H. G. Wells &amp; Rebecca West

Rao, K. Bhaskara; Ray, Gordon N.

doi:10.2307/40129645

Cited by 2 publications

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“…The specific activity of the enzyme of liver microsomal preparations from normal male rats was 8.65+ 0.65(13). This activity is slightly higher than that of liver microsomal fractions from normal female rats [6.13±0.24(10); Rao et al, 1976]. The animals were castrated and enzyme activity was measured 19 days after operation; the value was 8.6±1.7(3).…”

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confidence: 89%

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Steroid glucuronyltransferases of rat liver. Properties of oestrone and testosterone glucuronyltransferases and the effect of ovariectomy, castration and administration of steroids on the enzymes

Rao¹,

Haueter²,

Rao³

et al. 1977

Biochemical Journal

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1. Microsomal preparations from rat liver, kidney and intestine were tested for UDPglucuronyltransferase activity by using oestrone, oestradiol-17f8, oestriol, testosterone, cortisol, cortisone, corticosterone, aldosterone, tetrahydrocortisol and tetrahydrocortisone as substrates. The microsomal preparation from the liver glucuronidated oestrone, oestradiol-17fl and testosterone. 2. The specific activity of the enzyme was significantly higher in livers from female rats than in those from male rats. 3. Testosterone was actively glucuronidated by both sexes. Cortisol, cortisone, corticosterone, aldosterone, tetrahydrocortisol and tetrahydrocortisone were not glucuronidated by any of the three tissues. 4. The non-ionic detergent Lubrol WX activates liver microsomal UDP-glucuronyltransferase 2-3-fold with oestrone and testosterone as substrates. 5. Oestrone glucuronyltransferase was inhibited by oestradiol-17f, predominantly competitively and by testosterone non-competitively. Bilirubin was a non-competitive inhibitor of oestrone glucuronidation. p-Nitrophenol had no effect. 6. Oestrone glucuronyltransferase could not be stimulated by either acute or prolonged treatment of animals with phenobarbital, whereas a single dose of 3-methylcholanthrene led to a moderate stimulation. 7. Ovariectomy leads to a 56% decrease in oestrone glucuronyltransferase activity; administration of oestradiol-17f, induces the enzyme to normal activity after 12 days, and after 15 days the activity is twice the control value.Actinomycin D and cycloheximide block the oestradiol-17fi-induced increase in enzyme activity. 8. Castration has no effect on the activity of testosterone glucuronyltransferase, nor does administration of testosterone influence enzyme activity. The results provide strong evidence for the existence of multiple steroid glucuronyltransferases in the liver of the rat.Oestrogen glucuronyltransferase (UDP-glucuronate-17f,-oestradiol 3-glucuronyltransferase, EC 2.4.1.59) catalyses the transfer of glucuronic acid from UDP-glucuronate to oestrone. In studies in vitro, foreign compounds such as p-nitrophenol, o-aminophenol and phenolphthalein have often been used as substrates for glucuronyltransferases to measure enzyme activity (Dutton, 1971;Winsnes, 1973). Endogenous substrates include bilirubin (Mulder, 1972) and steroid hormones such as oestrone, oestradiol-17.8, oestriol, testosterone (Rao & Breuer, 1969;Rao et al., 1970a Rao et al., ,b, 1972Rao et al., , 1974Gotze et al., 1971) and tetrahydrocorticosterone (Miller et al., 1973). With so many different acceptors, it may be asked what degree of specificity UDPglucuronyltransferase possesses. Our own previous work with steroid substrates, and other evidence Vol. 162 (see Dutton, 1971;Jacobson et al., 1975), suggests multiplicity of the enzyme.As UDP-glucuronyltransferases are inducible (see Conney, 1967), the effects of administration of phenobarbital and 3-methylcholanthrene, two commonly used enzyme-inducing agents, on steroid glucuronyltransferases were investigated. More...

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confidence: 89%

“…A rapid and economic assay to measure oestrone and testosterone glucuronyltransferase activities of microsomal preparations of the liver has been reported (Rao et al, 1976). Briefly, the method consists ofincubation ofthe microsomal fraction with the radioactive steroid (100000c.p.m.…”

Section: Assay Of Udp-glucuronyltransferase Activitiesmentioning

confidence: 99%

Steroid glucuronyltransferases of rat liver. Properties of oestrone and testosterone glucuronyltransferases and the effect of ovariectomy, castration and administration of steroids on the enzymes

Rao¹,

Haueter²,

Rao³

et al. 1977

Biochemical Journal

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“…1 -Naphthol: UDPGT activity was evaluated by the method of Otani et al [24] with a substrate range of 0.05 -0.75 mM. Testosterone: UDPGT and androsterone :UDPGT activities were measured as described by Rao et al [25], over the substrate concentration ranges 0.06 -0.6 mM and 0.025 -0.5 mM, respectively. The assays were performed at optimal concentrations of Lubrol.…”

Section: Enzymatic Assaysmentioning

confidence: 99%

Novel inhibitors and substrates of bilirubin: UDP‐glucuronosyltransferase Arylalkylcarboxylic acids

Fournel‐Gigleux

Shepherd

Carré

et al. 1989

European Journal of Biochemistry

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The in vitro inhibitory potency of 20 structurally related alkanoic and arylalkanoic acids has been investigated on rat liver UDP-glucuronosyltransferase. These compounds were tested on the microsomal and purified enzyme, and a cloned cDNA expressed in COS 7 cell cultures. Among all the acids tested, 7,7,7-triphenylheptanoic acid was the most powerful inhibitor of bilirubin:UDP-glucuronosyltransferase with a lower effect on 1-naphtol, androsterone and testosterone glucuronidation. The inhibition was competitive towards the microsomal and purified bilirubin:UDP-glucuronosyltransferases with Kiapp values of 12.0 microM and 1.6 microM, respectively. Twenty analogues were examined, and the results showed that their inhibitory potency on bilirubin:UDP-glucuronosyltransferase activity was a function of at least three structural features (a) the presence of a hydrophobic triphenyl moiety; (b) the length of the aliphatic chain and (c) the presence of a carboxylic group. These inhibitors were also tested as possible substrates of UDP-glucuronosyltransferases. The strongest inhibitors were poor substrates of rat liver microsomal UDP-glucuronosyltransferases. However, 7,7,7-triphenylheptanoic acid was actively glucuronidated by purified bilirubin:UDP-glucuronosyltransferase, in contrast to its analogues with decreasing alkyl chain length. In addition, glucuronidation of this molecule was enhanced by clofibrate treatment but could not be detected in Gunn rats, which are deficient in bilirubin:UDP-glucuronosyltransferase, further indicating that the glucuronidation of this compound was catalysed by bilirubin:UDP-glucuronosyltransferase. The results suggest that 7,7,7-triphenylheptanoic acid may be a useful structural probe to investigate the molecular basis of glucuronidation of bilirubin and carboxylic acids.

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H. G. Wells & Rebecca West

Cited by 2 publications

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Steroid glucuronyltransferases of rat liver. Properties of oestrone and testosterone glucuronyltransferases and the effect of ovariectomy, castration and administration of steroids on the enzymes

Steroid glucuronyltransferases of rat liver. Properties of oestrone and testosterone glucuronyltransferases and the effect of ovariectomy, castration and administration of steroids on the enzymes

Novel inhibitors and substrates of bilirubin: UDP‐glucuronosyltransferase Arylalkylcarboxylic acids

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