REGULATION OF BOVINE AND OVINE LYMPHOCYTE-PROLIFERATION BY PROGESTERONE - MODULATION BY STEROID-RECEPTOR ANTAGONISTS AND PHYSIOLOGICAL STATUS

Lectin-stimulated sheep and cow lymphocytes were used to test whether inhibitors of classical steroid receptors block suppressive effects of progesterone and whether effects of progesterone vary with physiologi cal status. Neither RU 38486 nor RU 43044 blocked the inhibitory effec ts of progesterone on lymphocyte proliferation. Rather, these antagoni sts were themselves inhibitory. Effects of progesterone and antagonist s were additive: the percentage inhibition caused by progesterone was similar whether antagonists were present or not. The degree of lymphoc yte proliferation and the inhibitory effects of progesterone were of t he same magnitude for pregnant/lactating cows, pregnant/non-lactating cows, postpartum/lactating cows and cyclic/non-lactating cows. In conc lusion, progesterone does not appear to inhibit lymphocyte proliferati on through actions that involve classical steroid receptors. There was no evidence that lymphocyte proliferation in the cow is suppressed du ring pregnancy or that the inhibitory effects of progesterone increase during pregnancy.