Effects of histamine and its blocker on thyrotropin releasing hormone release from rat adrenal gland in vitro

Abstract

The effects of histamine and its blocker on the release of thyrotropin releasing hormone (TRH) from the rat adrenal gland were studied in vitro. Rat adrenals were incubated in medium 199 with 1.0 mg ml-1 of bacitracin and 100 micrograms ml-1 of ascorbic acid (pH 7.4) for 20 min and TRH released into the medium was measured by radio-immunoassay. The immunoreactive TRH (ir-TRH) release from the rat adrenal gland was inhibited significantly in a dose-related manner by the addition of histamine and enhanced by the addition of famotidine. The effect of histamine on ir-TRH release from the rat adrenal gland was blocked by the addition of famotidine to the medium, but not by that of mepyramine. The elution profile of methanol extracted adrenal gland on Sephadex G-10 was identical to that of synthetic TRH. The findings suggest that histamine inhibits TRH release from the rat adrenal gland and that its effects may be mediated via H2-receptor.