DEFINITION OF PERIOD OF INDUCTION OF DECIDUOMA IN RAT USING ORNITHINE DECARBOXYLASE AS A MARKER OF GROWTH ONSET

Abstract

The activity of uterine ornithine decarboxylase (ODC) [EC 4.1.1.17] was measured during the 24 h after systemic induction of decidualization. Following a latent period of 2.5 h, activity rose and reached a peak of 5.6 .+-. 1.1-fold at 5 h after induction. The activity then declined and a second, lower peak was seen at 21 h. The increase in ODC activity was suppressed by treatment with cycloheximide (50 mg/kg) and dactinomycin, 500 .mu.g/rat, confirming that the enzyme response reflects protein synthesis. The increase and base-line level of ODC activity were suppressed by ergocornine pretreatment (1 mg/rat) which disturbs the endocrine balance of pseudopregnancy. The growth and differentiation of decidual tissue apparently began 2.5 h after application of the induction stimulus.