Purification and characterization of hepatic steroid hydroxylases from untreated rainbow trout

Induction of hepatic CYP1A by indole-3-carbinol in protection against aflatoxin B1 hepatocarcinogenesis in rainbow trout

This study examined the significance of hepatic cytochrome P4501A (CYP1A) induction in the inhibition of aflatoxin B1 (AFB1)-DNA adduction by indole-3-carbinol (I3C) in rainbow trout. I3C, fed prior to [3H]AFB1 exposure, provided dose-dependent inhibition of hepatic AFB1-DNA binding, which appeared to vary inversely with hepatic CYP1A-mediated ethoxyresorufin O-deethylase (EROD) activity (r = -0.81, P = 0.051). However, 1000 ppm dietary 13C inhibited AFB1-DNA adduction without detectably inducing CYP1A protein or EROD activity. Dietary I3C was found to inhibit AFB1-DNA adduction by approximately 50%, whether [3H]AFB1 was injected ip 1, 2, 3, 5 or 7 days after the onset of I3C feeding, yet hepatic EROD activity was only transiently induced over this period and was not correlated with AFB1-DNA inhibition. Microsome-catalysed AFB1-DNA binding in vitro did correlate inversely with EROD activity in microsomes from control- and I3C-treated trout (r = -0.955, P = 0.01), but data obtained using microsomes from beta-naphthoflavone-treated trout suggest that this observation may not be indicative of a cause-and-effect relationship. I3C-mediated reduction in covalent binding was not due to I3C derivatives in the microsomal preparation or to reduced CYP protein levels, but may reflect a lower microsomal catalytic capacity for AFB1 epoxidation as a result of enzyme inactivation. In addition, the major I3C derivative found in liver, 3,3'-diindolylmethane, has been shown to be a non-competitive inhibitor of EROD, and of enzymes that catalyse AFB1 epoxidation. These findings indicate little, if any, role for CYP1A induction in the inhibition of AFB1 carcinogenicity in rainbow trout by levels of I3C likely to be encountered in cruciferous vegetables.

Influence of growth hormone on the hepatic mixed function oxidase and transferase systems of rainbow trout

The effect of GH treatment on hepatic cytochrome P450 content, aryl hydrocarbon hydroxylase (AHH), aminopyrine-N-demethylase (AND), testosterone hydroxylase, testosterone 5α- and 5β-reductase, UDP-glucuronyl transferase (UDPGT) and glutathione S-transferase (GST) activities in immature rainbow trout were investigated. Hepatic cytochrome P450 content, AHH and GST activities were measured in both GH implanted and GH injected animals whereas other activities were assayed in GH implanted trout only.GH implants significantly decreased cytochrome P450 content at 15 days compared to the control but no significant effect was observed at 15 or 30 d when GH was injected biweekly. In both cases, AHH activity was significantly decreased by GH treatment compared to the control whereas GST remained unchanged. Compared to the control, GH implanted fish exhibited a pronounced inhibition of AND, a decreased 6β and 16β-testosterone hydroxylation, an inhibition of UDPGT with testosterone as substrate and an enhanced 17β-testosterone oxidation.

Inhibition of in vitro aflatoxin B1-DNA binding in rainbow trout by CYP1A inhibitors: alpha-naphthoflavone, beta-naphthoflavone and trout CYP1A1 peptide antibody

Rainbow trout cytochrome P450 (CYP)1A detoxifies aflatoxin B1 (AFB1) to aflatoxin M1 (AFM1), whereas CYP2K1 activates AFB1 to AFB1-8,9-epoxide. We report that alpha-naphthoflavone (ANF) and beta-naphthoflavone (BNF) both strongly inhibit CYP1A-mediated ethoxyresorufin O-deethylase (EROD) activity (Ki = 9.1 +/- 0.8 and 7.6 +/- 1.1 nM, respectively). These inhibitors (selective for mammalian CYP1A at low concentrations), as well as rabbit polyclonal antibody to a trout CYP1A1 peptide (residues 277-294), also strongly inhibited trout microsome-catalyzed AFB1-DNA binding and lauric acid (omega-1) hydroxylation in vitro, reactions previously established to be CYP2K1-dependent. ANF at 0.5, 5, 50 and 500 microM inhibited liver microsome-catalyzed AFB1-DNA binding by 22, 58, 84 and 91%, respectively, whereas BNF at the same concentrations inhibited 22, 74, 78 and 81%, respectively. The CYP1A1 peptide and CYP2K1 polyclonal antibodies (10 mg IgG/mg microsomal protein) inhibited AFB1-DNA binding by 84 and 66%, respectively, compared with pre-immune IgG. Lauric acid (omega-1) hydroxylation was inhibited 61% by 5 microM ANF, 69% by 5 microM BNF and 100% by either antibody at 12 mg IgG/mg microsomal protein. These results demonstrate that mammalian CYP1A inhibitors also inhibit trout microsomal AFB1-DNA binding and lauric acid (omega-1) hydroxylation, catalyzed primarily by CYP2K1. In the absence of evidence that trout CYP1A can catalyze AFB1-DNA binding, the results suggest configuration similarities at, or near, the active sites for these two fish enzymes that result in antibody crossreaction and loss of the inhibitor specificity observed with mammalian CYP1A.

Biotransformation enzyme activities in the olfactory organ of rainbow trout (Oncorhynchus mykiss). Immunocytochemical localization of cytochrome P4501A1 and its induction by β-naphthoflavone

Olfaction is a crucial function in most fish species, but little is known about biotransformation enzymes in the olfactory organ. This study demonstrates that biotransformation enzymes usually found in the rainbow trout liver, are present in the olfactory organ as well. While microsomal cytochrome P450 reductase, p-nitrophenol hydroxylase and cytosolic glutathioneS-transferase presented similar levels in both the olfactory organ and the liver, microsomal 7-ethoxyresorufinO-deethylase (EROD), 7-ethoxycoumarinO-deethylase, and 7-pentoxyresorufinO-deethylase were much lower in the olfactory organ (77-, 35-, 200-times respectively). Furthermore, microsomes from the olfactory organ were able to perform testosterone hydroxylation only in the 16α-position while testosterone was hydroxylated in the 16β-position by liver microsomes. Using polyclonal antibodies raised against perch cytochrome P4501A1, the immunoreactive protein was shown to be strongly expressed in various cellular types forming the nonsensory epithelium. Some immunostaining was also reported in the nonsensory cellular elements constituting the sensory epithelium, while olfactory receptor cells failed to show cytochrome P4501A1-immunoreactivity. Finally, the exposure of rainbow trout to waterborne β-naphthoflavone (0.1 μg ml(-1)) for 2 or 4 days resulted in a higher induction of EROD activity in the olfactory organ compared to the liver. The presence of biotransformation enzymes in the olfactory organ of rainbow trout addresses the question of their involvement in the detoxication/toxication of pollutants as well as in the olfactory function.

Induction of zebrafish (Brachydanio rerio) P450 in vivo and in cell culture

1. Induction of zebrafish P450 by 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) was studied in liver tissue, primary liver cell culture and multipassage cell culture derived from zebrafish haploid and diploid embryos and liver. 2. TCDD induced two hepatic proteins (54 and 50 kDa) in vivo which were recognized by anti-trout P4501A1 IgG. The 54-kDa protein was induced by TCDD in primary and multipassage hepatocyte cultures and in haploid and diploid embryo-derived cells. The proteins in liver homogenates were not induced by aqueous exposure of zebrafish to beta-naphthoflavone (BNF). 3. Homogenates of zebrafish liver, cultured hepatocytes and embryo-derived cells also exhibited increased ethoxyresorufin O-deethylase (EROD) and 7-12-dimethyl-benz[a]anthracene (DMBA) hydroxylase activity following TCDD exposure.

Use of 7-alkoxyphenoxazones, 7-alkoxycoumarins and 7-alkoxyquinolines as fluorescent substrates for rainbow trout hepatic microsomes after treatment with various inducers

Various fluorescent substrates have been used as specific indicators of induction or activity of different cytochrome P450 isozymes in both fish and mammalian species. In an attempt to identify additional definitive fluorescent substrates for use in fish, we examined a series of 7-alkoxyphenoxazones, 7-alkoxycoumarins and 7-alkoxyquinolines as substrates in O-dealkylation assays with hepatic microsomes from rainbow trout (Oncorhynchus mykiss). Microsomes were prepared after 48 hr of treatment with beta-naphthoflavone (beta-NF), pregnenolone-16 alpha-carbonitrile (PCN), phenobarbital (PB), isosafrole (ISF), or dexamethasone (DEX). Total P450 spectra were obtained, and spectral binding studies were performed. Microsomal O-dealkylation rates were greater after ISF treatment than after beta-NF treatment for 7-methoxy-, 7-ethoxy-, 7-propoxy- and 7-benzyloxyphenoxazones but not for 7-butoxyphenoxazone. DEX treatment resulted in a significant elevation of pentoxyphenoxazone metabolism (about a 144-fold increase) compared with microsomes induced by beta-NF (11-fold) and ISF (37-fold). The rates of dealkylation of the alkoxyphenoxazones by ISF-treated microsomes occurred in the following order: methoxy > ethoxy > propoxy > benzxyloxy > butoxy > pentoxy. When beta-NF-treated microsomes were used, the 7-alkoxyphenoxazones were metabolized as follows: methoxy > ethoxy > propoxy > butoxy > benzyloxy = pentoxy, while the order of metabolism of the 7-alkoxycoumarins was: ethoxy >> butoxy > propoxy = methoxy > benzyloxy > pentoxy. None of the other treatments significantly increased the rate of metabolism of any of the alkoxycoumarins. Treatment with beta-NF did not significantly elevate the rate of metabolism of any of the alkoxyquinolines. DEX treatment produced significant elevations in the rate of metabolism of benzyloxy-, ethoxy-, and butoxy- = pentoxy- = propoxyquinoline, in that order. ISF treatment significantly elevated the rate of metabolism of benzyloxy-, methoxy- and butoxyquinoline, in that order. These results suggest that some of these new fluorescent substrates can be used to characterize induction of rainbow trout hepatic microsomal monooxygenase activity by ISF and DEX, in addition to the commonly used ethoxyphenoxazone and ethoxycoumarin for the characterization of induction by beta-NF or other 3-methylcholanthrene-type P450 inducers. Distinction between ISF-type and beta-NF-type inducers in rainbow trout hepatic microsomes may best be made using 7-methoxycoumarin as a substrate. Distinction between ISF-type and DEX-type inducers and between beta-NF-type and DEX-type inducers may best be made using 7-methoxyphenoxazone as a substrate.(ABSTRACT TRUNCATED AT 400 WORDS)

In vivo effects of the anesthetic, benzocaine, on liver microsomal cytochrome P450 and mixed-function oxidase activities of gilthead seabream (Sparus aurata)

Gilthead seabreams were exposed to benzocaine, 4-aminobenzoic acid ethyl ester, 57 mg/l in sea water for 3 min, daily, for 2 or 3 consecutive days. The fish were killed 20 hr after the last treatment. Benzocaine treatment for 2 or 3 days resulted in 57% and 67% inhibition of liver microsomal aniline 4-hydroxylase and ethylmorphine N-demethylase activities, respectively. The total cytochrome P450 content of fish liver microsomes was unaltered following the 2-day benzocaine treatment. However, additional 3 min benzocaine treatment on day 3 reduced cytochrome P450 level by 50%. Benzocaine produced type II difference spectra with rabbit liver microsomes. Difference spectra of fish liver microsomes elicited by benzocaine were complex. The position of peak and intensity were greatly influenced by the concentration of benzocaine.

Immunological characterization of flavin-containing monooxygenases from the liver of rainbow trout (Oncorhynchus mykiss): sexual- and age-dependent differences and the effect of trimethylamine on enzyme regulation

Polyclonal antibodies raised against flavin-containing monooxygenase (FMO) enzymes purified from pig liver and rabbit lung were used in conjunction with N,N-dimethylaniline (DMA) N-oxidase to better characterize FMO from the liver of rainbow trout (Oncorhynchus mykiss). Two proteins reacted with polyclonal antibodies raised against pig liver FMO (PL-1 and PL-2) and anti-rabbit lung FMO (RL-1 and RL-2). Although there was no difference in DMA N-oxidase observed between sexually mature male and female trout liver microsomes, RL-2 and PL-2 were significantly less than RL-1 and PL-1, respectively, in sexually mature females. FMO activity and protein content increased as fish aged. DMA oxidase and FMO isozymes were unaltered after pretreatment with the endogenous substrate trimethylamine. Since antibodies to the purified mammalian enzymes react with proteins of similar MW in trout, some forms of FMO appear to be structurally conserved through evolution.

Channel catfish liver monooxygenases. Immunological characterization of constitutive cytochromes P450 and the absence of active flavin-containing monooxygenases

Multiple drugs and pesticides are used in the aquaculture of channel catfish in the Southeastern United States. However, little is known regarding the enzymatic metabolism of these chemicals in the fish. Western blots, utilizing polyclonal antibodies raised against five purified rainbow trout liver cytochrome P450 enzymes, revealed at least two protein bands that were approximately 50 kDa (CATL-1) and 53 kDa (CATL-2). Anti-trout LMC3 and LMC4 only hybridized with the 53 kDa protein, whereas anti-trout LMC1, LMC2, and LMC5 recognized both proteins. Cytochrome P450-catalyzed activities (testosterone and progesterone hydroxylases) associated with LMC1 and LMC5 were also found in catfish liver microsomes. These data suggest that at least two constitutive forms of cytochrome P450 are present in the liver of juvenile channel catfish. Western blots utilizing antibodies raised against rabbit-lung flavin-containing monooxygenases (FMO) showed hybridization with two proteins from rainbow trout liver microsomes, but no cross-reaction with microsomes from catfish liver. N,N,-Dimethylaniline N-oxidase and methimazole oxidase were observed in microsomes from trout, but were absent in catfish liver microsomes prepared in three different laboratories. Consequently, FMO do not appear to be present in liver microsomes from channel catfish or they are rapidly degraded during tissue homogenization.

A constitutive form of guinea pig liver cytochrome P450 closely related to phenobarbital inducible P450b(e)

In order to provide evidence that a cytochrome P450 belonging to the IIB subfamily is expressed as a constitutive form in the guinea pig, we tried to purify an isozyme from liver microsomes of untreated guinea pigs by assessing its reactivity with anti-P450b antibody in the present study. One form of cytochrome P450, named P450GP-1, was obtained. The minimum molecular weight of this isozyme was estimated to be 52,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amino terminal sequence up to the 33rd amino acid of P450GP-1 was determined. As expected, comparison of the amino acid sequence with those of cytochrome P450 isozymes from other species reported so far indicated that P450GP-1 was highly homologous to P450s categorized in the IIB subfamily; that is, 67% similarity to rat P450b, 82% to rabbit LM2, 76% to dog PBD-2, 70% to mouse pf 3/46, and 73% to human IIB1. On the other hand, P450GP-1 showed only low similarity, less than 41%, to other cytochrome P450s of the II subfamily and those of the I, III, and IV families. Affinity of P450GP-1 to anti-P450b immunoglobulin G was confirmed to be comparable with that of a principal antigen, P450b. Immunoblot analysis revealed that P450GP-1 in the guinea pig liver microsomes was induced by phenobarbital treatment, but the increase was not as large as in the rat. P450GP-1 efficiently catalyzed benzphetamine N-demethylation, strychnine 2-hydroxylation, and testosterone 16 beta-hydroxylation, all of which are also catalyzed by P450b. Based on these results, it was strongly suggested that the IIB-type of cytochrome P450 in guinea pigs, at least one of them, is a constitutive form which is moderately induced by phenobarbital.

Comparison of rainbow trout and mammalian cytochrome P450 enzymes: evidence for structural similarity between trout P450 LMC5 and human P450IIIA4

Studies were undertaken to determine the immunochemical relationship between constitutive trout cytochrome P450s and mammalian cytochrome P450IIIA enzymes. Polyclonal antibodies (IgG) generated against trout P450 LMC5 reacted strongly with P450IIIA1 in dexamethasone-induced rat liver microsomes and with P450IIIA4 in human liver microsomes in immunoblots. In contrast, rabbit anti-P450 LMC1 IgG did not recognize these proteins in rat and human liver microsomes. Reciprocal immunoblots using anti-rat P450IIIA1 showed that this antibody does not recognize trout P450 LMC1 or LMC5. However, anti-human P450IIIA4 IgG was found to cross react strongly with P450 LMC1 and LMC5. Progesterone 6 beta-hydroxylase activity of trout liver microsomes, a reaction catalyzed by P450 LMC5, was markedly inhibited by anti-P450IIIA4 and by gestodene, a mechanism-based inactivator of P450IIIA4. These results provide evidence for a close structural similarity between trout P450 LMC5 and human P450IIIA4.

Initial purification and characterization of hepatic microsomal cytochrome P-450 from BNF-treated perch (Perca fluviatilis)

1. A procedure was developed for isolating and purifying cytochrome P-450 from hepatic microsomes of BNF-treated perch, using modified versions of the methods of Williams and Buhler (1982. Biochim. biophys. Acta 717, 398-404) and Goksøyr (1985. Biochim. biophys. Acta 850, 409-417). 2. Following chromatography on phenyl-Sepharose CL 4B and DEAE-Sepharose CL-6B, the major peaks, fractions b and c, were resolved into five fractions, possibly representing different isoenzymes, by a FPLC with a strong anion exchange column (Mono Q). 3. These fractions have been characterized on the basis of their spectral, electrophoretic and immunological properties. 4. The purified form of cytochrome P-450 in fraction V from perch liver showed a number of similarities to cytochrome P-450c, the major BNF-inducible cytochrome P-450 in cod liver. 5. Therefore we suggest that this purified form of cytochrome P-450 is a BNF-induced form in perch and that it is closely related to the gene subfamily cytochrome P-450 IA1.

Regiospecificity in the hydroxylation of lauric acid by rainbow trout hepatic cytochrome P450 isozymes

The catalytic activity of two hepatic cytochrome P450 isozymes from untreated rainbow trout towards lauric acid was investigated. In a reconstituted system, cytochrome P450 LMC1 and P450 LMC2 were found to catalyze exclusively the omega- and (omega-1)-hydroxylation of lauric acid, respectively. Microsomal enzyme inhibition studies with polyclonal antibodies raised against the individual P450 isozymes showed that P450 LMC1 and LMC2, respectively, accounted for most if not all the omega- and (omega-1)-lauric acid hydroxylase activity of trout liver microsomes. The polyclonal antibodies were highly specific in that they only inhibited the enzyme activity of the P450 used as the immunogen. These results illustrate that as in mammals, omega- and (omega-1)-hydroxylation of lauric acid by trout liver microsomes can be carried out separately by distinct isozymes of cytochrome P450.

Immunological characterization of constitutive isozymes of cytochrome P-450 from rainbow trout. Evidence for homology with phenobarbital-induced rat P-450s

Immunoglobulin G fractions (IgGs), isolated from rabbits immunized against hepatic cytochrome P-450 isozymes were used to investigate the immunochemical homology among trout P-450s and between trout and rat P-450s. The antigens used for immunization were five constitutive trout P-450s (LMC1 to LMC5), one beta-naphthoflavone (BNF)-inducible trout P-450 (LM4b), and one phenobarbital-induced rat P4500IIB1 (PB-B). In the enzyme-linked immunosorbent assay (ELISA), strong cross-reactivity was observed between anti-LMC2 IgG and P-450 LMC1, and between anti-LMC3 IgG and P-450 LMC4. There was little or no cross-reactivity of anti-LMC5 IgG with other trout P-450s. Trout P-450 LM4b was not recognized by any of the antibodies against constitutive trout P-450s. Antibodies to P-450 LMC1 and P450 LMC2 cross-reacted strongly with rat P450IIB1 and with proteins of PB-induced rat liver microsomes. Rat P450IA1 (BNF-B) did not cross-react with anti-LMC1 or anti-LMC2 IgG. These cross-reactions were essentially confirmed by immunoblot (Western blot) analysis. Western blots of PB-induced rat liver microsomes probed with anti LMC1 revealed two major immunoreactive proteins in the P-450 region, one of which co-migrated with rat P450IIB1. P450IIB1 itself cross-reacted strongly with anti-LMC1 IgG. In control rats, a single protein band cross-reacted poorly with anti-LMC1 IgG. Antibodies to LMC1 and LMC2 did not cross-react with rat P450IA1 in Western blots. The antigenic epitopes in rat P450IIB1 recognized by anti-LMC1 IgG and anti-LMC2 IgG are probably not located at or near the active site of the enzyme since these antibodies did not inhibit benzphetamine N-demethylase activity of P450IIB1 or of PB-induced rat liver microsomes. In general, our results demonstrate: (1) the presence of a significant homology between LMC1 and LMC2, and between constitutive trout P-450 (LMC1) and PB-induced rat P-450 (P450IIB1); and (2) distant homology between constitutive trout P-450s and constitutive rat P-450s or BNF-induced rat P-450s.

Mechanisms of anti-carcinogenesis by indole-3-carbinol. Studies of enzyme induction, electrophile-scavenging, and inhibition of aflatoxin B1 activation

The induction of oxidation and conjugation enzymes, the scavenging of carcinogen electrophiles, and the inhibition of aflatoxin B1 (AFB1) activation were examined as possible mechanisms of anti-carcinogenesis by indole-3-carbinol (I3C). Liver microsomal 7-ethoxycoumarin O-deethylase and 7-ethoxyresorufin O-deethylase activities were not induced significantly in rainbow trout fed diets containing 500-2000 ppm I3C for 8 days compared to trout fed the control diet. Furthermore, no detectable changes in the specific contents of cytochrome P-450 isozymes LM2 and LM4b, as measured by Western-blotting and immunoquantitation, were found in liver microsomes following dietary I3C administration. Dietary I3C had no significant effect on liver microsomal uridine diphosphate-glucuronyl-transferase activity, measured using the substrates 1-naphthol and testosterone, or on cytosolic glutathione S-transferase activity, measured using the substrate styrene oxide. The ability of I3C or its acid reaction products (RXM; generated by the reaction of I3C with HCl) to act as scavengers for the direct alkylating agent AFB1-8,9-Cl2 was examined. Addition of I3C or RXM to in vitro incubations did not inhibit the covalent binding of AFB1-8,9-Cl2 to calf thymus DNA. Kinetic analyses of microsome-mediated binding of AFB1 to DNA in vitro indicated that RXM inhibited the metabolic activation of AFB1. RXM increased the apparent Km for the AFB1-DNA binding reaction without changing the associated Vmax; the apparent Km values at 0, 3.5, 35, and 350 microM RXM were 35, 38, 66, and 86 microM for trout liver microsomes. RXM also inhibited the activation of AFB1 by rat liver microsomes, but I3C was not an effective inhibitor against AFB1-DNA binding mediated by either rat or trout liver microsomes. The results of the present study indicate that inhibition of microsome-activated AFB1 binding to DNA by I3C products may be of significant importance in I3C inhibition of hepatocarcinogenesis in trout and other species. The inhibition of carcinogen activation by I3C is contrasted with the mechanism of anti-carcinogenesis by beta-naphthoflavone, which involves induction of xenobiotic metabolizing enzymes.

Cytochrome P450 forms in fish: catalytic, immunological and sequence similarities

1. Hepatic microsomal enzymes from teleost and elasmobranch fishes catalyse a diversity of monooxygenase reactions, consistent with the presence of multiple, distinct P450 forms. Protein purification and immunological studies have confirmed that multiple microsomal P450s occur in teleosts. 2. A member of the aromatic hydrocarbon-inducible P450 IA family is present in all fish species examined to date. This protein appears to be most closely related to P450 IA1. Certain of the immunological probes for a teleost P450 IA1 (scup P450E) appear to be reagent antibodies, recognizing the homologous protein in members of all vertebrate groups examined. The nature of the epitope recognized by such antibodies is not known. 3. Based on immunological and amino acid sequence comparisons, teleost P450 IA1 appears to be orthologous to both P450 IA1 and P450 IA2 in mammals. Multiple P450 IA genes may appear in teleosts, but divergence on separate lines from that involving mammalian P450 IA2 could include additional, new members (P450 IA3?) of the P450 IA family. 4. There are greater similarities in the N-terminal amino acid sequences of different teleost (scup and trout) P450 IA1 forms, than seen in the N-terminal sequence relationships found in P450 IA1 of mammalian species. Whether this similarity extends to the rest of these teleost proteins is unknown. 5. The induction of P450 IA1 in teleosts involves transcriptional and translational events. However, the temporal patterns involved in induction of mRNA or protein are different from those in mammalian species, indicating additional aspects of the regulation in teleosts. 6. Relationships between other teleost and mammalian P450 forms, or between other P450 forms isolated from different teleosts, remain to be conclusively established. However, certain relationships are suggested, based on catalytic and other comparisons.

Determination of multiple forms of cytochrome P-450 in microsomes from the digestive gland of Cryptochiton stelleri

Polyclonal antibodies raised against purified trout cytochromes P-450 (P-450) LM2 (anti-LM2) and LM4b (anti-LM4b) were used in Western blot analyses with digestive gland microsomes from control and beta-naphthoflavone (BNF)-treated gumboot chitons Cryptochiton stelleri. An increase and decrease in staining intensity subsequent to treatment with anti-LM4b and anti-LM2, respectively, was observed in digestive gland microsomes from BNF-treated chiton. Thus, there appears to be at least two forms of P-450 in microsomes from the digestive gland of Cryptochiton; one of which is induced by BNF and perhaps is involved in benzo(a)pyrene (BP) biotransformation, and another form which is inhibited by BNF.