Interaction of prolactin with adrenal hormones in blood pressure regulation in rats.

This study examined the role of the adrenals in the systolic blood pressure (BP) response to ovine prolactin (oPRL) administration as well as the interaction of oPRL with epinephrine (EPI), norepinephrine (NOR), and corticosterone (CORT) on BP in the rat. After intraperitoneal implantation of 7-day osmotic minipumps releasing 0.6 micrograms oPRL/h in 0.9% NaCl on day 1, BP was measured via tail cuff on days 1, 4, and 7 in adrenalectomized (ADX) and sham-ADX male rats (n = 8/group). BP was also measured in ADX rats receiving CORT (27.0 micrograms/h), EPI (1.7 micrograms/h), NOR (5.0 micrograms/h), CORT + oPRL, EPI + oPRL, and NOR + oPRL by osmotic pump (n = 8/group). All ADX rats not receiving CORT were given 1.0% NaCl replacement for drinking water. oPRL increased BP over 17 days in sham-ADX rats (P less than 0.01) but had no effect in ADX rats. BP also increased over 7 days in ADX animals receiving CORT, EPI (P less than 0.01), and NOR (P less than 0.01). BP responses to CORT + oPRL and EPI + oPRL were similar to those of CORT and EPI alone, respectively. However, the BP response to NOR + oPRL on day 4 was 250% (P less than 0.01) that to NOR alone and similar to NOR alone on day 7. Replacement of CORT + NOR + oPRL did not prolong the oPRL-induced sensitization to NOR. In no instance did oPRL, by itself, alter heart rate. These data suggest that the pressor response to oPRL requires the presence of the adrenal glands and that oPRL transiently potentiates the pressor response to NOR in vivo.