INHIBITION OF P-NITROPHENOL GLUCURONIDATION BY CALCIUM MOBILIZING HORMONES

1. Vasopressin and phenylephrine markedly inhibited the glucuronidatio n of p-nitrophenol in isolated murine hepatocytes. 2. After longer pre incubation of hepatocytes in the presence of vasopressin or phenylephr ine the rate of conjugation began to return to the control values indi cating the reversibility of the inhibition caused by these agents. 3. The inhibitory effect of both agents was dependent on the Ca2+ filled state of the intracellular stores. 4. The inhibition caused by the alp ha 1 receptor agonist phenylephrine was receptor mediated because it c ould be prevented by the addition of alpha 1 antagonist prazosin. 5. T he data support the theory that the maintenance of the intralumenal Ca 2+ concentration is necessary for the optimal activity of p-nitropheno l UDP-glucuronosyl-transferase.