Tolerability and efficacy of IMpower133 regimen modified for dialysis patients with extensive-stage small cell lung cancer: Two case reports

The IMpower133 regimen, composed of atezolizumab/etoposide (VP-16)/carboplatin (CBDCA), is the standard first-line treatment for extensive-stage small cell lung cancer (ES-SCLC). However, the safety and efficacy of triplet therapy in patients receiving dialysis have not been sufficiently evaluated. Here, we report two cases of dialysis patients with ES-SCLC who received the modified IMpower133 regimen. Patient 1 was a 69-year-old man, and patient 2 was a 73-year-old man who received dialysis because of end-stage renal failure caused by diabetic nephropathy. Both patients received a modified IMpower133 regimen in the following order: atezolizumab (1200 mg/body) on day 1, VP-16 (50 mg/m² ) on days 1 and 3, and CBDCA (300 mg/m² ) on day 1. Four hours of dialysis was performed 1 hour after completing the administration of CBDCA on Day 1 and 2 hours after completing the administration of VP-16 on Day 3. Both patients achieved a partial response and received atezolizumab maintenance therapy after four cycles of triplet therapy without uncontrollable adverse events. By modifying the dosage, the order of drugs, and the timing of dialysis, the IMpower133 regimen may be tolerable and effective for patients receiving dialysis.

Hoxa3 regulates integration of glossopharyngeal nerve precursor cells

In vertebrates, certain Hox genes are known to control cellular identities along the anterior-posterior (A-P) axis in the developing hindbrain. In mouse Hoxa3 mutants, truncation of the glossopharyngeal (IXth) nerve or the fusion of the IXth and vagus (Xth) nerves was reported, although its underlying mechanism is largely unknown. To elucidate the mechanism of the IXth nerve defects, we reexamined the phenotype of Hoxa3 mutant embryos. In Hoxa3 mutants, we observed an abnormal caudal stream of the migrating Hoxa3-expressing neural crest cells at the prospective IXth nerve-forming area. Dorsomedial migration of the placode-derived neuronal precursor cells of the IXth nerve was also affected. Motor neurons at rhombomere 6 (r6), where those of the IXth nerve were positioned, often projected axons to the Xth nerve. In summary, the Hoxa3 gene has crucial roles in ensuring the correct axon projection pattern of all three components of the IXth nerve, i.e., motor neurons and sensory neurons of the proximal and distal ganglia.

Carcinogenicity test of polyoxyethylene(10) nonylphenyl ether (NP-10) in female B6C3F1 mice

A carcinogenicity study of polyoxyethylene(10)nonylphenyl ether (NP-10) to B6C3F1 mouse was performed using 50 females per group of 4 study groups, or 200 mice in total. Diets containing NP-10 at 0, 500, 1500 and 4500 ppm were prepared and orally administered to the animals repeatedly for 104 weeks, and observation of general conditions, body weight analysis, food consumption analysis, hematologic examination, organ weight analysis and pathological examination were performed. The results are summarized as follows. The mean intake of the test substance in the 500, 1500 and 4500 ppm groups for 104 weeks was 81.5, 254 and 873 mg/kg/day, respectively. There were no differences observed in mortality among the groups and the mortality did not exceed the background data in any groups. There were no signs attributable to the administration of the test substance, and various signs which increased in occurrence with aging were observed in all groups at a similar frequency. Body weight gain was suppressed only in the 4500 ppm group throughout the entire administration period. Food consumption was increased in all treated groups around the early stage of administration and, thereafter, in the 1500 and 4500 ppm groups until the mid-stage of administration. Decreased food efficiency was observed in the 4500 ppm group alone. As a result of the hematologic examination, no changes attributable to the administration of the test substance were observed in any groups. As a result of the organ weight analysis, lower absolute weights of the liver and kidney and higher relative weights of the brain, liver and kidney, which were considered to be changes accompanying the suppressed body weight gain, were observed in the 4500 ppm group. The pathological examination revealed no marked changes in the gross findings in the treated groups. As a result of the histological examination, there were no neoplastic or non-neoplastic lesions in the treated groups which were unequivocally observed to have increased in occurrence. As the above findings show, NP-10 did not cause any increase in the incidence of neoplastic lesions in the mouse by oral administration for 2 years at 873 mg/kg/day (4500 ppm) and was determined to have no carcinogenicity.

Oral chronic toxicity and carcinogenicity test of polyoxyethylene(10)nonylphenyl ether (NP-10) in female F344 rats

Chronic toxicity and carcinogenicity of polyoxyethylene(10)nonylphenyl ether (NP-10) to Fischer 344 rats were investigated using 70 females per group in 4 study groups, or 280 rats in total. Diets containing NP-10 at 0, 1000, 3000 and 9000 ppm were prepared and orally administered to the animals repeatedly for 52 weeks for a chronic toxicity study and for 104 weeks for a carcinogenicity study. Observations of general condition, body weight analysis, food consumption analysis, hematologic examination, blood chemistry examination (only at Week 52 of administration), urinalysis (only at Week 52), ophthalmologic examination (immediately prior to administration and at Week 52), organ weight analysis and pathological examination were performed. The results are summarized as follows. The mean intake of the test substance was 60.5, 182 and 559 mg/kg/day in the chronic toxicity study for 52 weeks and 55.2, 166 and 520 mg/kg/day in the carcinogenicity study for 104 weeks in the 1000, 3000 and 9000 ppm groups, respectively. Mortality decreased approximately in a dose-related manner, with 28% in the control group, 26% in the 1000 ppm group, and 14% each in the 3000 and 9000 ppm groups. In general condition, there were no signs attributed to the treatment with NP-10. Body weight gain was suppressed in the 9000 ppm group throughout the administration period and in the 3000 ppm group during Weeks 21-88. Food consumption decreased in the 9000 and 3000 ppm groups. Food efficiency was lower in the 9000 and 3000 ppm groups. As a result of the hematologic examination, hematocrit value, hemoglobin value, red blood cell count, platelet count and MCV were lower and MCH and MCHC higher in the 9000 ppm group at Week 52 of administration. At Week 104, the neutrophil ratio was higher and lymphocyte ratio lower in the 3000 and 9000 ppm groups, and furthermore, hematocrit value, hemoglobin value, MCV and MCH were slightly lower in the 9000 ppm group. In the blood coagulability tests, prothrombin time was slightly shortened in the 9000 ppm group at Week 52. As a result of the blood chemistry examination, total protein and albumin values were higher and total bilirubin, uric acid and trygliceride value lower in the 3000 ppm and higher dose groups. Furthermore, the free cholesterol value was higher and the values of potassium, cholesterol ester ratio, GOT, GPT, ALP and cholinesterase were lower in the 9000 ppm group. As a result of the urinalysis, the specific gravity of urine was higher and urine pH acidic in some animals. As a result of the ophthalmologic examination, no abnormal animals were found in the 9000 ppm group. As a result of the organ weight analysis, absolute and relative weights of the liver and adrenals were higher in the 3000 and/or 9000 ppm groups as changes which were considered attributable to the test substance and, in addition, organs with a lower absolute weight and higher relative weight with the suppressed body weight gain were observed in the 9000 ppm group. The histopathological examination revealed no marked findings in necropsy observation or histology in the treated groups in the animals killed at Weeks 52, 104 as well as those killed moribund and dead animals. In the histological findings, bile duct hyperplasia of liver in the animals killed at Week 52, proliferative duct of pancreas in the animals killed at Week 104, pigment of deposit in pituitary and angiectasis of adrenals in the animals killed at moribund and dead animals were observed in a slightly larger number in the treated groups, but none of these changes were different in degree from the control and were not considered to be specific lesions. As a result of the overall study of the neoplastic lesions of all animals killed on schedule and of moribund and dead animals, no tumors were found in the treated groups which had increased in occurrence. Based on the above findings, it was determined that the no-adverse-effect level in the chronic toxicity study was 1000 ppm (

Possibility of partial absorption of nicardipine by routes other than the hepato-portal system after oral administration in rats

The systemic availability of nicardipine after different routes of administration has been examined in rats, with particular attention to differentiating oral absorption from intestinal and hepatic metabolism. The quantities of nicardipine and its metabolite were determined by capillary column gas chromatography. A linear relationship was shown between the hepatic first-pass effect and dose after hepato-portal administration of nicardipine; the hepatic first-pass effect was calculated to be approximately 80%. However, the availability after oral and rectal administration was found to be more than twice that observed after hepato-portal administration. Partial avoidance of the hepatic first-pass effect after oral and rectal administration are estimated to be 37.3% and 35.2%, respectively, assuming that all absorbed molecules pass through the liver. These findings suggest that the absorption of nicardipine after oral administration also occurs by routes other than the hepato-portal system.

Participation of endodermal epithelial cells on the synthesis of plasma LDL and HDL in the chick yolk sac

We ultrastructually examined the chick yolk sac endodermal epithelium and evaluated our findings in combination with the biochemical analysis of serum and yolk lipoproteins. Twenty-five to 30 nm-sized particles were demonstrated to be a principal element of the extracellular yolk mass and these were determined to be yolk very low density lipoprotein (VLDL). The particles were shown to be taken up by the epithelial cells via coated pits and engulfed by plasma membrane invaginations together with yolk subdroplets, another element of the yolk mass. Through apical vacuoles, the two yolk elements were incorporated into yolk drops, which were identified to be one of the lysosomal structures by a cytochemical procedure using acid phosphatase (AcP)ase activity. During the last week of incubation, which is the final third of the incubation period, the digestion seemed to progress rapidly in the yolk drops, which came to resemble lipolysosomes; lipoprotein production became active as expressed by an enlarged Golgi apparatus. The newly produced lipoprotein particles were electron-lucent and irregular in size (50-120 nm). They were sequestered in secretory vacuoles and secreted from the vascular surface of the epithelial cells. Finally, the particles were thought to be taken into the vitelline circulation as plasma lipoproteins. The major component of lipoprotein in serum was determined to be low density lipoprotein (LDL) and high density lipoprotein (HDL), while cholesterol content was found to increase during incubation. We concluded that endodermal epithelial cells participate the synthesis of plasma LDL and HDL. For this synthesis the cells probably apply lipids and apo-protein generated from yolk VLDL degradation.

[A 52-week oral toxicity study of a new antineoplastic agent S-1 in dogs]

52-week oral repeated-dose S-1 toxicity studies were conducted. Male and female dogs were orally treated with 0, 0.1, 0.5 or 2.5 mg/kg/day for 52 weeks and permitted to recover for 13 weeks. Furthermore, to estimate the no-toxic dose, male and female dogs were given S-1 orally for 52 weeks at doses of 0, 0.004 and 0.02 mg/kg/day. The 2.5 mg/kg/day regimen produced one dead or moribund dog of each sex; black-brown patch (melanin deposition) and inflammatory changes in the eyes and skin; decreased in body weight gains; increases in MCV, MCH, monocyte ratio, and serum protein and uric acid; decreases in lymphocyte ratio and erythrocyte count, hematocrit, hemoglobin, albumin, A/G ratio, cholesterol (esterified, total and free), phospholipids, triglycerides, cholinesterase activity and creatinine; increases in relative liver and adrenal weights. Histopathological examinations revealed melanin deposits in superficial lymph nodes, increases in macrophage and plasma cell accumulation, and corneal atrophy accompanied by melanin deposits and capillary proliferation. A slight black-brown patch (melanin deposition) in the conjunctiva and skin was observed in the 0.1 and 0.5 mg/kg/day groups. No drug-related changes were observed in groups that received 0.02 and 0.004 mg/kg/day. All changes observed during the treatment period disappeared during recovery except for melanin deposits in the conjunctiva and superficial lymph nodes, corneal opacity, and a few hematological and blood chemistry parameters. In conclusion, the no-toxic dose in these 52-week studies was estimated to be 0.02 mg/kg/day.

Evaluation of antitumor activities of hyaluronate binding antitumor drugs: synthesis, characterization and antitumor activity

To enhance the selective delivery of antitumor drugs into regional lymph nodes and cancerous tissues via a hyaluronate (HA) receptor (CD44), we synthesized HA-mitomycin C complex and HA-epirubicin complex. To investigate the specific distribution of HA into regional lymph nodes and to evaluate the HA receptor on lewis lung carcinoma cells, we also synthesized 14C-labelled HA and fluorescent HA (FR-HA). The metabolic studies of 14C-HA and HA-epirubicin complex were performed in rats. The specific distribution of both compounds to the lymph nodes were observed after sc treatment. Internalization mechanisms of HA into carcinoma cells (lewis lung carcinoma) via HA receptor was investigated using fluorescent HA (FR-HA) in vitro. Internalization of FR-HA following binding to the cell surfaces was observed. HA-Mitomycin C (MMC) exhibited potent anti-metastatic effects against lewis lung carcinoma implanted in mice at an extremely low dose (0.01 mg/kg) whereas free MMC had no effects.

Formation and accumulation of lipolysosomes in developing chick hepatocytes

Formation and accumulation of lipolysosomes in developing chick hepatocytes were investigated by means of electron microscopy in combination with biochemical analyses of the lipid composition in liver homogenates. The lipolysosomes occurred with highest frequency from days 11 to 14 of incubation. They were usually small and electron-dense, but during development they gradually enlarged with an accompanying reduction in electron density. Coinciding with this enlargement was an accumulation of esterified cholesterol in the liver homogenates. After hatching, an immediate decrease in the size and number of lipolysosomes occurred along with a reduction in the concentration of esterified cholesterol, of which only a very small amount remained by 9 days of age. Instead of cholesterol, triglycerides subsequently increased in concentration and accounted for the major lipid content of the liver homogenates. In keeping with the ultrastructural changes, the total volume of cytoplasmic lipid droplets rapidly increased with increasing age. This transient accumulation of esterified cholesterol within lipolysosomes may be attributed to an excessive uptake and processing of plasma lipoprotein particles, probably derived from the egg yolk. This concept is supported by an abundance of coated pits, endosomes and multivesicular bodies in the embryonic hepatocytes.

Long-term survival of grafted cells, dopamine synthesis/release, synaptic connections, and functional recovery after transplantation of fetal nigral cells in rats with unilateral 6-OHDA lesions in the nigrostriatal dopamine pathway

In animal models of hemi-Parkinson's disease, survival of grafted nigral cells, their synaptic connections, dopamine (DA) synthesis/release, and recovery from motor disturbances were investigated, and these were compared among 3 groups of animals raised for 3 months, 1 year and 2 years after the transplantation. Fetal nigral DAergic cell suspensions were transplanted in the ipsilateral caudate nucleus of rats with unilateral 6-OHDA lesions in the nigrostriatal DA pathway. Motor disturbances, assessed by methamphetamine-induced rotation, recovered partly in the 2nd week, significantly in the 4th week after the grafting, and remained stable thereafter. Many tyrosine hydroxylase (TH)-positive cells were detected along the grafting tracks. The number of TH-positive cells was similar in the 3 groups of animals. These TH-positive cells made synaptic connections in the host caudate. By in vivo microdialysis measurement, extracellular DA, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) around the grafted sites recovered to 30-100% of those of controls. No significant differences were observed in the concentration of DA, DOPAC and HVA among 3 groups of animals. They also responded to methamphetamine loading though the magnitudes were smaller. Using a TH cDNA probe, TH-positive cells were found to express TH mRNA in in situ hybridization-autoradiographic analysis. Data indicate that grafted fetal DAergic cells survive, synthesize and release DA, make synaptic connections in the host brain and ameliorate motor disturbances for over 2 years. There were no differences in these parameters among the 3 groups of animals, and no untoward side effects were observed even at 2 years after the grafting. Thus it was confirmed that the grafting of neuronal cells into the brain is a promising approach to restore disturbed function.

Comparison of disposition parameters of quinidine and quinine in the rat

The difference in disposition of quinidine (Qd) and its diastereomer quinine (Qn) after intravenous administration was examined in rats at doses ranging from 5 to 20 mg/kg. Dose-dependent kinetics in total clearance and in distribution volume of tissue based on a two-compartment model was observed for Qd; there was no evidence of nonlinearity for Qn. However, there was no significant difference between Qd and Qn for blood clearance at doses of 5 and 10 mg/kg, at which the blood clearances were almost equal to hepatic blood flow for both Qd and Qn since the excretion of Qd and Qn into the urine and bile was minimal. This indicates the elimination of these diastereomers to be non-restrictive in the liver. A concentration dependence in unbound volume of tissue distribution and in plasma protein binding was observed for Qd; there was no concentration dependence for Qn. Although affinity of the drug for components on or within the blood cells was not concentration-dependent for either Qd or Qn, a significantly higher binding capacity for Qn than for Qd was observed attributable to blood cell binding. Based on these results, it is suggested that a larger number of binding sites exist for Qn than for Qd in the body. However, the dissociation binding constant for Qd is much lower than for Qn, resulting in a higher binding of Qd and Qn at low concentrations, with a reversal at high concentrations.

Determination of mean input time, mean residence time, and steady-state volume of distribution with multiple drug inputs

A general treatment for determination of mean residence time (MRT) and steady-state volume of distribution (Vss) after multiple drug inputs via any mode of administration is presented. For multiple inputs, either simultaneous or consecutive, the mean input time (MIT) can be readily calculated using the general equations presented here. Sample calculations for MIT, MRT, and Vss following different combinations of multiple drug inputs are presented. Errors inherent in noncompartmental area determinations are discussed.

Prediction of hepatic first-pass metabolism and plasma levels following intravenous and oral administration of barbiturates in the rabbit based on quantitative structure-pharmacokinetic relationships

Based on the concept of physiological pharmacokinetics, the hepatic first-pass metabolism and plasma levels following intravenous and oral administration of barbiturates in the rabbit was predicted based on the relationships between principle kinetic parameters and lipophilicity (chloroform-water partition coefficient). Good log-log linear relationships between kinetic parameters and lipophilicity were obtained for the seven barbiturates examined. The values of correlation coefficient were improved slightly by using the corrected values for partition coefficients of nonionic molecules in the cases of principle parameters such as drug-protein and drug-blood cell affinity, intrinsic hepatic clearance, and unbound volume of distribution. There was also a good linear relationship between absorption rate constant (mean absorption time) and lipophilicity. The mean hepatic transit time was negligible for the most lipophilic drug (hexobarbital) examined; this suggests that the mean absorption time for these barbiturates does reflect the absorption process. The available fraction in relation to hepatic first-pass metabolism was well predicted from the lipophilicity by both well-stirred and parallel-tube models, and the difference in the values predicted by both models was minimal. There were good relationships between predicted and observed values for plasma levels after intravenous and oral administration, except for two (cyclobarbital and phenobarbital) of the seven drugs used. The great difference between predicted and observed values for these two drugs was considered due to substituent effects in liver metabolism.

Simultaneous determination of nitroglycerin and its dinitrate metabolites by capillary gas chromatography with electron-capture detection

A sensitive gas chromatographic-electron-capture detection method for the simultaneous determination of the antianginal drug nitroglycerin (GTN) and its dinitrate metabolites (1,2-GDN and 1,3-GDN) was developed. Human plasma samples (1 ml) spiked with 2,6-dinitrotoluene as the internal standard were extracted once with 10 ml of a methylene chloride-pentane mixture (3:7, v/v). Using this solvent system, less contaminants are extracted into the organic phase from plasma, resulting in cleaner chromatograms and prolonged column life. A break point was observed on the standard curves of GTN and GDNs. The two linear regions for the detectable concentrations of GTN are 0.025-0.3 and 0.3-3 ng/ml and for 1,2-GDN and 1,3-GDN they are 0.1-1 and 1-10 ng/ml. The limits of detection by this method for GTN, 1,2-GDN and 1,3-GDN in plasma are 0.025, 0.1 and 0.1 ng/ml, respectively.

Pharmacokinetic study of carbamazepine and its epoxide metabolite in humans

A major metabolite of carbamazepine (CBZ), CBZ-10, 11-epoxide (EPO), has been reported to possess anticonvulsant properties. Therefore, the present study was undertaken in order to develop a pharmacokinetic model to predict the behavior of EPO in the body after administration of CBZ. The serum concentration-time curves after oral administration of solution of CBZ (200 mg) or EPO (150 mg) in six healthy subjects showed the characteristic "nose", suggesting that disposition of CBZ or EPO could be described by the two-compartment model. The kinetic parameters of disposition for CBZ and EPO were calculated by the method of Wagner, assuming the absolute bioavailabilities of CBZ and EPO to be 1.0 and 0.81, respectively. Total body clearance and elimination rate constant of EPO were very much larger than those of the parent drug but there was no statistically significant difference in the distribution volume between CBZ and EPO. The formation rate of EPO was calculated by a deconvolution method, and obeyed Michaelis-Menten kinetics. Based on these findings, a pharmacokinetic model of the fate of CBZ and EPO in humans was developed and the time courses of CBZ and EPO in serum after oral administration of three tablet preparations and a solution containing 200 mg of CBZ were simultaneously fitted to this model by solving the differential equations by the Runge-Kutta-Gill method. There was good agreement between calculated and observed serum values, suggesting that the present model is appropriate to describe the formation and disposition of EPO from CBZ. The formation rate constant of EPO (Vmax/Km/V1) was approximately one-fifteenth of the elimination rate constant of EPO. This suggested a flip-flop model in which the formation of EPO was rate-limiting in humans. The observation that the serum concentrations of EPO after administration of CBZ were one-tenth to one-twentieth of those of the parent drug was well explained by the flip-flop kinetics of EPO, together with the large differences in total body clearance and elimination rate constant between CBZ and EPO.

Study of the absorption site of cimetidine

The optimal absorption site of cimetidine was assessed in rats. The ileac pH value (measured by a pH meter with a micro pH combination electrode) was slightly higher than that in other intestinal sites, and the absorption rate constant (ka) following the administration of cimetidine into the ligated ileac loop was larger than that in the ligated duodenal and jejunal loops. It is suggested that the ileum is the optimal absorption site of cimetidine. On administration of cimetidine into the ligated and unligated intestines, the ka values of either the duodenum or the ileum were found to be almost the same between the ligated and unligated cases. However, the ka value of the jejunum in the unligated case was slightly larger than that in the ligated case. Thus, it is suggested that cimetidine is completely absorbed in the duodenum and ileum during its passage through these intestinal sites, but at the jejunum an unabsorbed fraction of cimetidine passes to the ileum, where it is absorbed completely. Based on these results, a pharmacokinetic model for the absorption of cimetidine following oral administration was designed, in which gastric, duodenal, jejunal, and ileac compartments were included separately but enterohepatic circulation was not included, because the biliary excretion of cimetidine following intravenous and oral administrations were generally lower than 2% of the dose. The value of k41 was ca. 4 times larger than that of k45, and the value of k45 could be approximated to zero in the model.

Enhancement of RNA synthesis in chick liver by food intake: possible role of high mobility group nonhistone proteins

RNA synthesis in the nuclei of liver from newly hatched (4-d-old) chicks is enhanced by intake of food. The enhanced synthesis was ascribed not to an increase in the activity of solubilized DNA-dependent RNA polymerase but to an increase in the initiation of RNA synthesis. Enhanced RNA synthesis in fed chicks was accompanied by greater susceptibility of nuclei to digestion by micrococcal nuclease. Salt extraction abolished the difference in nuclease sensitivity between the fed and fasted groups. Reconstitution with either 0.35 M NaCl extracts or high mobility group (HMG) nonhistone proteins restored digestion susceptibility, but changing the source of extracted proteins did not equalize the extent of digestion in nuclei from livers of fed and fasted chicks. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of HMG proteins revealed the presence of HMGs 1 and 2 as well as a 38,000-dalton protein. The nuclear HMG protein content in fed chicks was greater than that of fasted chicks (121 +/- 17 micrograms/mg DNA vs. 31 +/- 12 micrograms/mg DNA). The electron microscopic examination of hepatocyte nuclei revealed the enlargment of nucleoli and scarcity of aggregated heterochromatin structures in the fed chicks as compared with the fasted chicks. These morphological features are compatible with the high transcriptional activity in liver of fed chicks.

Dose- and time-dependent kinetics of the renal excretion of nitrofurantoin in the rabbit

A pharmacokinetic study on the renal excretion of nitrofurantoin was carried out in rabbits at doses ranging from 0.5 to 15 mg/kg. With increasing dose, nonlinear kinetics were observed in the tubular secretion, which appeared to show dose and time dependence. The disposition of nitrofurantoin after intravenous injection is well described by a one-compartment model with simultaneous first-order nonrenal elimination and renal elimination, which consists of glomerular filtration, active tubular secretion conforming to the Michaelis-Menten equation, and reabsorption clearance by nonionic diffusion. Plasma and urinary excretion data after intravenous injection of nitrofurantoin were fitted to this model. When the Michaelis constant was loosely restricted at a constant value, the maximum velocity decreased with increasing dose of nitrofurantoin. However, the Michaelis constant apparently increased with increasing dose when the maximum velocity was loosely restricted at a constant value. Although the results of this fitting suggested that the former case may occur in the active tubular secretory system, the latter case could not be completely eliminated because of limited data. The implications of these results are discussed on the basis of the available published data.

Pharmacokinetic study of the enterohepatic circulation of acetaminophen glucuronide in rats

A pharmacokinetic model of the enterohepatic circulation of acetaminophen glucuronide was investigated in rats with particular attention to a lag time between biliary excretion and reabsorption. The plasma drug data obtained after acetaminophen glucuronide injection into the various sites of the gut confirmed that there is a lag time in the enterohepatic circulation and that the lag time is due to the intestinal transit period of the conjugate to the site of the hydrolysis. The value of the lag time was fairly close to that reported previously in the rat. Based on the result, a compartment model with periodic trigonometric function for the enterohepatic circulation was built up and the urinary excretion data were fitted to this model. Same parameters which are considered to be common to other glucuronide conjugates were in good agreement with those reported previously, indicating that the model and those values are useful to study the enterohepatic circulation for glucuronides of other compounds in the rat.

Prediction of blood levels following oral administration of weakly acidic drug particles such as sulfa drugs in rabbits from the in vitro dissolution behavior

Prediction of blood levels following oral administration of weakly acidic drug particles such as sulfa drugs from data obtained in in vitro dissolution tests of drug suspensions was studied in the rabbit. The relationship between in vivo and in vitro dissolution rates or between absorption rate and in vitro dissolution rate was investigated. The drug absorption from aqueous solution was suggested to be rate-limited by the gastric emptying rate because the initial absorption rate constant in a biexponential time course of aqueous solution for the amount unabsorbed vs. time plot was almost the same among 9 of the 10 drugs tested, except for sulfacetamide. This indicated that when the in vivo dissolution rate constant is much slower than the initial absorption rate constant of aqueous solution, the time course of blood levels for the solid drug will deviate from that of aqueous solution. Based on the consideration, the critical in vitro dissolution rate constant corresponding to the initial absorption rate constants of aqueous solution was calculated by means of statistical analysis using the relationship between in vivo and in vitro parameters. The validity of this prediction was examined using four high-solubility drugs, and it was found that the prediction could be done whether the in vitro dissolution medium was distilled water or 0.1 N HCl solution. Although in the present study, the experiment was done using an aqueous suspension form in the rabbit, the applicability of this prediction method to other dosage forms and to the case of humans is discussed.

Nonlinear assessment of nitrofurantoin bioavailability in rabbits

The influence of route of administration on the absolute bioavailability and GI tract absorption of nitrofurantoin was investigated in rabbits. The disposition of nitrofurantoin was described by a one-compartment model with simultaneous first-order and Michaelis-Menten type elimination kinetics, and bioavailability was estimated by nonlinear assessment. The plasma levels following oral administration were significantly lower than those after intravenous administration, and absolute F values for oral administration were approximately 0.3. However, F values following intraduodenal administration and portal vein infusion were nearly unity, and it was concluded that the reduction of bioavailability following oral administration could not be attributed to metabolism by intestinal microflora or to the hepatic first-pass effect. Thus, reduction of F values following oral administration is probably due to gastric degradation of the drug. The effects of factors influencing bioavailability, such as water volume taken with the drug, change of gastric emptying rate and effect of particle size, were also investigated. Increase of volume of water administered tended to improve the bioavailability, and a particle size dependency was also observed.

Pharmacokinetic study of the fate of acetaminophen and its conjugates in rats

Pharmacokinetic studies of the fate of acetaminophen and its major metabolites, acetaminophen sulfate (AS) and acetaminophen glucuronide (AG), were made in rats. The rates of conjugate formation were calculated by deconvolution. The Michaelis-Menten equation gave maximum velocity and Michaelis constant (Km) values of 4.92 mumol/min/kg and 109 microM for AS formation, and 2.76 mumol/min/kg and 915 microM for AG formation. However, AG formation showed approximately first-order behavior in the present dose range because of its large Km value. The disposition of acetaminophen could be described by a two-compartment model with simultaneous first-order and Michaelis-Menten type elimination kinetics for AS formation. Curve fitting of the data based on this model was successfully done for doses of up to 1058 mumol/kg, suggesting that sulfation proceeds without depletion of sulfate in the blood at least up to this dose. The disposition of AS could be described by a two-compartment model and was apparently dose-independent over an 8-fold dose range. Although a slight dose dependence in the elimination of AG was suggested over a 16-fold dose range, for the purpose of the present study, it was assumed that the disposition of AG is approximately linear. The excretion of AS in the bile was negligibly small, whereas a considerable amount of AG was excreted into the bile. The results following intraduodenal injection of AS or AG indicated that AS or AG was hydrolyzed by the microflora and the liberated acetaminophen was reabsorbed, confirming enterohepatic circulation of the conjugates. This was consistent with the urinary metabolite excretion patterns observed after acetaminophen injection in normal and bile fistula rats. Based on the kinetic parameters obtained, the plasma concentrations of AS and AG after acetaminophen injection were simulated, and a fairly good agreement was obtained between calculated and observed values at the dose of 264.6 mumol/kg. Although the urinary metabolite excretion pattern differs from that of humans, the kinetic parameters obtained for rats were similar to those for humans in some respects, suggesting that the rat might be useful as a model animal to predict human data.

[A study of caerulein action on secretory cells, especially in the islets of Langerhans in the rat pancreas (author's transl)]

Although it is known that caerulein exerts an action on the secretory activity of the islets of Langerhans in the pancreas, the mechanism of this hormone has not yet been ascertained. The present investigation was undertaken to observe the ultramicroscopic changes of the pancreatic islets and the peripheral blood levels of insulin, glucagon, glucose and electrolites after caerulein administration. The animals were divided into four groups, and three were injected intraperitoneally with caerulein at 25 micrograms/kg, 2 micrograms/kg and 0.2 microgram/kg body weight, respectively. The fourth group served as the control. In the first group (25 micrograms caerulein), the endocrine cells of the pancreatic islets showed accelerated functioning immediately and up to about 2 hours after injection. Then these cells degenerated due to cytoplasmic edema and evidenced decreased secretory activity. In the second group (2 micrograms) depression in the secretory activity occurred for about 2 hours immediately after the injection, but there was no destruction of cells and they gradually recovered their functioning. The third group (0.2 microgram) displayed an acceleration of secretory activity immediately after the injection and then recovered to the normal state. There were some changes of electrolites in the peripheral blood in each of the three groups, suggesting that caerulein causes acceleration and depression of the secretory activities in the islets of Langerhans in the pancreas depending on the dosage. Moreover, the cell alterations may well depend on the changes of electrolites in the inner and outer atmospheres of the cells.

Fluorescence assay of nitrofurantoin with o-aminothiophenol in plasma and urine

A fluorescence method is presented for the determination of nitrofurantoin based on conversion of the drug to a fluorescent substance. The method requires 0.1-0.5 ml of plasma or diluted urine and is 10 times more sensitive than the commonly used colorimetric method.

[Electron microscopical observations on the curative effect of ursodesoxycholic acid in alloxan-induced pancreatic islet cell injury (author's transl)]

The preventive effect of ursodesoxycholic acid on pancreatic injury by alloxan (alloxan diabetes) has been reported by Watari, et al. (1976). In the following experiment, to pursue the findings further, ursodesoxycholic acid was used curatively for alloxan diabetes. A first group of animals (5 mice) were injected with alloxan (4 mg) twice at the fifth and tenth day. The second group (5 mice) was injected with ursodesoxycholic acid (0.2 mg each) for 14 days during the experiment in addition to the same alloxan dosage/frequency as the first group. A third group of animals (5 mice) served as the control. The animals were sacrificed on the 15th day and the blood sugar levels were examined, using commercial test paper. The pancreatic tissues were fixed in a mixture of 2.5% glutaraldehyde and 2% osmid acid solution, which was adjusted at pH 7.4 with a veronal acetate buffer; the osmotic pressure was also regulated by adding sucrose of 0.045 g/ml. Following dehydration using a series of alcohol concentrations, the tissues were embedded in Epon 812. Thin sections were cut with a Porter-Blum MT-2B ultramicrotome, stained with both uranyl acetate and a lead mixture, and then observed by electron microscopy. The results were as follows: The pancreatic islet cells, especially of B-cells in the first group of animals injected with alloxan only, were seriously damaged and contained myelinated mitochondria. Golgi apparatus, and an increasing number of autophagic vacuoles. Some B-cells revealed hydropic degeneration. Some B-granules changed into vacuoles after diacrine secretion. Pancreatic A-cells were increased in number and showed no cell injuries. On the other hand, the pancreatic B-cells of mice treated with both alloxan and ursodesoxycholic acid maintained almost normal fine structures. In summary, ursodesoxycholic acid has a curative effect on alloxan-induced pancreatic B-cell injury.

Comparative light and electron microscopic study of the adrenal gland of the snake

A new method employing both comparative light and electron microscopic observations on the study of identical cell elements was described. This method was characterized by the use of thick Epon-embedded sections (0.3-1.5 micron thick) for both light and electron microscopy. The use of a high voltage electron microscope of 1,000 kV accelerating potential made this study possible. Two types of chromaffin cells were distinguished in the adrenal gland of the snake, Elaphe quadrivirgata. Adrenaline storing (A) cells were found to be filled with slightly irregular, larger electron-dense granules, whereas noradrenaline-storing (NA) cells contained smaller granules with an electron-dense content. It was found that the chromaffin cells of the snake possess axon-like cytoplasmic processes.