In vivo effect of noradrenaline on the cyclic AMP level in rat corpora lutea

Abstract

Under in vitro conditions adrenaline and noradrenaline can stimulate the production of cyclic AMP in rat corpora lutea to a similar extent as a maximal dose of LH. The present study was undertaken to compare the effects of noradrenaline and LH under in vivo conditions. Anaesthetized rats bearing 2 days old corpora lutea were either infused intraarterially with noradrenaline (0.4 microgram/min) or given a single intraarterial injection of 5 micrograms LH. The cAMP levels in whole ovaries had increased already after 30 sec of noradrenaline infusion. These levels remained high for a few minutes and, thereafter the effect decreased with time. No effect was seen after 20 min of infusion. Infusion of noradrenaline for 20 min increased cAMP in corpora lutea, but not in non-luteal tissue. LH was effective both in luteal and non-luteal tissue. The results show that noradrenaline in vivo can increase the cAMP content only in corpus luteum and within a rather short time period (5 min). This effect is different from that seen with LH which, instead, acts on both corpus luteum and stromal tissue.