Stimulation of rat ovarian ornithine decarboxylase in vitro by hCG, amino acids and bovine serum albumin

Abstract

Rat ovarian ornithine decarboxylase activity could be stimulated in vitro by a variety of factors, which apparently have different modes of action. Ovarian cells prepared from pre-pubertal rats by collagenase dispersion exhibited a low but detectable ornithine decarboxylase activity after a 6-h incubation in a defined medium. The enzyme activity as markedly enhanced in vitro by hCG, which also produced increased accumulation of cyclic AMP and stimulated the secretion of progesterone. In addition to the gonadotrophin, ovarian ornithine decarboxylase activity was strikingly stimulated by some non-essential amino acids, and especially by bovine serum albumin. While markedly enhancing ornithine decarboxylase activity, none of the latter additions increased the accumulation of cyclic AMP or enhanced the secretion of progesterone. Bovine serum albumin enhanced powerfully ornithine decarboxylase activity in vitro at very small concentrations (from 0.75 muM). The half-life of the enzyme remained unchanged (26-28 min) upon stimulation indicating that the stimulation mechanism did not involve any stabilization of the enzyme.