Abstract
Extract: The relative participation of bilirubin conjugating systems other than uridine diphosphate glucuronic acid-dependent bilirubin glucuronyl transferase in 21-day pregnant (P) and nonpregmant (NP) rats with and without prior phenobarbital (PB) administration was studied. Relative enzyme activities of 74.5%, 17.6%, and 7.9% were observed for glucuronic acid, xylose, and glucose conjugates, respectively, in untreated NP rats. Pregnancy itself did not alter the relative activities. In response to PB administration, P rats increased activity less than NP animals for all three enzymes. The ratios of the three conjugates remained unchanged in both P and NP groups after PB stimulation.
Speculation: The mechanisms by which pregnancy reduces the stimulatory effect of phenobarbital on bilirubin glucuronyl transferase in the rat while not altering unstimulated enzyme activity remain unexplained.
The induced enzyme may be different from the noninduced enzyme and may, therefore, be susceptible to inhibitors present in increasing concentrations during pregnancy, inhibitors to which the noninduced enzyme is not susceptible. Alternatively, the induced enzyme may be the same as the noninduced enzyme but the reduced stimulation observed may result from either changes in phenobarbital metabolism during pregnancy or a reduced capacity to synthesize enzyme protein during pregnancy.
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Vaisman, S., Lee, K. & Gartner, L. Various Bilirubin Conjugates in Pregnant and Nonpregnant Rats with and without Phenobarbital Treatment. Pediatr Res 10, 111–113 (1976). https://doi.org/10.1203/00006450-197602000-00008
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DOI: https://doi.org/10.1203/00006450-197602000-00008
