Effect of elevated prolactin levels on the synthesis and release of catecholamines from the adrenal medulla in female rats

Abstract

Recent evidence suggests that increased plasma prolactin (PRL) levels could be modifying the synthesis and release of catecholamines (CA) from the adrenal medulla. In order to study this possibility, female rats bearing an anterior pituitary gland, from a litter-mate donor, under the right kidney capsule since day 30 of life and their sham-operated controls were sacrificed by decapitation 45 days after the transplant operation. Plasma PRL and CA levels and CA content in the adrenal medulla were analyzed. A significant increase in plasma PRL levels was shown in grafted (22 +/- 2 micrograms/l) when compared to control rats (6 +/- 0.3 micrograms/l), together with a significant increase in plasma norepinephrine (NE) (4.2 +/- 1.1 micrograms/l vs. 1.7 +/- 0.7 micrograms/l) and epinephrine (E) (2.9 +/- 0.6 micrograms/l vs. 1.6 +/- 0.2 micrograms/l). Similar plasma dopamine (DA) levels were found in both groups (0.6 +/- 0.2 micrograms/l vs. 0.8 +/- 0.3 micrograms/l). An increase in adrenal DA content (29.1 +/- 6.8 ng/mg protein), together with a decrease in NE (33.3 +/- 6.8 ng/mg protein) and E content (65.9 +/- 11.8 ng/mg protein) was detected in grafted as compared to control rats (DA: 12.0 +/- 3.6 ng/mg protein; NE: 79.3 +/- 22.1 ng/mg protein; E: 184.2 +/- 39.2 ng/mg protein). We can conclude from these data that the elevation of circulating PRL levels induced by a pituitary graft is able to increase the synthesis and release of CA from the adrenal medulla in female rats.