Inhibition of p-nitrophenol glucuronidation by calcium mobilizing hormones

Abstract

1. Vasopressin and phenylephrine markedly inhibited the glucuronidation of p-nitro-phenol in isolated murine hepatocytes.

2. After longer preincubation of hepatocytes in the presence of vasopressin or phenylephrine the rate of conjugation began to return to the control values indicating 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 α1 receptor agonist phenylephrine was receptor mediated because it could be prevented by the addition of α1 antagonist prazosin.

5. The data support the theory that the maintenance of the intralumenal Ca²⁺ concentration is necessary for the optimal activity of p-nitrophenol UDP-glucuronosyl-transferase.