Hepatic UDP-glucuronyltransferase in Wistar and Gunn rats - in vitro activation by diethylnitrosamine

Stevenson, I. H.; Greenwood, D. T.; McEwen, John

doi:10.1016/0006-291x(68)90321-5

Cited by 49 publications

(18 citation statements)

References 7 publications

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“…However, it seems possible that many data on UDP glucuronyltransferase must be greatly modified by the use of detergents in the measurement of the enzyme activity, as exemplified by the effect of Triton X-100 and the effect of the carcinogen diethylnitrosamine on UDP glucuronyltransferase activity from the liver of Gunn rats towards o-aminophenol. Whereas enzyme preparations from the livers of these rats have a very low o-aminophenol-glucuronidating activity, this can be increased by diethylnitrosamine in vitro to the same value as that in the diethylnitrosamine-activated enzyme from normal rat liver (Stevenson, Greenwood & McEwen, 1968). Moreover, Halac & Sicignano (1969) who activated their enzyme preparations by dialysis against EDTA-mercaptoethanol, could not find the previously described (Inscoe & Axelrod, 1960) sex difference in the glucuronidation of p-nitrophenol and bilirubin in homogenates from male and female rat livers.…”

Section: Discussionmentioning

confidence: 95%

The effect of phenobarbital on the submicrosomal distribution of uridine diphosphate glucuronyltransferase from rat liver

Mulder

1970

Biochemical Journal

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1. The detergent Triton X-100 activates UDP glucuronyltransferase from rat liver in vitro six- to seven-fold with p-nitrophenol as substrate. The enzyme activity when measured in the presence of Triton X-100 is increased significantly by pretreatment of male rats with phenobarbital for 4 days (90mg/kg each day intraperitoneally). If no Triton X-100 is applied in vitro such an increase could not be shown. In all further experiments the enzyme activity was measured after activation by Triton X-100. 2. The K(m) of the enzyme for the substrate p-nitrophenol does not change on phenobarbital pretreatment. 3. When the microsomal fraction from the liver of untreated rats is subfractionated on a sucrose density gradient, 47% of the enzyme activity is recovered in the rough-surfaced microsomal fraction, which also has a higher specific activity than the smooth-surfaced fraction. 4. Of the increase in activity after the phenobarbital pretreatment 50% occurs in the smooth-surfaced fraction, 19% in the rough-surfaced fraction and 31% in the fraction located between the smooth- and rough-surfaced microsomal fractions on the sucrose density gradient. 5. The latency of the enzyme in vitro, as shown by the effect of the detergent Triton X-100, is discussed in relation to the proposed heterogeneity of UDP glucuronyltransferase.

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Section: Discussionmentioning

confidence: 95%

The effect of phenobarbital on the submicrosomal distribution of uridine diphosphate glucuronyltransferase from rat liver

Mulder

1970

Biochemical Journal

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“…Another possible explanation for the different degrees of latency is the existence of different conformational forms of the enzyme protein itself. Diethylnitrosamine probably exerts its primary effect on the enzyme and not the microsomal membrane because 1) the effect is confined to one species (rat) and two substratss (u-aminophend and paracetamol) and 2) it activates the enzyme "solubilized" by digitonin (STEVENSON et al 1968). Since there is no activating effect of diethylnitrosamine on the hepatoma cell enzyme, this might therefore indicate that a different enzyme form is present in these cells.…”

Section: Discussionmentioning

confidence: 99%

“…The activity in vitro 04 this enzyme is increased several-fold by many compounds. Thus detergents (LUEDERS & KUFF 1967;WINSNES 1969), UDP-Nacetylglucmamine (POGELL & LELOIR 1961;WINSNES 1969) and diethylnitrosamine (STEVENSON et al 1968;WINSNES 1969) when added to liver homogenates may enhance glucuronyltransferase activity up to 20-fold. The available evidence suggests that this is an activation at V,,, (VESSEY & ZAKIM 1971;WINSNES 1972) indicating that more active sites are made accessible for the substrate(s).…”

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confidence: 99%

Different Properties of Microsomal UDP‐Glucuronyltransferase in Buffalo Rat Liver and a Clonal Strain of Rat Hepatoma Cells Derived from the Same Rat Strain

Winsnes

Rugstad

1973

Acta Pharmacologica et Toxicologica

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Abstruct:Optimal conditions for the synthesis of o-aminophenol and p-nitrophenol glucuronides by a clonal strain of rat hepatoma cells (MHIC1) in culture were established. Properties of glucuronyltransferase (UDP-glucuronate glucuronyltransferase (acceptor unspecific), E. C. 2.4.1.17) in homogenates of cultured hepatoma cells, subcutaneous tumours derived from these cells in rats, as well as livers of Buffalo rats were studied. In rat liver 83-90 % and 92-95 % of the glucuronyltransferase activity in homogenates to p-nitrophenol and o-aminophenol respectively were latent, the latency being most pronounced in male animals. With homogenates of cultured hepatoma cells, on the other hand, digitonin activated 1.3 and 1.8-fold only with p-nitrophenol and o-aminophenol as acceptors; other potential activators (Triton X-l 00, UDP-N-acetylglucosamine and diethylnitrosamine) were either without effect or inhibited the enzyme. A I .5-2-fold higher degree of activation of glucuronyltransferase was found in homogenates of hepatoma tumours derived from the same cells injected subcutaneously into Buffalo rats. The specific activity of fully activated glucuronyltransferase in homogenates of cultured hepatoma cells was, however, 2-6.5-fold higher than that of the fully activated rat liver enzyme. The rate of p-nitrophenol glucuronide synthesis by cultures of hepatoma cells increased up to a concentration of 0.10 mM of the aglycone in the growth medium. At concentrations of 0.3 mM and higher, a peculiar lag period was seen before any glucui-onide appeared in the medium. This phenomenon was not seen with o-aminophenol as acceptor and not in broken cell preparations with either substrate. The maximal rate of o-aminophenol glucuronidation in cultures of the hepatoma cells corresponded to that found for homogenates with 0.254.50 mM UDPglucuronate added to the incubation mixture. This value is in good agreement with the presumed intracellular levels of UDP-glucuronate in the liver cell in vivo.

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“…Homozygous Gunn rats exhibit practically no capacity for bilirubin glucuronidation (Carbone and Grodsky, 1957;Schmid et al, 1958;Arias et al, 1963), whereas for some exogenous compounds like p-nitrophenol (Van Leusden et al, 1962;Temple et al, 1968;Jansen and Henderson, 1972;Zakim et al, 1973) almost normal activities have been re ported. However, in some cases UDP-glucuronosyl transferase activity for p-nitrophenol is lower in Gunn than in normal Wistar rats (Drucker, 1968;Stevenson et al. 1968;Yeary and Fleming, 1971;Puukka et al, 1973;Vainio and Hietanen, 1974a, b).…”

mentioning

confidence: 99%

“…1968;Yeary and Fleming, 1971;Puukka et al, 1973;Vainio and Hietanen, 1974a, b). The basic defect in the Gunn rat has been suggested to involve either enzyme-lipid interaction in the microsomal membrane (Stevenson et al, 1968;Zakim et al, 1973) or synthesis of UDP-glucuronosyl transferase ( Vainio and Hietanen, 1974a, b).…”

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confidence: 99%

Drug Conjugation in Gunn Rats: Reduced UDP-Glucuronosyl Transferase and UDP-Glucosyl Transferase Activities with Increased Glycine-N-Acyltransferase Activity

Marniemi¹,

Vainio²,

Parkki³

1975

Pharmacology

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Glucuronyl, glucosyl, glutathione, glycine conjugations and epoxide hydration were studied in livers of Wistar and Gunn rats. The activities of bilirubin UDP-glucuronosyl transferase and UDP-glucosyl transferase were reduced in microsomes of homozygous and heterozygous Gunn rats compared to Wistar rats (over 90 and 55–65 %, respectively). Conjugation of 4-methylumbelliferone by UDP-glucuronosyl transferase was also reduced (30–35 %) in Gunn rats. Treatment of microsomes in vitro with membrane perturbating agents increased the measurable activities but did not change the activity relationships between Wistar and Gunn rats. Microsomal epoxide hydrase and soluble glutathione-S-epoxide transferase activities occurred in Gunn rats at the Wistar level, but mitochondrial glycine-N-acyltransferase activity was elevated in homozygous and heterozygous Gunn rats (66 and 47 %, respectively). The reciprocal velocity plots of UDP-glucuronosyl transferase activity were similarly concave in Gunn and Wistar rats.

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Hepatic UDP-glucuronyltransferase in Wistar and Gunn rats - in vitro activation by diethylnitrosamine

Cited by 49 publications

References 7 publications

The effect of phenobarbital on the submicrosomal distribution of uridine diphosphate glucuronyltransferase from rat liver

The effect of phenobarbital on the submicrosomal distribution of uridine diphosphate glucuronyltransferase from rat liver

Different Properties of Microsomal UDP‐Glucuronyltransferase in Buffalo Rat Liver and a Clonal Strain of Rat Hepatoma Cells Derived from the Same Rat Strain

Drug Conjugation in Gunn Rats: Reduced UDP-Glucuronosyl Transferase and UDP-Glucosyl Transferase Activities with Increased Glycine-N-Acyltransferase Activity

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