Influence of noradrenaline on progesterone synthesis and posttranslationalprocessing of oxytocin synthesis in the bovine corpus luteum

Noradrenaline (NA) influences secretory function of the bovine corpus luteu m (CL), stimulating secretion of progesterone and ovarian oxytocin (OT). To study whether NA is able to stimulate progesterone synthesis and to affect post-translational OT processing, different doses of NA alone or in combin ation with different doses of OT were added to bovine CL slices from 8 to 1 3 d of the estrous cycle. To determine which receptors NA affects, and if d opamine (DA) also affects CL function, we used NA or DA combined with a bet a-antagonist (propranolol). The results indicated that NA stimulates both l uteal progesterone and OT content, furthermore, it increased the activity o f 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and peptidyl glycine-alp ha-amidating mono-oxygenase (PGA), terminal enzymes in synthesis of these 2 hormones. The stimulating effect of NA was inhibited by propranolol and by pre-treatment of CL slices with high OT doses. Post-translational processi ng of OT synthesis by PGA activation was also stimulated by Dq but this eff ect was inhibited by beta-receptor blocker. Thus DA acts in CL: as a NA pre cursor. In conclusion, it can be assumed that the noradrenergic system affe cts CL secretory function on different levels of regulation. Furthermore, a high concentration of OT in CL prevents NA from activating PGA and thus de creases post-translational OT synthesis. (C) 1999 by Elsevier Science Inc.