Plasma prolactin and puerperal blood pressure

Prolactin induces regional vasoconstriction through the beta2-adrenergic and nitric oxide mechanisms

Prolactin has been associated with many effects and has been implicated in the pathogenesis of pregnancy-related hypertensive disorders, although little is known about its vascular effects. The present study was designed to determine the primary effect of prolactin on regional vascular beds and the mechanisms involved. In 37 anesthetized pigs, the infusion of 0.17 mug/kg min of prolactin at constant heart rate and arterial pressure decreased coronary, mesenteric, renal, and iliac blood flow. This response was graded in further five pigs by increasing the infused dose of the hormone between 0.017 and 1 mug/kg min. In 22 of the 37 pigs, blockade of cholinergic receptors (five pigs) and of alpha-adrenoceptors (five pigs) did not affect the prolactin-induced vascular response, which was abolished by blockade of beta(2)-adrenoceptors (five pigs) and by blockade of vascular nitric oxide (NO) synthase (seven pigs). In 15 of the 37 pigs the increases in measured blood flows caused by iv infusion of isoproterenol (five pigs) and by intraarterial administration of acetylcholine (five pigs) and of sodium nitroprusside (five pigs) were significantly reduced by infusion of prolactin. Moreover, the treatment of porcine aortic endothelial cells by prolactin caused a reduction of NO production and of the phosphorylation of ERK, Akt, and p38, which was prevented by the concomitant treatment by the beta(2)-adrenergic agonist albuterol. The present study showed that iv infusion of prolactin primarily caused coronary, mesenteric, renal, and iliac vasoconstriction. These effects were brought about by the inhibition of a vasodilatory beta(2)-adrenergic receptor-mediated effect related to the NO intracellular pathway.

A prospective study of circulating prolactin during primigravid pregnancy

A prospective, cross-sectional study of 164 primigravid patients was conducted to determine the role of prolactin in the pathogenesis of pregnancy induced hypertension. Clinically normal patients had peripheral venous blood sampled from the lateral and recumbent positions monthly in the morning during their last two trimesters in labor and six weeks postpartum. One-third of the patients had 24 hour urine collections. Homologous double antibody radioimmunoassays were performed to determine prolactin levels. The data were analyzed according to pregnancy outcome: pregnancy-induced hypertension or normotensive throughout pregnancy. Acute positional change did not influence prolactin level. Prolactin levels were significantly elevated in the hypertensive outcome group only at 37-39 weeks and were not correlated with sodium excretion. We conclude that circulating prolactin does not play a significant role in pathogenesis of pregnancy-induced hypertension, but perhaps the elevated levels may be reflecting pathophysiologic changes.