Biomedical subjects

Yasuo Ohno

Publications and source records attributed to Yasuo Ohno.

58 records · Page 4Linked to original sources

PubMed2002

CYP3A4 gene polymorphisms influence testosterone 6beta-hydroxylation.

Three non-synonymous single nucleotide polymorphisms (SNPs) in the CYP3A4 gene were found in 34 cell lines derived from Japanese individuals. These three SNPs (T185S, L293P, and T363M)(1) have been previously reported, but little is known about the effect that these polymorphisms, especially T185S, have on catalytic activity. We measured testosterone hydroxylation in wild-type CYP3A4 and these three variants using a mammalian expression system. Testosterone 6beta-, 2beta-, and 15beta-hydroxylations by the variant CYP3A4 forms T363M (<40%) and T185S (<60%) were reduced as compared with the wild-type in transient expression assays. L293P was similar to the wild-type in testosterone 6beta- and 2beta-hydroxylase activities. Western blot analysis confirmed lower amounts of CYP3A4 protein in the T363M and T185S variants than in the wild-type. Interestingly, Northern blot analysis showed no significant difference among mRNA levels between the wild-type and variants. These results suggest that the T363M and T185S substitutions in CYP3A4 affect either protein expression or stability. These established cell lines provided useful CYP3A4 SNP information in the Japanese.

Journal Article↗

PubMed2002

Effects of serum albumin and liver cytosol on CYP2C9- and CYP3A4-mediated drug metabolism.

To investigate whether the free-drug theory is accurate in that only unbound drug is available for drug metabolism or enzyme inhibition. The effect of addition of rat liver cytosol to an in vitro system using human liver microsomes was examined by measuring the catalytic activities of CYP2C9 (tolbutamide and diclofenac) and CYP3A4 (terfenadine). And, the results were compared with those obtained when human serum albumin (HSA) was added to microsomes as far as unbound drug concentrations were concerned. After addition of rat liver cytosol, the unbound Km value (Km,u) for terfenadine metabolism by CYP3A4, and the unbound Ki value of miconazole (Ki,u) for CYP2C9 were smaller than for the controls. Addition of HSA resulted in smaller Km,u values for diclofenac and terfenadine metabolism by CYP2C9 and CYP3A4, respectively, and the Ki,u value for ketoconazole inhibition of CYP3A4 was also reduced. These results suggest protein-facilitated effects on drug metabolism and enzyme inhibition for both CYP2C9 and CYP3A4. However, no protein-facilitated drug metabolism was observed for tolbutamide in the presence of HSA or cytosol, or for diclofenac in the presence of cytosol. Protein-facilitated enzyme inhibition did not occur with miconazole in the presence of HSA or with ketoconazole in the presence of rat liver cytosol. Protein-facilitated metabolism and enzyme inhibition were observed for CYP2C9 and CYP3A4 in five cases but there was no obvious pattern of enzyme, substrate, or binding protein specificity. Further investigations are necessary to clarify the relevance of these results to in vivo observations.

Journal Article↗

PubMedDate not supplied

Preparation of complement fragments C3b and C3a from purified rat complement component C3 by activated cobra venom factor.

INTRODUCTION: Complement component C3 (C3) can be a target of pharmacological or toxicological agents. In the analysis of this, it is important to examine the involvement of fragments C3b and C3a since C3 function normally requires cleavage into these fragments. The present study describes a simple and efficient method for the preparation of rat complement C3b and C3a by using purified C3 and cobra venom factor (CVF) as a cleaving enzyme. METHODS: CVF was purified from lyophilized cobra venom (Naja naja kausia) by two-step chromatography and was activated by incubation with human factors B and D. C3 was cleaved by incubation with activated CVF (CVF,Bb), and C3b and C3a were isolated by anion- and cation-exchange chromatography, respectively. RESULTS: About 200 microg of CVF was purified from 100 mg of cobra venom. All the CVF was activated by incubation with factors B and D. The C3b and C3a obtained were pure as analyzed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, and no digestive by-products such as C3f were found. DISCUSSION: The advantage of the present method is that it is possible to prepare relatively large amounts of C3b by simple procedures without digestive by-products. C3a can be prepared from the flow through fraction of the C3b purification. C3b and C3a prepared by the present method would be useful for pharmacological or toxicological experiments involving receptor binding since their binding sites remain intact.

Animals↗

PubMedDate not supplied

Comparison of motor reactivity of the colonic muscularis mucosae isolated from human, guinea pig and rat in vitro.

We have compared the reactivity to spasmogens of longitudinal muscularis mucosae isolated from the human, guinea pig and rat colon in vitro. The muscularis mucosae isolated from the human distal colon responded with a sustained contractions to carbachol (10 nM-30 microM), in a concentration-dependent manner, and the maximum contraction was comparable to that with high potassium concentration (100 mM). Among several spasmogens, neurokinin A was the most potent with the following order of potency: carbachol, prostaglandin F2alpha and acetylcholine. Histamine, 5-hydroxytryptamine and bradykinin did not produce a recognizable contraction of this tissue. The muscularis mucosae isolated from the guinea pig distal colon demonstrated a concentration-dependent contraction in response to neurokinin A, carbachol, histamine and acetylcholine, but not to prostaglandin F2alpha or 5-hydroxytryptamine, and the maximum contraction was obtained with histamine. The muscularis mucosae from the rat distal colon was very sensitive to neurokinin A and bradykinin, less to carbachol and acetylcholine, and not at all sensitive to histamine, 5-hydroxytryptamine and prostaglandin F2alpha. It is concluded that the colonic muscularis mucosae respond to pharmacological agents in a species-different manner.

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