The role of 3-methylsulfonyl-2,2',4',5,5'-pentachlorobiphenyl, a metabolite of 2,2',4,5,5'-pentachlorobiphenyl, in the induction of hepatic microsomal drug-metabolizing enzymes by 2,2',4,5,5'-pentachlorobiphenyl in rats

After the administration of 2,2',4,5,5'-pentachlorobiphenyl (2,2',4,5,5'-pentaCB) to intact rats, the concentration of 2,2',4,5,5'-pentaCB in liver gradually decreased, whereas 3-methylsulfonyl (3-MeSO(2))-2,2',4',5,5'-pentaCB appeared in liver and remained detectable in liver for 6 weeks. A single injection of 2,2',4,5,5'-pentaCB (342 μmol/kg) or 3-MeSO(2)-2,2',4',5,5'-pentaCB (0.5 μmol/kg) caused a significant increase both in the contents of cytochromes P450 and b(5) and in the activities of aminopyrine N-demethylase and benzo[a]pyrene hydroxylase, and the increased enzyme contents and activities continued for 6 weeks after the administration. The extent of both the hepatic accumulation of 3-MeSO(2)-2,2',4',5,5'-pentaCB and the induction of the enzymes for 6 weeks after the administration of 2,2',4,5,5'-pentaCB was similar to that after the administration of 3-MeSO(2)-2,2',4',5,5'-pentaCB. 3-MeSO(2)-2,2',4',5,5'-pentaCB was considered to play a principal role in the induction of microsomal drug-metabolizing enzymes by 2,2',4,5,5'-pentaCB. When 2,2',4,5,5'-pentaCB was injected i.p. into bile duct-cannulated rats, 3- and 4-MeSO(2)-2,2',4',5,5'-pentaCBs were not detected in liver. In antibiotic-treated rats dosed with 2,2',4,5,5'-pentaCB, the concentrations of 3- and 4-MeSO(2)-2,2',4',5,5'-pentaCBs in liver were markedly reduced. These findings suggest that the process in which 3- and 4-MeSO(2) metabolites of 2,2',4,5,5'-pentaCB are formed involves the biliary secretion of some precursors which will be subjected to metabolism by intestinal microflora. The increasing effects of 2,2',4,5,5'-pentaCB both on the content of cytochrome P450 and on the activity of aminopyrine metabolizing enzyme in hepatic microsomes were not observed in the bile duct-cannulated rats, in which the phenobarbital treatment enabled the drug-metabolizing enzymes to be induced. In antibiotic-treated rats, the increases both in the cytochrome P450 content and in the aminopyrine N-demethylase activity after the administration of 2,2',4,5,5'-pentaCB were smaller than those observed in the intact rats. These findings provide the evidence that the induction of some drug-metabolizing enzymes by 2,2',4,5,5'-pentaCB is due not to the action of 2,2',4,5,5'-pentaCB itself but to its 3-methylsulfonyl metabolite, 3-MeSO(2)-2,2',4',5,5'-pentaCB.

In vivo receptor occupancy and plasma concentration of pranidipine, a potent and long-acting dihydropyridine calcium antagonist

The occupancy of 1,4-dihydropyridine (DHP) receptors by pranidipine was characterized in tissues of spontaneously hypertensive rats (SHR). Oral administration of pranidipine (1 and 3 mg/kg) in SHR produced significant (26-67%) decreases in the number of specific (+)-[(3)H]PN 200-110 binding sites (B(max)) with 2- to 4-fold increases in the apparent dissociation constant (K(d)) in myocardial tissues at 1, 3 and 6 h later. In these rats, there was a reduction (16-37%) of B(max) in cerebral cortical (+)-[(3)H]PN 200-110 binding. Occupancy of myocardial DHP receptors after oral administration of pranidipine correlated well with its plasma concentration. Oral administration of nifedipine (10 mg/kg) in SHR caused significant increase in K(d) values for (+)-[(3)H]PN 200-110 binding in myocardium and cerebral cortex at 1 h later. In vivo specific (+)-[(3)H]PN 200-110 binding in particulate fractions of SHR aorta was markedly (59-78%) reduced at 1, 3 and 12 h after oral administration of pranidipine (3 mg/kg), while myocardial (+)-[(3)H]PN 200-110 binding was decreased by 46-48% at 1 and 3 h later. In these rats, there was a significant decrease (34%) in cerebral cortical (+)-[(3)H]PN 200-110 binding at 3 h later. In contrast, nifedipine administration produced a similar degree of reduction (71-84%) of in vivo (+)-[(3)H]PN 200-110 binding in the myocardium, aorta and cerebral cortex. It is concluded that pranidipine may exert more selective and sustained occupation in vivo of DHP receptors in vascular tissues of SHR than in myocardial and brain tissues.

Comparability testing of a humanized monoclonal antibody (Synagis) to support cell line stability, process validation, and scale-up for manufacturing

Biochemical and functional testing of a humanized monoclonal antibody directed against Respiratory Syncytial Virus (Synagis) has been performed to evaluate cell line stability, support process validation, and to demonstrate "comparability" during the course of process development. Using a variety of analytical methods, product manufactured at different sites and in bioreactors from 20 litres to 10,000 litres was shown to be biochemically and functionally equivalent. The biochemical testing for microheterogeneity found on Synagis included evaluation of changes in post-translational modifications such as deamidation, truncation, and carbohydrate structure. Studies were also performed to support cell line stability assessment and cell culture process validation. Cell culture conditions were deliberately varied in an attempt to determine if this would have an impact on the microheterogeneity of the product. In these studies Synagis was produced from cells cultured beyond the population doublings achieved at the maximum manufacturing scale, under conditions of low glucose, and using harvest times outside of the historical manufacturing operating range. Results showed that there was a different pattern of glycosylation during the early stages of bioreactor culture. No other changes in microheterogeneity were apparent for the other culture conditions studied. In summary, comparability assessment demonstrated that the Synagis manufacturing process is robust and consistent resulting in a predictable and reproducible monoclonal antibody product.

Synthesis of conformationally restricted analogs of baclofen, a potent GABAB receptor agonist, by the introduction of a cyclopropane ring

Conformationally restricted analogs of baclofen (2), i.e., 5, 6, and their enantiomers ent-5, and ent-6, the conformations of which were restricted by introducing a cyclopropane ring, were designed as potential GABAB receptor ligands. Reaction of (R)-epichlorohydrin [(R)-7] and (4-chlorophenyl)acetonitrile in the presence of NaNH2 in benzene/tetrahydrofuran gave chiral cyclopropane derivatives 11 and 12, which were then converted into the target compounds 5 and 6, respectively. Their corresponding enantiomers, ent-5 and ent-6, were also synthesized starting from (S)-epichlorohydrin [(S)-7].

Tissue distribution of methylsulfonyl metabolites derived from 2,2',4,5,5'-penta- and 2,2',3,4',5',6-hexachlorobiphenyls in rats

The time courses of fecal excretion and tissue distribution of metabolites derived from 2,2',4,5,5'-pentachlorobiphenyl (CB101) and 2,2',3,4',5',6-hexachlorobiphenyl (CB149) were investigated in male Wistar rats. The metabolism of both congeners involved primarily hydroxylation at the 3-position, and methylthiolation at the 4-position. Metabolites distributed in tissue were dominated by different ratios of 3- and 4-methylsulfonyl (MeSO2) metabolites. The 3-/4-MeSO2 metabolite ratios in liver and adipose tissue for both congeners were 0.41-0.61 at day 4, and then increased to 0.85-1.00 for up to day 42. In contrast, the ratios in lung were 0.03-0.04, and then decreased to 0.01. Compared to the unchanged PCBs at day 42, the distribution ratios of 3-MeSO2 metabolites were greater in the order of liver (0.46 for CB101 and 0.21 for CB149) > kidney > blood > lung > adipose tissue, whereas those of 4-MeSO2 metabolites were in the order of lung (9.50 for CB101 and 4.00 for CB149) > kidney > blood > liver > adipose tissue, indicating the different binding affinity of 3-MeSO2 metabolites in liver from that of 4-MeSO2 metabolites in lungs of rats. Furthermore, the structure-tissue affinity relationship for 3-MeSO2 metabolites was investigated, following the administration of 11 3-MeSO2-PCB congeners to rats. The results indicated that the retention potential of 3-MeSO2 metabolites in the liver largely depends on the ortho-chlorine substitution in the biphenyl ring rather than the degree of chlorination.

Ex vivo and in vivo alpha1-adrenoceptor binding characteristics of a novel alpha1L-adrenoceptor antagonist, JTH-601, in rat tissues

In vitro, ex vivo and in vivo alpha1-adrenoceptor binding of JTH-601 (3-[N-[2-(4-hydroxy-2-isopropyl-5-methylphenoxy)ethyl]-N-methylaminometh yl]-4-methoxy-2,5,6-trimethyl-phenol hemifumarate), a novel alpha1L-adrenoceptor antagonist, in rat tissues was investigated. JTH-601 competed in a concentration-dependent manner with [3H]prazosin for binding sites in the prostate, submaxillary gland and spleen of rats in vitro, and the inhibitory effect was not largely different among these tissues, as shown by the Ki values of 2-3 nM. At 0.25, 0.5 and 3 h after oral administration of JTH-601 (6.5 micromol/kg) in rats, there was a significant (57, 64 and 28%, respectively) increase in the apparent dissociation constant (Kd) for prostatic [3H]prazosin binding, compared to the control value. The administration of a higher dose (21.8 micromol/kg) of this agent produced greater (67-99%) increases in Kd values for prostatic [3H]prazosin binding at 0.5-12 h later. Similar significant increases in Kd values, as with the prostate, were seen in the submaxillary gland and heart 0.25-12 h after the oral administration of JTH-601 (6.5 and 21.8 micromol/kg), but significant increases in the spleen and cerebral cortex were seen only at 0.25-3 h and 0.5 h, respectively. At 10 min of i.v. injection of [3H]JTH-601 in rats, in vivo specific binding was observed in the prostate, cerebral cortex, submaxillary gland, spleen and heart but not in the aorta. The binding in the prostate, submaxillary gland and heart, but not in the cerebral cortex and spleen, lasted until 120 min. It is concluded that JTH-601 may exert a considerably sustained blockade of alpha1-adrenoceptors in the prostate of rats. This finding may be important in characterizing the therapeutic effect of JTH-601 for bladder outlet obstruction in patients with benign prostatic hyperplasia.

Effects of TH-142177 on angiotensin II-induced proliferation, migration and intracellular signaling in vascular smooth muscle cells and on neointimal thickening after balloon injury

We investigated the effects of TH-142177 (N-n-butyl-N-[2'-(1-H-tetrazole-5-yl) biphenyl-4-yl]-methyl-(N-carboxy methyl-benzylamino)-acetamide), a novel selective antagonist of angiotensin II type 1-receptor (AT1-R) on angiotensin II (AII)-induced proliferation and migration of vascular smooth muscle cells (VSMC), and on neointimal formation in the rat carotid artery after balloon injury, and on the intracellular signaling by the stimulation of AT1-R. High affinity AII receptor sites were detected in rat VSMC by the use of [125I]Sar1,Ile8-AII. TH-142177 and losartan competed with [125I]Sar1,Ile8-AII for the binding sites in VSMC in a monophasic manner, although PD123177, a selective antagonist of angiotensin II type 2-receptor (AT2-R), had little inhibitory effect, demonstrating the predominant existence of AT1-R in rat VSMC. TH-142177 prevented AII-induced DNA synthesis and migration, with a significant inhibition of 74 and 55%, respectively, at the concentration of 100 nM. AII-induced activation of p21ras, mitogen-activated protein kinase (p42MAPK and p44MAPK), and protein kinase C was significantly (50-78%) inhibited by TH-142177 (100 nM), suggesting that the activation of these enzymes is mediated through the stimulation of AT1-R. Balloon-injured left carotid arteries in rats showed extensive neointimal thickening, and TH-142177 (3 mg/kg) brought out a marked decrease in the neointimal thickening after balloon injury. In conclusion, TH-142177 inhibited AII-induced proliferation and migration of rat VSMC and neointimal formation in the carotid artery after balloon injury, and these effects may be related, in part, to the suppression of ras, p42MAPK and p44MAPK, and protein kinase C activities through the blockade of AT1-R. Thus, TH-142177 may have therapeutic potential for the treatment of vascular diseases such as atherosclerosis and restenosis.

In vivo measurement by [3H]Tamsulosin of alpha1 adrenoceptors in rat tissues in relation to the pharmacokinetics

The present study was undertaken to simultaneously measure alpha1 adrenoceptors in rat tissues by [3H]tamsulosin in vivo. In vivo specific [3H]tamsulosin binding was observed in the prostate, vas deferens, aorta, submaxillary gland, spleen, heart, lung, and kidney after i.v. injection of the ligand but not in the cerebral cortex and liver. Specific [3H]tamsulosin binding in the kidney, lung, heart, and spleen was greatest at 3 min after i.v. injection and declined rapidly with the disappearance of [3H]tamsulosin from the plasma. On the other hand, [3H]tamsulosin binding in the prostate and aorta peaked at 10 to 60 min after i.v. injection, and a considerable level of specific binding in both tissues persisted up to 240 min. The most sustained binding of [3H]tamsulosin occurred in the submaxillary gland. In vivo specific [3H]tamsulosin binding in rat tissues was effectively inhibited by the coinjection of low doses of unlabeled tamsulosin, prazosin, and terazosin with the radioligand but not by relatively high doses of yohimbine and propranolol. Based on estimated ID50 values, in vivo inhibitory effect of tamsulosin compared with prazosin was 5 to 14 times greater in rat tissues except the spleen, which showed 1.6 times less potent than prazosin. From ratios of ID50 (spleen) to ID50 (submaxillary gland) or ID50 (prostate), tamsulosin was 9 and 19 times, respectively, greater than prazosin in selectivity of alpha1 adrenoceptors in the submaxillary gland and prostate versus the spleen, respectively, suggesting that tamsulosin binds to alpha1A subtype with higher affinity than alpha1B subtype in vivo. The present study suggests that [3H]tamsulosin is a useful radioligand for in vivo measurement of alpha1 adrenoceptors in rat tissues.

[Metabolism of 3,3',4,4',5-penta- and 2,2',3,3',4,4'-hexachlorobiphenyls in rats]

Following the i.p. administration of 3,3',4,4',5-pentachlorobiphenyl (CB126) and 2,2',3,3',4,4'-hexachlorobiphenyl (CB128) to rats, blood, liver, lung, kidney, adipose tissue and feces were analyzed for the metabolites. CB126 was biotransformed to three hydroxylated metabolites identified as 4-OH-3,3',4',5'-tetraCB, 4-OH-3,3',4',5,5'-pentaCB and 5-OH-3,3',4,4',5'-pentaCB at about 1:7:2 ratio, whereas to two methylthio metabolites as 5-MeS- and 6-MeS-3,3',4,4',5'-pentaCBs at 1:2 ratio. Among the metabolites, only 4-OH-3,3',4',5,5'-pentaCB was detected in all tissues and blood. The ratio of metabolite/unchanged CB126 was 1:1.3 in blood and 1:162 in liver, indicating the high blood affinity of this metabolite. Trace amounts of 5-methylsulfonyl-3,3',4,4',5'-pentaCB was also detected in the liver. CB128 was biotransformed to 5-OH-, 5-MeS- and 6-MeS-2,2',3,3',4,4' hexaCBs which were excreted to feces in about 5:5:1 ratio. No metabolites were detected in blood and any tissues except for liver where trace amounts of 5-hydroxylated metabolite was present, indicating the low tissue affinity of hydroxylated metabolites from CB128.

Comparative study on pharmacokinetics and in vivo alpha1-adrenoceptor binding of [3H]tamsulosin and [3H]prazosin in rats

The plasma concentration, total radioactivity and in vivo alpha1-adrenoceptor binding in rat tissues after intravenous (i.v.) injection of [3H]tamsulosin were measured and they were compared with those obtained after the injection of [3H]prazosin. The plasma concentration of [3H]tamsulosin was consistently higher than that of [3H]prazosin, with 1.4 times greater areas under the curve (AUC(0-infinity)) of plasma concentration. As there was a significantly lower value of apparent volume of central compartment (Vd(c)) and distribution volume at steady state (Vd(ss)) for [3H]tamsulosin than [3H]prazosin with little difference in elimination rate constant (beta), the higher concentration of [3H]tamsulosin in plasma might be associated mainly with the smaller volume of distribution. The ratio of total radioactivity in tissues to the plasma unbound concentration of [3H]tamsulosin after i.v. injection of the ligand was consistently lower than that of [3H]prazosin. These observations suggest that [3H]tamsulosin is distributed in rat tissues in a more limited manner than [3H]prazosin. A significantly lower level of in vivo specific binding of [3H]tamsulosin than [3H]prazosin was observed in the spleen, heart and liver. Further, the apparent dissociation constant (Kd) and maximal number of binding sites (Bmax) for in vivo specific [3H]tamsulosin binding were considerably lower than those for [3H]prazosin binding. Therefore, these findings suggest that [3H]tamsulosin labels preferentially a subpopulation of the alpha1-adrenoceptor sites in rat tissues labeled by [3H]prazosin. In conclusion, the present study has shown that there is a significant difference in the pharmacokinetics and in vivo alpha1-adrenoceptor binding characteristics between tamsulosin and prazosin.

Reduction of thyroid hormone levels by methylsulfonyl metabolites of tetra- and pentachlorinated biphenyls in male Sprague-Dawley rats

Male Sprague-Dawley rats received four consecutive intraperitoneal (i.p.) doses of five kinds of methylsulfonyl (MeSO2) metabolites of tetra- and pentachlorinated biphenyls (tetra- and pentaCBs) to determine their effects on thyroid hormone levels. The five MeSO2 metabolites, which were the major MeSO2-PCBs detected in human milk, liver and adipose tissue were 3-MeSO2-2,2',4',5-tetraCB (3-MeSO2-CB49),3-MeSO2-2,3',4',5-tetraCB (3-MeSO2-CB70), 3-MeSO2-2,2',3',4',5-pentaCB (3-MeSO2-CB87), 3-MeSO2-2,2',4',5,5'-pentaCB (3-MeSO2-CB101), and 4-MeSO2-2,2',4',5,5'-pentaCB (4-MeSO2-CB101). All five tested MeSO2 metabolites (20 mumol/kg once daily for 4 days) reduced serum total thyroxine levels 16-40% on days 2, 3, 4, and 7 (after the last dosage). The total triiodothyronine level was reduced 37% by treatment with 3-MeSO2-CB49 at day 7, but was increased 35% and 38% by 3-MeSO2-CB70 and 4-MeSO2-CB101 at days 3 and 4, respectively. The reductions in thyroid hormone levels led to an increase in thyroid stimulating hormone (TSH) levels by 3-MeSO2-CB49, 3-MeSO2-CB87 and 3-MeSO2-CB101. A 30% increase in thyroid weight was produced by 3-MeSO2-CB101 treatment. Thus, it is likely that all five tested MeSO2 metabolites could influence thyroid hormone metabolism. The results show that the tested 3- and 4-MeSO2 metabolites of tetra- and pentaCBs reduce thyroid hormone levels in rats, suggesting that the metabolites may act as endocrine-disrupters.

Brain proton magnetic resonance spectroscopy and brain atrophy in myotonic dystrophy

OBJECTIVES

To evaluate by magnetic resonance spectroscopy the age-related cerebral alterations present in myotonic dystrophy (MD) and to compare these results with those obtained by magnetic resonance imaging.

DESIGN

Twenty-one patients (aged 16-63 years) with MD were compared with 16 age-matched healthy control subjects.

RESULTS

In magnetic resonance spectroscopy, the mean (+/- SD) ratio of N-acetylaspartate to creatine and phosphocreatine in the patients with MD (1.09 +/- 0.32) was significantly lower than that in the control subjects (1.93 +/- 0.43) (P<.001). The mean ratio of N-acetylaspartate to choline-containing compounds in the patients with MD (1.70 +/- 0.44) was also significantly lower than that in the control subjects (2.75 +/- 0.53) (P<.001). These changes could be observed already in the younger patients. In magnetic resonance imaging, the mean brain area was significantly decreased and the mean ventricular space was significantly increased in patients with MD compared with the control subjects. Although we have confirmed brain atrophy in patients with MD in previous reports, a regression analysis indicated that the brain shrinks progressively with age in patients with this disorder and in control subjects, resulting in overlapping values for younger subjects.

CONCLUSION

Magnetic resonance spectroscopy indicates that the cerebral abnormalities in patients with MD may be present at an early stage, when the results of magnetic resonance imaging studies are still equivocal.

Expression of cyclooxygenase-2 in human hepatocellular carcinoma: relevance to tumor dedifferentiation

Cyclooxygenase (COX) is a key enzyme in the synthesis of prostanoids. Two isoforms of this enzyme have been identified: COX-1 and COX-2. Recent studies have suggested that COX-2, but not COX-1, may play a role in colorectal tumorigenesis. In the present study, we investigated the expression of COX-2 as well as COX-1 in human hepatocellular carcinoma (HCC) tissues using immunohistochemistry and immunoblotting. Forty-four surgically resected HCC tissues with adjacent nontumorous livers (NTs), involving 17 cases of chronic viral hepatitis and 27 cases of cirrhosis, and 7 surgically resected, histologically normal liver tissues were used. The well-differentiated HCC expressed COX-2 more frequently and strongly than less-differentiated HCC or hepatocytes of NTs. Less-differentiated HCCs expressed less COX-2 than hepatocytes of NTs, which showed scattered, strong COX-2 expression. Histologically normal liver was weakly positive for COX-2. The expression of COX-1 was weaker than that of COX-2 in hepatic neoplastic and non-neoplastic parenchymal cells. An enhanced expression of COX-1 was not observed in well-differentiated HCCs. Immunoblotting also confirmed up-regulation of COX-2, but not COX-1, in well-differentiated HCCs. The present study is the first to demonstrate a high expression of COX-2 in well-differentiated HCC and a low expression in advanced HCC, in contrast to its continuous expression during colorectal carcinogenesis. These findings suggested that COX-2 may play a role in the early stages of hepatocarcinogenesis, but not in the advanced stages, and may consequently be related to HCC dedifferentiation.

Ex vivo occupancy by tamsulosin of alpha1-adrenoceptors in rat tissues in relation to the plasma concentration

At 0.5-12 h after oral administration of tamsulosin (2.3 micromol/kg) in rats, there was a significant decrease in specific [3H]prazosin binding in the prostate as compared to the control value. The greater decrease occurred in the submaxillary gland. The effect of tamsulosin was mainly due to a marked reduction of [3H]prazosin binding sites (Bmax) rather than to an increase in the dissociation constant (Kd). In contrast, there was only a slight decrease or no change in the [3H]prazosin binding in the spleen, heart, and cerebral cortex of tamsulosin-administered rats at 0.5-12 h. Oral administration of terazosin (21.7 micromol/kg) significantly increased Kd values for [3H]prazosin binding with little effect on Bmax values in the rat prostate at 3 and 6 h. The greater increases in Kd values were observed in the submaxillary gland, spleen and heart at 0.5-12 h. Terazosin had a slight effect on Kd values for the cerebral cortical [3H]prazosin binding. Tamsulosin was absorbed rapidly after oral administration at a dose of 2.3 micromol/kg in rats, and at 6 h, plasma concentration decreased markedly to approximately one-twentieth of the 0.5 h peak level. alpha1-Adrenoceptor occupancy was estimated as a percentage of decrease in Bmax values for [3H]prazosin binding in tissues of tamsulosin-treated rats compared with control rats. The alpha1-adrenoceptor occupancy by tamsulosin in the prostate and submaxillary gland occurred rapidly in parallel with the rise in plasma concentration of tamsulosin, and lasted for over 12 h despite the marked decrease in plasma concentration. Consequently, it is suggested that tamsulosin produces more selective and sustained occupancy in vivo of alpha1-adrenoceptors in the submaxillary gland and prostate of rats than in other tissues.

Hydroxylation and methylthiolation of mono-ortho-substituted polychlorinated biphenyls in rats: identification of metabolites with tissue affinity

The metabolism of three mono-ortho-substituted congeners, 2,3,3',4, 4'-pentachlorobiphenyl (CB105), 2,3',4,4',5-pentachlorobiphenyl (CB118), and 2,3,3',4,4',5-hexachlorobiphenyl (CB156), was investigated with regard to the identification of hydroxy- and sulfur-containing metabolites and their tissue retention in rats. Hydroxylation proceeded primarily at the meta or para position either via an arene oxide, involving NIH shift and dechlorination, or by direct insertion of a hydroxyl group. CB105 was hydroxylated preferably in the 2,3,4-trichlorinated ring to yield 4-OH-2,3,3',4', 5-pentaCB, whereas CB118 was hydroxylated in the 2,4, 5-trichlorinated ring to yield the same hydroxy metabolite to a similar extent. The concentration of 4-OH-2,3,3',4',5-pentaCB in blood was >3 times higher than that in liver, lung, or kidney. The ratios of 4-OH-2,3,3',4',5-pentaCB to unchanged CB in blood were 11:1 for CB105 and 7:1 for CB118. The other two metabolites, 4'-OH-2, 3',4,5,5'-pentaCB from CB118 and 4'-OH-2,3,3',4,5,5'-hexaCB from CB156, also exhibited a high blood affinity. Another metabolism of mono-ortho-PCBs PCBs involved methylthiolation in the vicinal ortho and meta unsubstituted positions to give methylthio metabolites, which were detected as methylsulfonyl metabolites in liver and adipose tissue. The tissue retention of these metabolites might contribute to the toxic and biologic effects of mono-ortho-substituted PCBs.

Reduction of thyroid hormone levels by methylsulfonyl metabolites of polychlorinated biphenyl congeners in rats

Male Sprague-Dawley rats received four consecutive intraperitoneal doses of four kinds of methylsulfonyl (MeSO2) metabolites of polychlorinated biphenyl (PCB) congeners: 3-MeSO2-2,2',3',4',5,6-hexachlorobiphenyl (3-MeSO2-CB132); 3-MeSO2-2,2',3',4', 5,5'-hexachlorobiphenyl (3-MeSO2-CB141); 3-MeSO2-2,2',4',5,5',6-hexachlorobiphenyl (3-MeSO2-CB149) and 4-MeSO2-2,2',4',5,5',6-hexachlorobiphenyl (4-MeSO2-CB149). The congeners were major MeSO2-PCBs determined in human milk, liver and adipose tissue, and the aim was to determine their effect on thyroid hormone levels. All four tested MeSO2 metabolites (20 micromol/kg once daily for 4 days) reduced serum total thyroxine levels by 22-44% at a much lower dose than phenobarbital (PB; 431 micromol/kg once daily for 4 days) on days 2, 3, 4 and 7 after the final doses. Total triiodothyronine levels were reduced 37% by treatment with 4-MeSO2-CB149 at day 7. A 30% increase in thyroid weight was produced by 3-MeSO2-CB141 treatment. Total cytochrome P450 content was increased by 3-MeSO2-CB132, 3-MeSO2-CB141 and 3-MeSO2-CB149, but not by 4-MeSO2-CB149. Thus, it is likely that the 3-MeSO2-hexachlorobiphenyls and 4-MeSO2-CB149 could influence the thyroid hormone metabolism by different mechanism(s). The results show that tested 3- and 4-MeSO2 metabolites of PCB congeners reduce thyroid hormone levels much more than PB in rats. Our finding suggests that the metabolites may act as endocrine-disrupters.

Embryogenesis-promoting factors in rat serum

Regarding whole rat embryo cultures in vitro, rat serum as a culture medium is known to support the normal growth of rat embryos in the organogenesis phase. The purpose of the present study was to isolate the embryogenesis-promoting factors from rat serum as a first step in the development of a defined serum-free medium for a whole embryo culture system. Pooled rat serum after heat inactivation was fractionated into three major peaks (frA, containing a region of void volume, frB, and frC) by gel filtration. The 9.5-day rat embryos that were cultivated for 48 hr in essential salt medium containing frB (with a molecular size range of 100-500 kDa) revealed normal growth. Three proteins (27 kDa, 76 kDa, and 190 kDa) that had the embryogenesis-promoting effects were isolated from 3-hr delayed centrifuged rat serum by the ion exchange chromatography. The 76-kDa protein was found to be rat transferrin by immunoblotting. The 27-kDa protein was identified as apo-AI (the major apoprotein of high-density lipoprotein) by immunoblotting. High-density lipoprotein obtained from pooled rat serum by a NaBr density gradient ultracentrifugation was found to have a positive effect on embryogenesis. The 10-kDa protein was also identified as alpha 1-inhibitor 3 by immunoblotting. In addition, the embryogenesis-promoting effect of the fraction containing 27-kDa and 190-kDa proteins declined within a short period of storage at -20 degrees C. This decrease was countered by supplementing its fraction (D-2) with albumin isolated from rat serum. These results in the present study suggest that transferrin, high-density lipoprotein, and alpha 1-inhibitor 3 in rat serum may be embryogenesis-promoting factors, and that albumin appeared to play a role in the embryogenesis of rat embryos in whole embryo cultures.

Receptor occupancy in myocardium, adrenal cortex, and brain by TH-142177, a novel AT1 receptor antagonist in rats, in relation to its plasma concentration and hypotensive effect

PURPOSE

To study the relationship between angiotensin II (AII) receptor occupancy ex vivo in tissues plasma concentration and hypotensive effect of a novel AII receptor antagonist, TH-142177 and losartan in rats.

METHODS

At 2, 8 and 24 hr after oral administration of TH-142177 and losartan in rats, AII receptors in myocardium, adrenal cortex and cerebral cortex were determined by radioligand binding assay using [125I]Sar1,Ile8-AII. Plasma concentrations of both drugs and metabolite in rats were also measured using validated HPLC assays. Further, systolic blood pressure (SBP) in conscious renal hypertensive rats treated orally with TH-142177 and losartan were measured by using a tail cuff plethysmographic method.

RESULTS

Oral administration of TH-142177 (1.8 and 5.5 micromol/kg) and losartan (6.5 and 21.7 micromol/kg) in rats brought about dose-dependent decreases in [125I]Sar1,Ile8-AII binding sites (Bmax) in myocardium and adrenal cortex. The extent of receptor occupancy by both drugs in adrenal cortex was maximal at 2 hr later but that in myocardium at 8 hr later. Further, the receptor occupancy was more sustained in myocardium than adrenal cortex. The ex vivo binding affinity of TH-142177 for AII receptors in these tissues was roughly three times higher than that of losartan. Also, cerebral cortical [125I]Sar1,Ile8-AII binding was significantly reduced by oral administration of losartan but not by TH-142177. The time course of AII receptor occupancy by both drugs in adrenal cortex appeared to be in parallel with that of their plasma concentrations, while the time course in myocardium correlated with that of their hypotensive effects rather than plasma concentrations.

CONCLUSIONS

TH-142177 produced a relatively selective and sustained occupancy ex vivo of AII receptors in myocardium and adrenal cortex of rats with approximately three times greater potency than losartan. Its time course of myocardial receptor occupancy was in parallel with that of hypotensive effect rather than plasma concentration.

In vivo receptor binding of novel alpha1-adrenoceptor antagonists for treatment of benign prostatic hyperplasia

New types of alpha1-adrenoceptor antagonists (tamsulosin, KMD-3213 and JTH-601) are currently receiving a great deal of attention, especially in terms of developing effective therapeutic agents to treat bladder outlet obstruction with less side effects, such as postural hypotension, in patients with benign prostatic hyperplasia (BPH). In vivo alpha1-adrenoceptor binding properties of these antagonists in prostate and other tissues of rats were examined. Intravenous injections of tamsulosin, KMD-3213 and JTH-601 inhibited dose-dependently in vivo specific [3H]tamsulosin binding in various tissues. Ratios of ID50(aorta) to ID50(prostate) of KMD-3213 and JTH-601 were greater than those of tamsulosin and prazosin. Further, the ratios of ID50(spleen) to ID50(submaxillary gland) of these drugs were greater than that of prazosin. Following intravenous injections of [3H]KMD-3213 in rats, the amount of specific binding in prostate was significantly greater than that of [3H]prazosin, but that in aorta or spleen was much smaller. Interestingly, [3H]JTH-601 showed little in vivo specific binding in aorta. These data suggest that KMD-3213 and JTH-601 exhibit higher affinity to alpha1-adrenoceptors in prostate and submaxillary gland than in vascular tissues in vivo.

[Metastasis of small cell lung cancer to the parotid gland as the initial clinical manifestation, followed by metastases to the pituitary gland and lumber spinal cord]

The patient was a 48-year-old woman. In January 1995, she noted swelling in the left parotid gland, and saw an otorhinolaryngologist. Needle biopsy showed small cell carcinoma, and she was subsequently admitted to our hospital. Chest radiography revealed a tumor shadow in the hilus of the right lung. Bronchial biopsy revealed small cell carcinoma of the lung (T 4 N 3 M 1, stage IV). Chemotherapy, with a CDDP-VP-16 regimen, achieved no response. She later developed bitemporal hemianopsia and abducens nerve palsy. Brain MRI revealed metastasis in the pituitary gland. Chemotherapy and radiotherapy were efficacious for only a few months. She also developed pain and numbness in the left leg, attributable to intramedullary metastasis (L 1/2, L 4/5) shown on MRI. It is extremely rare for a metastasis to the parotid gland to be the initial clinical manifestation of a small cell lung cancer which later develops widespread metastases to the pituitary gland and lumbar spinal cord.

Inhibition of cell-cell communication by methylsulfonyl metabolites of polychlorinated biphenyl congeners in rat liver epithelial IAR 20 cells

The effects of three polychlorinated biphenyl (PCB) congeners and their six methylsulfonyl (MeSO2)-metabolites on cell communication have been investigated in the scrape-loading/dye-transfer assay in IAR 20 rat liver epithelial cells. The results demonstrated that at non-cytotoxic concentrations 2,2',4',5-tetrachlorobiphenyl, 2,2',4',5,5'-pentachlorobiphenyl (2,2',4',5,5'-pentaCB), 2,2',4',5,5',6-hexachlorobiphenyl (2,2',4',5,5', 6-hexaCB), and their 3- and 4-MeSO2 derivatives completely inhibited the cell communication within 1 h. 4-MeSO2-2,2',4',5,5'-pentaCB and 4-MeSO2-2,2',4',5, 5',6-hexaCB appeared to inhibit the cell communication at slightly lower concentration than their parental PCB congeners and 3-MeSO2 derivatives. The results show that 3- and 4-MeSO2 derivatives of the PCB congeners tested inhibit gap junction intercellular communication at about the same potency as their parental compounds. Since inhibition of cell communication is often observed after treatment with many tumor promoters, our findings suggest that the metabolites may also act as tumor promoters.

Brain pharmacokinetics and in vivo receptor binding of 1,4-dihydropyridine calcium channel antagonists

Brain pharmacokinetics of 1,4-dihydropyridine (DHP) calcium channel antagonists and their in vivo receptor binding in mice were characterized. The area under the concentration vs time curve (AUCbrain) for [3H]nifedipine, [3H]nimodipine and [3H]PN 200-110 in mouse brain after intravenous injection was higher than that for [3H]amlodipine. Brain/plasma concentration ratios (AUCbrain/AUCplasm) for [3H]nimodipine and [3H]PN 200-110 were 3 to 5 times higher than those for [ H]nifedipine and [3H]amlodipine. Further, brain/heart concentration ratios (AUCbrain/AUCheart) for [3H]nifedipine, [3H]nimodipine and [3H]PN 200-110 were about 20 times higher than the ratio for [3H]amlodipine. A significant amount of specific binding in particulate fractions of mouse brain was detected in vivo by intravenous injection of [3H]nifedipine, [3H]nimodipine and [3H]PN 200-110 but not [3H]amlodipine. These data suggest that [3H]nifedipine, [3H]nimodipine and [3H]PN 200-110 are more extensively taken up into brain from plasma than [3H]amlodipine and bind to the receptor sites in brain parenchymal cells in a significant amount in vivo. In conclusion, the present simultaneous measurement of pharmacokinetics and in vivo receptor binding in mouse brain suggests an usefulness of calcium channel antagonists such as nimodipine in the pharmacotherapy of brain diseases.