[Subcellular distribution of porphyrins and anti-lipid peroxidative effect in protoporphyrin-administered rat liver]

The distribution and the anti-lipid peroxidative effects of porphyrins in the hepatic subcellular fractions in rats were studied after intravenous administration of protoporphyrin (PP). PP and/or PP-derived porphyrins were mainly distributed in the membrane-containing fractions of 600 x g-, 10,000 x g- and 100,000 x g-sediment from the liver homogenates of rats receiving a 20 mg/kg dose of PP. The lipid peroxidation induced by L-ascorbic acid in the fractions of 600 x g-, 10,000 x g- and 100,000 x g-sediment from the PP-treated rats was suppressed during 1-168 h, 1-168 h and 12-168 h, respectively, after the PP treatment. The suppression of the peroxidation in the liver mitochondria from the PP-treated rats was further enhanced by the addition of the hepatic cytosol from the PP-treated rats. The extent of the suppression by the addition of the cytosol from the PP-treated rats at 24 h after the PP administration was greater than those at 0 and 168 h after the PP administration. These results indicate that PP and/or PP-derived porphyrins distributed in the liver still exert antioxidative actions and that there might exist some unknown factors enhancing the actions in the hepatic cytosol.

Identification of biliary metabolites of m-dichlorobenzene in rats

At least 12 metabolites were observed in the bile of rats administered with m-dichlorobenzene in the preliminary experiments by HPLC. Some of them were assumed to be conjugates containing phenyl and dihydro-hydroxyphenyl moieties with glutathione or cysteine by enzymatic and thermal reactions. To isolate these metabolites, the bile collected from 20 rats administered with 500 mg/kg of m-dichlorobenzene and 300 mg/kg of cysteine was separated into five fractions by HPLC. Eighteen metabolites were isolated from these fractions by TLC and HPLC. The chemical structure of the major metabolite excreted was determined as trans-2,4-dichloro-6-(glutathion-S-yl)cyclohexa-2,4-dien+ ++-1-ol by 13C-NMR, 1H-NMR, FAB-MS, and some reaction experiments. The metabolite excreted in the secondary largest amount was identified as its positional isomer, trans-3,5-dichloro-6-(glutathion-S-yl)cyclohexa-2,4-dien+ ++-1-ol. Their diastereomers were also observed in the bile. trans-2,4-Dichloro-6-(cystein-S-yl)cyclohexa-2,4-dien- 1-ol and its positional isomer, which were possibly derived from glutathione conjugates above, were also identified. 3,5-Dichlorophenyl conjugates with glutathione or cysteine and 3,5-dichlorophenyl mercapturic acid, and their 2,4-dichlorophenyl isomers, were excreted. Three monochlorophenol conjugates, of which chemical structures were still not established, were present in the bile.

Binding characteristics of naftopidil and α1-adrenoceptor antagonists to prostatic α-adrenoceptors in benign prostatic hypertrophy

Binding properties of naftopidil and alpha 1-adrenoceptor antagonists to alpha-adrenoceptors in prostates from benign prostatic hypertrophy (BPH) were characterized by radioreceptor assays using [3H]prazosin and [3H]rauwolscine. Specific binding of [3H]prazosin and [3H]rauwolscine in human prostatic membranes was saturable and of high affinity, and it showed a pharmacological specificity which characterized alpha 1 and alpha 2-adrenoceptors, respectively. Naftopidil and several alpha 1 antagonists competed for prostatic [3H]prazosin binding in order: R-(-)-YM-12617 greater than prazosin greater than bunazosin greater than terazosin greater than naftopidil greater than urapidil, and the inhibitory effect (Ki = 11.6 nM) of naftopidil was 10 to 45 times less potent than quinazoline derivatives such as prazosin, bunazosin and terazosin. The potencies of these antagonists in competing for [3H]prazosin binding sites in human prostates correlated well with their pharmacological potencies (pA2). Scatchard analysis indicated that the decrease of prostatic [3H]prazosin binding by naftopidil was due to a marked increase in the Kd value without a change in the Bmax value. The inhibition of prostatic [3H]prazosin binding by naftopidil was reversible. Naftopidil also inhibited prostatic [3H]rauwolscine binding (Ki = 70.0 nM). Thus, it is suggested that naftopidil antagonizes alpha 1-adrenoceptors in human prostates in a competitive and reversible manner.

Nasal absorption of digoxin in rats

The nasal administration of digoxin was studied in rats and compared to intravenous, intraduodenal and rectal administration of the drug. The results indicated that the plasma level of digoxin after nasal administration was comparable to the level after intravenous injection. Administration by the intraduodenal and rectal routes resulted in considerably lower plasma levels. These data reveal that digoxin absorption across the nasal membranes is a reasonable approach. In the in situ nasal and intestinal perfusion experiments, digoxin disappeared from the perfusate following the apparent first-order kinetics. The nasal and intestinal absorption rate of digoxin was reduced by an increase in the perfusion volume. The plot of absorption rate constant against 1/volume resulted in a straight line, suggesting that digoxin is absorbed from nasal mucosa by a passive diffusion process.

[3H]bunazosin, a novel selective radioligand of alpha 1 adrenoceptors in human prostates

The binding properties of a new radioligand, [3H]bunazosin, were studied in membranes of human prostates with benign prostatic hypertrophy (BPH). Specific binding of [3H]bunazosin was saturable, reversible, and of high affinity (Kd = 0.55 +/- 0.04 nM). The density of [3H]bunazosin binding sites (Bmax) was 676 +/- 33 fmol/mg. protein. [3H]Bunazosin rapidly associated with its binding sites in membranes of human prostates and reached steady state by 20 min. at 25C. The rate constants for association and dissociation of [3H]bunazosin binding were calculated to be 0.11 +/- 0.01/nM/min. and 0.05 +/- 0.02/min. (n = 4), respectively. Seven alpha 1 adrenoceptor antagonists competed with [3H]bunazosin for the binding sites in the rank order: R-(-)-YM-12617 greater than prazosin greater than SGB-1534 greater than bunazosin greater than terazosin greater than naftopidil greater than urapidil. In parallel studies with [3H]bunazosin, the Kd and Bmax values for [3H]prazosin binding in human prostates were slightly lower. There was a similarity in the potency and rank order of seven alpha 1, adrenoceptor antagonists for the inhibition of [3H] bunazosin and [3H]prazosin binding in human prostates. The new [3H]bunazosin binding assay in human prostates is remarkable for its low degree of nonspecific binding as compared to [3H]prazosin, especially at high ligand concentrations. Thus, [3H]bunazosin may become a useful radioligand for the further analysis of the alph 1 adrenoceptor binding sites in human prostates.

Japan's dilemma with the definition of death

Japan is unusual among industrialized countries in its reluctance to use brain criteria to determine death and harvest transplant organs. This results from public distrust of the medical profession due to an earlier incident, and from concern that technological interventions will threaten religious and cultural traditions surrounding death and dying. Public acceptance is growing, however, as medical professional groups and universities develop brain criteria, and as pressure from patients who could benefit from a transplant, as well as from foreign countries, increases.

Mechanisms of absorption of inorganic mercury from rat small intestine. IV: Effect of chelating agents and cysteine on absorption of mercuric chloride in situ and in vitro

The effects of chelating agents (citric acid, tartaric acid, penicillamine and ethylenediaminetetraacetic acid) and cysteine on the absorption of HgCl2 were investigated in rats. Perfusion of the small intestine showed that the chelating agents and cysteine decreased the absorption of HgCl2 depending on their stability of constants with Hg2+, under the predominant conditions of water absorption and secretion. The difference in absorption of HgCl2 between both conditions was inversely correlated with their logarithmic stability constant values. These agents decreased the transport of HgCl2 through the everted intestinal wall and the uptake of HgCl2 by the intestinal brush border membrane in a similar manner. From these results, it is suggested that the chelating agents and cysteine decrease the absorption of HgCl2 through the pores of the brush border membrane due to the solvent drag effect.

Relationship between nasal absorption and physicochemical properties of quaternary ammonium compounds

The present study was undertaken to investigate the in situ nasal absorption of a series of tetraethylammonium chloride-related aliphatic quaternary ammonium compounds in rats and its relationship with their physicochemical properties (molecular weight and partition coefficient). All of the ten quaternary ammonium compounds examined were found to be absorbed through the nasal mucosa of rats. The nasal absorption rates of ethyltrimethyl-ammonium iodide and tetraethylammonium chloride, with the lowest molecular weight, were the highest, and those of tetra-n-butylammonium chloride and tetra-n-propylammonium bromide, with high molecular weight, were much lower. Thus, there was a tendency that the nasal absorption rates of quaternary ammonium compounds in rats decreased with an increase in their molecular weight. A physicochemical study has shown that there was a linear relationship between the molecular weight of the ten quaternary ammonium compounds and their partition coefficient, thereby suggesting an increase in lipophilicity with the molecular weight. In addition, there was a good correlation between the extent of the nasal absorption of the quaternary ammonium compounds studied and their molecular weight or partition coefficient. These data suggest that there is a reciprocal relationship between the membrane transport of quaternary ammonium compounds in the nasal mucosa and their lipophilic character. In conclusion, it seems likely that quaternary ammonium compounds are predominantly absorbed from the nasal mucosa of the rat through waterfilled channels or pores rather than through the lipid membrane.

Giant middle cerebral artery aneurysm with parent artery occlusion--case report

A 54-year-old female was admitted with consciousness disturbance and right hemiparesis. Computed tomographic (CT) scans and angiograms revealed diffuse subarachnoid hemorrhage, a partially thrombosed, giant middle cerebral artery aneurysm (5 x 5 x 4 cm), and occlusion of the parent artery at the aneurysm site. Despite conservative treatment, a generalized convulsion occurred. Emergency CT scans revealed irregular enlargement of the left temporal high-density mass and severe mass effect due to cerebral infarction. Barbiturate coma therapy was administered, but she did not recover and died 9 days after admission. Only two cases of ruptured aneurysm with simultaneous occlusion of the major cerebral vessels have been reported, both with poor outcome. In this case, the mechanism of parent artery occlusion is unclear, but thrombus protrusion from the giant aneurysm into the parent artery may have been involved.

Antioxidative effect of protoporphyrin on lipid peroxidation in tissue homogenates of intravenously administered rats

Effect of intravenous administration of protoporphyrin IX (PP) on lipid peroxidation was studied in rats. PP and/or PP-derived porphyrins were found to be mainly distributed in livers, spleen and lungs. Dose-dependent decreases in the Fe2+ and L-ascorbic acid-stimulated lipid peroxidation in homogenates of livers and dose-dependent increases in porphyrin concentration in livers were observed after the PP injection. In the experiments with a 20 mg/kg dose of PP, the peroxidation level in the liver homogenates reached its minimum level during the period of 3 to 24 h accompanying the high porphyrin concentration in livers after the administration. After 96 h, a relatively high porphyrin concentration was still retained, but decreases in the peroxidation levels had ceased. PP administration caused a dose-dependent decrease in the endogenous lipid peroxides in livers within 0.5 h and the low levels were maintained throughout the course of the 168-h study. These results clearly show that the administered PP is distributed in the liver and inhibits the lipid peroxidation in vivo.

Difference in effect of sodium selenite on mercury distributions after duodenal administration of mercuric chloride and mercuric oxide

To obtain evidence for difference in the absorptive forms of HgCl2 and HgO from duodenum, the Hg distributions after the duodenal administration of HgCl2 and HgO and the effect of Na2SeO3 on their Hg distributions were compared. The Hg concentrations in erythrocytes and liver 2 hr after the administration of HgCl2 were significantly lower and higher than those of HgO, respectively, but their Hg distributions at 3.5 or 5 hr became identical. The administration of Na2SeO3 (intravenously) 2 hr after the administration of HgCl2 and HgO resulted in significant differences in their Hg concentrations in plasma, erythrocytes and kidney at 3.5 or 5 hr. These results suggest that the absorptive form of HgCl2 from the duodenum differs from that of HgO and this difference is a cause for the marked difference in effect of Na2SeO3 on the Hg distributions of HgCl2 and HgO.

The effect of oral metyrapone on aqueous humor dynamics in normal human eyes

We studied the possible influence of oral metyrapone tartrate (which inhibits the adrenal biosynthesis of cortisol) on the rate of aqueous humor flow in 9 eyes of 8 normal subjects by fluorophotometry. On the control day, the mean value of Ko was 1.04 +/- 0.32 min-1 x 10(-2), where Ko was the loss coefficient from the anterior chamber. On the metyrapone trial day, the mean value of Ko was 0.63 +/- 0.15 min-1 x 10(-2). The mean difference in Ko between the two periods was significant (P less than 0.005). These results indicated that systemic metyrapone administration decreases the rate of aqueous humor flow.

Administration of a synthetic antiprotease reduces smoke-induced lung injury

Our previous studies suggest that a neutrophil-mediated inflammatory injury causes a major fraction of the pulmonary edema that occurs after smoke inhalation. Because activated neutrophils extrude cytotoxic proteases, the current study was conducted to evaluate the role of proteases in the pulmonary microvascular injury. Twelve sheep, instrumented for collection of lung lymph, were insufflated with cotton smoke. The sheep were treated 30 min after smoke inhalation with either gabexate mesilate (an inhibitor of serine proteases) or vehicle. Smoke inhalation resulted in an increased protease activity in the lung interstitium, as evidenced by decreases in both antiprotease activity and immunoreactive alpha 2-macroglobulin. Intravenous infusion of gabexate mesilate prevented the decrease in antiprotease activity. The protease inhibitor significantly attenuated the smoke-induced increase in transvascular fluid and protein flux, with untreated animals exhibiting 460% increases in flux compared with 180% in the inhibitor treated sheep. The protease inhibitor also eliminated the functional degradation in gas exchange that was observed in the untreated sheep. These studies strongly suggest that an increase in pulmonary proteolytic enzyme activity is responsible for a significant fraction of the degradation in microvascular integrity and gas exchange that is associated with smoke inhalation injury.

Effects of sulfur-containing metabolites of hexachlorobenzene on the heme metabolic enzymes in rat liver

Effects of hexachlorobenzene (HCB) and its sulfur-containing metabolites on the heme metabolic enzymes in rat liver were investigated. A single injection of HCB caused the increase in activities of delta-aminolevulinic acid (ALA) synthetase and heme oxygenase, and contents of cytochrome P-450 and total heme. After a single injection of pentachlorothioanisol (PCTA) or pentachlorophenyl methyl sulfore (PCPSO2Me), ALA synthetase activity was enhanced. Heme oxygenase activity was increased by PCPSO2Me treatment. Cytochrome P-450 and total heme contents were increased by PCPSO2Me or 1,4-bis(methylthio)tetrachlorobenzene (MTTCB). When HCB was injected once daily for 5 weeks, a marked increase in ALA synthetase activity, a significant decrease in ALA dehydratase, almost complete inhibition of uroporphyrinogen decarboxylase activity, and an increased excretion of total porphyrin in the urine were shown. After chronic treatment with its sulfur-containing compounds, PCPSO2Me and MTTCB produced a significant increase in ALA synthetase activity. However, activities of ALA dehydratase and uroporphyrinogen decarboxylase, and excretion of total porphyrin in the urine were unaltered. At this time, the concentrations of the corresponding sulfur-containing compound and related metabolite(s) in blood, liver and kidney were nearly the same as those observed in HCB-treated rats. It is suggested that PCPSO2Me and MTTCB could induce the hepatic ALA synthetase, but, these metabolites, and also PCTA, were not able to induce the porphyria in female rats, and the induction of porphyria by HCB is not attributable to the action of its sulfur-containing compound.

Mechanisms of absorption of inorganic mercury from rat small intestine. III. Comparative absorption studies of inorganic mercuric compounds in vitro

The transport of various inorganic mercuric compounds (HgX2s) was compared in everted intestinal sacs and intestinal brush border membrane vesicles (BBMV) of the rat. The preparations were incubated in a medium containing 10(-4) M HgX2 at pH 5.5, 6.4 or 7.4, respectively. The order of transport through the intestinal wall at each pH (HgOAc)2 greater than HgCl2 greater than Hg(SCN)2 greater than HgBr2 greater than Hg(CN)2) was the reverse order of their stability constants, and an increase in pH tended to increase the transport of HgX2. In the experiment with BBMV, similar results were obtained except for the transport of Hg(CN)2. These results suggest that the extent of transport of a certain HgX2 depends on its stability constant, and that the increase in pH promotes the transport possibly as a result of the conversion of HgX2 to Hg(OH)X and Hg(OH)2.

[Ruptured cerebral aneurysm followed by primary intracranial malignant lymphoma: case report]

Reported herein is a case of ruptured anterior cerebral aneurysm followed by primary intracranial malignant lymphoma. A 73-year-old female was admitted to our hospital on October 20, 1986, with a severe subarachnoid hemorrhage. Microsurgery was performed immediately on the day of admission because cerebral angiography revealed bilateral distal anterior cerebral artery aneurysms. Consciousness gradually deteriorated due to cerebral vasospasm from the 3rd day following surgery. To protect the brain, corticosteroid (methylprednisolone 1500 mg, dexamethasone 252 mg) was administered for 26 days after surgery. In spite of treatment, in March 1987 neurological examination revealed akinetic mutism, but CT scan did not reveal any evidence of tumor. CT scan performed on May 2, 1987, revealed a mass lesion in the left frontotemporal lobes and left basal ganglia. Histological diagnosis of malignant lymphoma (diffuse, large-cell type) was obtained by stereotactic biopsy. Radiotherapy (41 Gy of 60Co) was carried out. The CT scan performed on August 26, 1987 revealed that the abnormal enhanced lesion had disappeared. However, neurological findings had not remarkably improved. The patient died of renal failure in February 1988, but tumor recurrence had not been noted in CT scans. Autopsy could not be performed. Whole body CT scan and 67Gd scintigram did not reveal any other tumors except in the brain. Ruptured cerebral aneurysm followed by primary intracranial malignant lymphoma is very rarely reported. In such cases, which have unusual clinical courses and CT findings, we recommend stereotactic biopsy to treat this kind of radiosensitive tumor. The connection between malignant lymphoma and immunosuppression has been considered.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium channel receptor sites for (+)-[3H]PN 200-110 in coronary artery

The receptor sites for 1,4-dihydropyridine (DHP) Ca++ channel antagonists in porcine coronary artery were identified and characterized by a binding assay using (+)-[3H]PN 200-110 as a radioligand. Specific (+)-[3H]PN 200-110 binding in porcine coronary artery was saturable, reversible and of high affinity (Kd = 0.24 nM) and it showed a pharmacological specificity as well as stereoselectivity which characterized the receptor sites for DHP Ca++ channel antagonists. DHP antagonists competed for the (+)-[3H]PN 200-110 binding in order: PN 200-110 greater than mepirodipine greater than nisoldipine greater than nicardipine greater than nitrendipine greater than nimodipine greater than nifedipine greater than (-)-PN 200-110. (+)-PN 200-110 was approximately 140 times as potent as the (-)-isomer. The potencies (PKi) of these eight DHP Ca++ channel antagonists in competing for (+)-[3H]PN 200-110 binding sites in porcine coronary artery correlated well with their pharmacological potencies. Specific (+)-[3H]PN 200-110 binding in the coronary artery was enhanced by d-cis-diltiazem and was inhibited incompletely by verapamil and D-600. In EDTA-pretreated coronary artery, the maximal number of binding sites for specific (+)-[3H]PN 200-110 binding was reduced (80%) markedly, and it was restored to the untreated level by the addition of Ca++ and Mg++.(ABSTRACT TRUNCATED AT 250 WORDS)

Antioxidative effect of several porphyrins on lipid peroxidation in rat liver homogenates

The effect of several porphyrins on Fe2(+)-ascorbic acid-stimulated lipid peroxidation was examined in rat liver homogenates. Not only protoporphyrin IX (PP) but also mesoporphyrin IX and hematoporphyrin inhibited the lipid peroxidation. Some porphyrins, in which 6- and 7-carboxyethyl groups were esterified with a methyl group, such as protoporphyrin IX dimethyl ester and mesoporphyrin IX dimethyl ester, had no antioxidative effect. Hemin and zinc protoporphyrin IX, which are metal-chelated porphyrins, inhibited the lipid peroxidation while cobalt protoporphyrin IX and tin protoporphyrin IX showed no antioxidative effect. Thus, some of the porphyrins used in the present study showed an antioxidative effect as did PP, but the others did not show such an effect.

Nasal absorption of tetraethylammonium in rats

The in vivo and in situ nasal absorption of tetraethylammonium in rats was studied. Following nasal administration of tetraethylammonium (150 mumol/kg) to rats, there was a rapid increase in plasma concentration of tetraethylammonium followed by a slow increase. The absolute bioavailability of nasal tetraethylammonium administration was 79%. In rats, tetraethylammonium was shown to be more efficiently absorbed from nasal mucosa than from intestine. In in situ nasal perfusion experiments, the nasal absorption rate of tetraethylammonium was reduced by an increase in perfusion volume. The plot of absorption rate constant against 1/volume did not result in a straight line. In addition, there was a concentration-dependent decline in the absorption rate of tetraethylammonium with an increase in its initial concentration in the perfusion solution. Choline and 2,4-dinitrophenol significantly inhibited the nasal absorption of tetraethylammonium. These data may suggest the existence of a carrier-mediated transport process of tetraethylammonium in nasal mucosa of rats.

Factors involved in absorption of organic mercuric compounds from rat small intestine: comparative study with mercuric chloride in situ

A correlation between absorption of organic mercuric compounds and their molecular weight or lipophilicity was investigated by the perfusion of rat small intestine. The intestine was perfused for 1.0 hr at different osmolarity and different pH with buffers containing 10(-4) M organic mercuric compounds, methyl mercuric chloride (MMC), phenyl mercuric chloride (PMC), p-chloromercuribenzoic acid (PCMB) and p-chloromercuriphenylsulfonic acid (PCMBS). The order of absorption of these compounds at several osmolarities and pHs (MMC greater than PMC greater than PCMB greater than PCMBS) was inversely correlated to their molecular weight. The increase in pH decreased markedly the absorption and n-octanol/water partition coefficient of PCMB, and it decreased scarcely those of MMC, PMC and PCMBS. The order of the coefficients at each pH was as follows; PMC greater than MMC greater than PCMB greater than PCMBS, in disagreement with the order of absorption. These results suggest that the molecular weight is more important factor in the intestinal absorption of organic mercuric compounds than the lipophilicity.

Ethics committees for "high tech" innovations in Japan

Although ethics committees in Japan have been developing in major medical schools and in some hospitals, their members are usually medical professionals from the same institution. The lack of national legislation for setting up ethics committees permits only a voluntary code of standards for doing clinical research work in high tech medical applications. The author argues for the necessity of more open debate on bioethical issues and proposes the participation of the lay public and bioethicists in Ethics Committee in Japan.

[Prognosis in chronic pulmonary disease and cor pulmonale]

Echocardiography and cardiac catheterization were performed in 30 patients of chronic pulmonary disease and cor pulmonale. We studied the relation of echo-cardiographic data and pulmonary hemodynamics to prognosis in these patients. In the nonsurvival group (12 patients) the extent of dyspnea was worse significantly (p less than 0.05), PaO2 was decreased significantly (p less than 0.05, 7 +/- 8.2 Torr), right ventricular preejection period (RPEP)/right ventricular ejection time (RVET) ratio increased significantly (p less than 0.05, 0.51 +/- 0.07), left ventricular diastolic diameter index (LVDdI) was shortened significantly (p less than 0.05, 23.5 +/- 3.1 mm/m2), and pulmonary capillary wedge mean pressure (PCWm) rose significantly (p less than 0.05, 11.9 +/- 6.9 mmHg) in comparison with the survival group (12 patients). In the survival group PaO2, RPEP/RVET ratio, LVDdI and PCWm averaged 60.9 +/- 12.8 Torr, 0.41 +/- 0.09, 27.5 +/- 5.1 mm/m2, 6.2 +/- 3.3 mmHg, respectively. The rate of survival was decreased significantly (p less than 0.05) in pulmonary vascular resistance (PVR) of greater than 400 dyne.sec.cm-1 or stroke volume index (SVI) of less than 35 ml/m2. These factors and 3 factors of obesity, %VC and pulmonary artery mean pressure (PAPm) differentiated nonsurvivors from survivors with linear discriminant function.

Contribution of methylsulfonyl metabolites of m-dichlorobenzene to the heme metabolic enzyme induction by the parent compound in rat liver

In the present study, we investigated the contribution of methylsulfonyl metabolites derived from m-dichlorobenzene (m-DCB) on the heme metabolic enzyme induction by the parent compound in rats. The time courses of the effects of a single ip administration of m-DCB (200 mg/kg, 1.36 mmol/kg) and 2,4- and 3,5-dichlorophenyl methyl sulfones (2,4- and 3,5-DCPSO2Mes) (each 50 mumol/kg) on hepatic microsomal cytochrome P450 content were almost in parallel with those on the total heme content in liver microsomes. m-DCB significantly increased the heme oxygenase activity, but 2,4- and 3,5-DCPSO2Mes did not. On the other hand, m-DCB and both methyl sulfones markedly enhanced the delta-aminolevulinic acid (ALA) synthetase activity. No change was observed in percentage saturation of the tryptophan pyrrolase activity after administration of m-DCB, whereas this ratio at 6 hr after injection of 3,5-DCPSO2Me was increased. In the liver of the DL-buthionine-(S,R)-sulfoximine (BSO)-treated rats dosed with m-DCB, both of 2,4- and 3,5-DCPSO2Mes were present at significantly lower concentrations than in non-BSO-treated rats. Additionally, the m-DCB did not elevate the ALA synthetase activity in the BSO-treated rat. On the other hand, the administration of either 2,4- or 3,5-DCPSO2Mes to BSO-treated rats resulted in induction of ALA synthetase. m-DCB and 2,4- and 3,5-DCPSO2Mes produced a dose-related increase in liver levels of methyl sulfones. The changes in the ALA synthetase activity after the administration of varying doses of m-DCB were similar to those after the administration of 2,4- or 3,5-DCPSO2Mes, whereas the sum of the concentration of two methyl sulfones in the liver of rats dosed with m-DCB was almost the same as the concentration of methyl sulfone after the administration of either 2,4- or 3,5-DCPSO2Mes. The results strongly suggest that the methyl sulfones derived from m-DCB, i.e., 2,4- and 3,5-DCPSO2Mes, contribute highly to the induction of the ALA synthetase activity by the parent compound.