constant of gentamicin from 0.03 to 0.02 min-1 (p less than 0.01). Morphine also significantly reduced urine levels of gentamicin and urine volume. In mice given naloxone, 2 mg/kg sc, morphine did not significantly raise plasma levels of gentamicin nor reduce its elimination into urine. Mice were made tolerant by morphine administration for 9 days at ascending doses to 100 mg/kg twice daily. An acute challenge with morphine, 20 mg/kg, was less effective in raising plasma levels of gentamicin or lowering its urinary elimination in tolerant mice than after chronic saline treatment. Partial tolerance to acutely administered morphine and reversal of morphine effects by naloxone suggest opioid receptor-mediated reduction of glomerular filtration by morphine in mice. Despite marked elevation of plasma gentamicin levels in morphine-treated mice, narcotic administration did not significantly increase the acute toxicity of a single dose of gentamicin. LD50 of acutely administered iv gentamicin was 51.6 mg/kg after saline and 45.3 mg/kg after treatment with morphine, 20 mg/kg sc. However, this dose of morphine enhanced the lethality of intravenously infused gentamicin. Morphine administration significantly reduced the dose of infused gentamicin needed to achieve the critical lethal plasma level.

Clonidine effects on disposition of xenobiotics in rats: inhibited elimination of flow-limited but not extraction-limited agents

1. The alpha 2-adrenoceptor agonist, clonidine, reduces the hepatobiliary clearance of the anionic dye, sulphobromophthalein (BSP) in rodents. We now compare the effects of clonidine on BSP elimination with its effects on disposition of compounds which are metabolized by hepatic microsomal mixed function oxidases. 2. BSP, 100 mg kg-1 was administered i.v. to rats at 4 h after s.c. saline or clonidine, 0.2 mg kg-1. Thirty min later, plasma BSP levels were 121.4 +/- 2.25 micrograms ml-1 in saline-treated rats, while in clonidine-treated rats they were 631.5 +/- 141.0 micrograms ml-1. Clonidine raised hepatic BSP levels from 256.0 +/- 28.9 micrograms g-1 tissue to 568.5 +/- 86.5 micrograms g-1. 3. Acute administration of clonidine (0.2 mg kg-1 s.c.) or repeated clonidine dosing (0.2 mg kg-1, s.c. twice daily for 10 days) did not affect the disposition of intravenously administered [14C]-antipyrine (15 mg kg-1). 4. Activities of the P450 mixed function oxidase enzymes, aniline hydroxylase and aminopyrine N-demethylase, were identical in liver microsomes from saline-treated rats and in microsomes from rats given single or multiple s.c. doses of clonidine (0.2 mg kg-1). 5. Addition of clonidine or other 2-substituted imidazoles at concentrations up to 2 microM did not affect the activities of aniline hydroxylase or of aminopyrine N-demethylase in suspensions of rat liver microsomes. Other substituted imidazoles, including cimetidine, clotrimazole and metronidazole, at concentrations of 0.2 microM or higher, inhibited the activities of these microsomal enzymes. 6. Clonidine slowed BSP elimination, which is probably hepatic blood flow-limited, but not the extraction-limited elimination of antipyrine, which is metabolized by hepatic microsomal enzymes.

Monitoring theophylline therapy using citric acid-stimulated saliva in infants and children with asthma

Saliva stimulation is required for measurement of drugs in saliva. Chewing on a piece of paraffin, which is the method usually used for saliva stimulation, requires cooperation of the patient and, thus, is inapplicable in infants and young children. To assess the value of determining theophylline concentrations from noninvasively obtained saliva in this age group, we studied the theophylline plasma to saliva concentration ratio in citric acid-stimulated saliva. Theophylline concentration was measured in 137 simultaneously obtained paired specimens of plasma and saliva from 68 patients 2 1/2 months to 14 years of age treated with theophylline for asthma (dosage 20.8 +/- 5.2 mg/kg/d, mean +/- SD). Saliva secretion was stimulated by placing citric acid crystals on the tongue. A strong and highly significant correlation was observed between both determinations (r = .96; P less than .01). The plasma to saliva ratio was 1.78 +/- 0.22 (mean +/- SD), with theophylline concentrations between 3.1 and 32.1 micrograms/mL of plasma. The ratio of estimated to actual plasma theophylline concentrations was 1.02 +/- 0.12 (mean +/- SD). Interindividual coefficient of variation of plasma to saliva theophylline concentrations ratios was 12.4%; mean intraindividual coefficient of variation was 5.3%. The use of citric acid for saliva stimulation is easily applicable to infants and young children. Compared with blood drawing, stimulation of saliva secretion by citric acid is painless and noninvasive, is more readily accepted to patients, is at least as clinically relevant for theophylline determination, and allows frequent measurements of drug levels for individualization of the dosage with samples taken at home.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiulcer activity of clonidine: lack of effect on gastric prostaglandins

Clonidine and paraaminoclonidine prevented the formation of indomethacin-induced gastric ulcers in female rats. This protective activity was blocked by coadministration of yohimbine. Therefore, the antiulcer activity of clonidine was due to its peripheral alpha-2 agonistic action. Because indomethacin is a prostaglandin synthetase inhibitor, its ulcerogenic effect has been attributed to a state of prostaglandin (PG) deficiency. We therefore investigated the possibility that the protective effect of alpha-2 adrenoceptor agonists could be mediated by stimulation of the biosynthesis of PGs in the stomach. However, the results failed to show increased production of PGE2 or 6-keto-PGF1, either in stomach slices in vitro or in the gastric mucosa of rats pretreated with clonidine, whether indomethacin was used or not. It is concluded that the activity of clonidine in preventing indomethacin-induced gastric erosions in rats is probably not related to prostaglandins.

Effects of adrenoceptor agonists and antagonists on sulfobromophthalein disposition in mice

The effects of alpha 2-adrenoceptor agonists on sulfobromophthalein (BSP) disposition in mice were studied. It was found that agents with both central and peripheral activities (clonidine, guanabenz, B-HT 920 and methyldopa) as well as peripherally acting alpha 2-adrenoceptor agonists (para amino-clonidine and St 91) inhibited sulfobromophthalein disposition in the mouse, and also caused substantial hypothermia. The effects of these agonists were inhibited by yohimbine, a specific alpha 2-antagonist, except for those of para amino-clonidine where only partial reversal was achieved. The effects of clonidine on BSP disposition were also reversed by piperoxan but not by the alpha 1-adrenoceptor antagonists, prazosin and phenoxybenzamine, nor by the beta-blocker, propranolol. These results suggest that, in mice, peripheral alpha 2-adrenoceptors are involved in the effects of the alpha-agonists on BSP disposition.

Tolerance to effects of clonidine and morphine on sulfobromophthalein disposition in mice

Chronic treatment of mice with clonidine or morphine caused tolerance to the analgesic and thermoregulatory effects of these drugs. After chronic morphine, mice also became tolerant to the analgesic and thermoregulatory effects of clonidine. Cross tolerance to the hypothermic effect of morphine was demonstrated after chronic clonidine administration, but no diminution of morphine-induced analgesia could be shown. Morphine and clonidine acutely increased the retention of sulfobromophthalein (BSP) in plasma and liver. Chronic dosing with morphine or clonidine caused partial tolerance and cross-tolerance to the rise in hepatic BSP caused by an acute challenge with either agonist. However, both drugs elevated plasma BSP levels similarly in tolerant and non-tolerant mice. Thus, regimens which readily induced tolerance to the analgesic and hypothermic effects of morphine or clonidine were only partially effective in modifying the acute hepatobiliary effects of these drugs.

The effects of estrus cycle on drug metabolism in the rat

The effect of the female rat estral cycle on microsomal drug metabolism in-vivo and in-vitro has been studied. Two microsomal enzymes, aminopyrine-N-demethylase and aniline hydroxylase showed a greater specific activity (p less than 0.01) in the diestrus phase of the estral cycle while the oxidative enzyme aryl hydrocarbon hydroxylase and the conjugative enzyme, glucuronyl transferase, were not affected. In vivo studies which included theophylline and antipyrine metabolism, and hexobarbital sleeping times showed no difference between the different phases of the estral cycle. Conflicting evidence about the effect of steroid sex hormones on hepatic drug metabolism is discussed.

Changes in theophylline metabolism during postnatal development in rat liver slices

The metabolism of theophylline was studied in liver slices of young and adult rats. Theophylline and six metabolite fractions were recognized in adult liver by thin-layer radiochromatography and high performance liquid chromatography: 1-methyluric acid; 1-methylxanthine; 1,3-dimethyluric acid and/or 3-methylxanthine; caffeine; a uracil derivative and two unknown polar compounds. Preincubation with caffeine or theobromine inhibited theophylline metabolism. Allopurinol decreased the formation of three metabolite fractions but markedly increased the production of 1-methylxanthine. SKF 525-A inhibited the overall metabolism of theophylline. The specific activity of the enzyme system was 3.2 +/- 0.4 nmoles X (g liver)-1 X hr-1 in the 4- to 5-day-old rat and increased to a peak of 25.7 +/- 1.7 in the 28-day-old; values for Km and Vmax in the 7- and 28-day-olds were 132.1 and 67.5 microM, and 23.9 and 52.1 nmoles X (g liver)-1 X hr-1 respectively. Theophylline and the same six metabolites were identified in young and adult rats, but the development pattern was not uniform. Peak age-related activity and involvement of mixed-function oxidase system are features which are common to theophylline and caffeine metabolism. Xanthine oxidase played a role in theophylline metabolism. Formation of caffeine from theophylline was not dependent on a lack of activity of other pathways.

Theophylline pharmacokinetics in pregnant and lactating rats

As a preliminary investigation to a human study, we examined the pharmacokinetics of theophylline in pregnant and lactating rats. Three groups of female rats--pregnant, lactating, and virgin controls were injected IP with theophylline solution. Pregnant rats eliminated theophylline at a slower rate than both lactating rats and virgin controls, resulting in a longer half life (t1/2) and lower clearance. The approximate volume of distribution (aVd) and extrapolated peak concentration (Cp0) in the 3 groups were not different.

Effects of morphine and clonidine on sulphobromophthalein disposition in mice

Levels of sulphobromophthalein (BSP) in plasma and liver were elevated by the opiate, morphine, and by the alpha 2-adrenoceptor agonist, clonidine. Neither morphine, 1 mg kg-1, nor clonidine, 0.01 mg kg-1, affected BSP levels significantly. When given together at these doses, they caused BSP levels in plasma and liver to be raised. At 20 mg kg-1, the effect of morphine on BSP levels was maximal, as was that of clonidine, 1.0 mg kg-1. However, the effect of these drugs given together on plasma BSP exceeded the maximal effect of either alone. Yohimbine, an alpha 2-adrenoceptor antagonist, did not affect BSP levels, nor did the opiate antagonist, naloxone. Each of these antagonists reversed the hepatobiliary effects of its respective agonist, as shown by return of BSP levels to those of saline-treated mice. Yohimbine did not reverse morphine, nor did naloxone reverse clonidine. The additive effects of morphine and clonidine and the specificities of their respective antagonists strongly suggest the involvement of discrete receptors mediating their essentially identical hepatobiliary effects.

Urinary metabolites of caffeine in the premature infant

Caffeine metabolites in urine from premature infants were analysed by TLC and HPLC. Caffeine, dimethyluric acids, mono- and dimethylxanthines and, for the first time, a uracil derivative (6-amino-5-[N-methylformylamino]-1,3-dimethyluracil) were identified.

Effect of exercise and heat exposure on percutaneous absorption of methyl salicylate

The effects of exercise, heat exposure or both on the percutaneous absorption of methyl salicylate were studied in 6 healthy volunteers. Exercise was performed to 30% of VO2max, 45 min each hour for 6 h, at ambient temperatures of 22 degrees C or 40 degrees C. Systemic availability was assessed by measurement of plasma salicylate concentrations and cumulative urinary salicyluric acid excretion over an 8-h collection period. The absorption of methyl salicylate was increased to more than 3-times above control in subjects exercising in the heat. It is concluded that exercise and heat exposure, by increasing skin temperature, hydration and blood flow, enhance the percutaneous absorption of methyl salicylate.

Clonidine effects on sulfobromophthalein disposition in mice

Increasing doses of clonidine enhanced the retention of sulfobromophthalein (BSP) in plasma and liver, while reducing elimination of this dye into bile. The ED50 of clonidine for these effects was 0.05 to 0.2 mg/kg s.c. In clonidine-treated mice which were warmed to reverse drug-induced hypothermia, plasma and liver BSP levels were raised as compared to saline-treated mice. Clonidine also raised plasma and liver levels of the BSP analog, dibromosulfophthalein, which is not conjugated before biliary elimination. Hepatic glutathione levels, activity of glutathione-S-transferase and ratios of conjugated to unconjugated BSP were not affected by clonidine. In mice with cannulas in their common bile ducts to prevent duct spasm, clonidine reduced the amounts of BSP eliminated into bile. Thus, the alpha-2 adrenoceptor agonist, clonidine, raised plasma and liver levels of anionic dyes and reduced their levels in bile by mechanisms other than altered conjugation, hypothermia or bile duct spasm.

Opioid effects on lidocaine disposition and toxicity in mice

Morphine sulfate, 20 mg/kg, or equivalent doses of the opioids, meperidine and fentanyl, elevated plasma levels of lidocaine after i.v. administration of this antiarrhythmic drug. Plasma levels of the lidocaine metabolites, monoethylglycinexylidine and glycinexylidine, were reduced by opioids as lidocaine levels were elevated. The opioid antagonist, naloxone, 1 mg/kg, reversed the effects of morphine, 20 mg/kg, on lidocaine. After morphine, plasma levels of both lidocaine and indocyanine green were elevated, suggesting that the effect of morphine on lidocaine disposition was related to reduced hepatic blood flow. Morphine and meperidine increased lethality of i.v. lidocaine, as shown by marked reduction of LD50 by either opioid.

Opioid effects on hepatic disposition of dyes in mice

Morphine administration acutely reduced plasma clearance of sulfobromophthalein (BSP) in mice and increased hepatic retention of this dye. Increasing morphine doses from 5 to 40 mg/kg s.c. progressively raised plasma and liver BSP levels. Morphine-treated mice, warmed to reverse hypothermia, still had higher plasma and liver BSP levels. The narcotic also raised plasma levels of two dyes which are not conjugated, indocyanine green and dibromosulfophthalein. Naloxone reversed morphine-induced elevation of plasma BSP levels. In bile duct-ligated mice, plasma BSP levels were very high but hepatic BSP levels remained low, both after saline or morphine. Thus, the effects of morphine on BSP disposition differed from those of biliary occlusion. BSP content in bile was reduced by morphine, as dye levels were raised in plasma and hepatic parenchyma. In bile duct-cannulated mice morphine increased BSP levels in plasma and liver whereas reducing the amount of dye eliminated in bile.

Stridor caused by vocal cord malfunction associated with emotional factors

We describe two adolescent patients in whom a disorder of the vocal cords associated with emotional factors resulted in acute episodes of stridor. Adduction of the vocal cords on inspiration and abduction on expiration was found on indirect laryngoscopy. The problem responded to either placebo treatment or psychotherapy. The similarity between vocal cord dysfunction presenting as stridor and that presenting as asthma is discussed. The importance of diagnosing these functional problems in children is emphasized in order to avoid unnecessary diagnostic procedures and hazardous treatment.

The metabolism and excretion of 14C-styrene oxide-glutathione adducts administered to the winter flounder, Pseudopleuronectes americanus, a marine teleost. Identification of the corresponding S-cysteine derivatives as major urinary metabolites

The metabolism and excretion of intramuscularly administered 14C-glutathione conjugates of styrene oxide (Ia and IIa) were studied in the winter flounder at three dose levels. The various radiolabeled thioether metabolites excreted were separated by reverse-phase high pressure liquid chromatography, and identified and quantitated by cochromatography with synthetic standards. The urine was the major excretion route for radioactivity derived from the glutathione conjugates (up to 90%) at each dose level (1.0, 3.9, and 24.4 mg/fish) studied. The corresponding cysteine derivatives (Ic, IIc) were the major urinary metabolites although the N-acetylcysteine derivatives (Id, IId), or mercapturic acids, were also present in significant amounts at each dose and excretion interval examined. Unchanged glutathione conjugates of styrene oxide were the major radioactive constituents of 24-hr bile samples from the treated flounder, although significant amounts of the cysteinylglycine (Ib, IIb), cysteine, and N-acetylcysteine derivatives were also present in bile. Bile was a minor excretory route relative to urine. The oxidation of 14C-styrene to styrene 7,8-oxide by the cytochrome P-450-dependent monooxygenase system of hepatic microsomes of winter flounder was also demonstrated; likewise, styrene was converted to the diastereomeric glutathione conjugates of styrene 7,8-oxide by 9,000g supernatant fractions of flounder liver supplemented with glutathione. This study demonstrated that flounder liver can convert styrene to glutathione conjugates to styrene oxide and that mercapturic acid biosynthesis occurs after parenteral administration of a xenobiotic-glutathione adduct to this marine species, although the major urinary metabolites were the cysteine conjugates rather than the anticipated mercapturic acid derivatives.

Heterogeneity of hepatic aryl hydrocarbon hydroxylase activity in feral winter flounder: relevance to carcinogenicity testing

Hepatic microsomes from winter flounder (Pseudopleuronectes americanus), treated with polycyclic aromatic hydrocarbon (PAH) inducers, had elevated activities of benzo[alpha]pyrene hydroxylase (AHH) and 7-ethoxyresorufin deethylase (7-ERD). When electrophoresed, they showed a novel or enriched polypeptide species with a monomeric molecular weight of approximately 57,000. These results are consistent with inductive responses already well-characterized in several mammalian and fish species. However, when we studied the urinary clearance of 4-chlorobiphenyl in untreated flounder, wide variations (up to twentyfold) among fish were noted. Subsequent in vitro analysis of AHH and 7-ERD activities in liver demonstrated wide variations in these monooxygenase activities in flounder caught near Mount Desert Island, Maine. In some instances, AHH activities in these feral flounder were as high as those in PAH-induced fish. Based on the response of AHH activity to 7,8-benzoflavone (ANF) added in vitro, flounder could be divided into 2 groups; one had high hepatic AHH activity which was inhibited by ANF, the other had low AHH activity which was enhanced by ANF. Examination of a large number of winter flounder (greater than 400 total) over 4 experimental seasons demonstrated this variability of hepatic AHH activity to be a recurrent characteristic of the flounder population in waters around Mount Desert Island. The hepatic AHH activities did not correlate well with any physical parameter of the fish (e.g., liver, gonad or body weight, length, or sex) or the cytochrome P-450 content of the hepatic microsomes. Our attempt to evaluate the AHH activity (high vs. low) of individual fish in vivo by urinary clearance of antipyrine was unsuccessful, due to the excretion of large amounts of unchanged antipyrine through the gills. Similar studies were performed with another marine teleost, Fundulus heteroclitus. Of the approximately 200 Fundulus examined, almost all had AHH activity inhibited by ANF; in some experiments, hepatic 7-ERD activities were further increased after treatment with the potent PAH-type inducer 3,4,5,3',4',5'-hexachlorobiphenyl but only about twofold. Collectively, these data are consistent with PAH-type induction of the hepatic cytochrome P-450-dependent monooxygenase system in some feral marine teleosts (in winter flounder and Fundulus) from Maine by environmental contaminants or food constituents. It is not known whether these chemicals are of natural or anthropogenic origin. The variation in the response appears to be related to individual exposure level (dose) or sensitivity, or both.(ABSTRACT TRUNCATED AT 400 WORDS)