Further Studies on the Action of Prolactin on Fluid and Ion Absorption by the Rat Jejunum

Abstract

The influence of administration of ovine prolactin in vivo on intestinal fluid and ion transport in vitro was investigated using intact and hypophysectomized male rats. Prolactin administration significantly stimulated fluid, sodium,potassium, calcium, magnesium and chloride transport across everted jejunal sacs. The last two ions were affected less than the others. Hypophysectomy caused a significant decrease in fluid and sodium absorption, but prolactin treatment for 2 days restored normal absorption rates but not uniformly in all sacs. Prolactin action on fluid and sodium absorption showed a dose-dependent tendency, maximal stimulation resulting from administration of 1.0 to 2.0 mg prolactin daily; higher doses failed to elicit significant response. The stimulatory action of prolactin was inhibited by a simultaneous administration of vasopressin which when given alone had no effect on intestinal absorption. In the absence of glucose or in the presence of phlorizin, fluid transport was inhibited, the reduction being more dramatic in the presence of phlorizin. Similarly, either application of ouabain or partial replacement of sodium with isotonic choline chloride reduced fluid transport. Although these in vitro treatments nullified the stimulatory effects of prolactin, only phlorizin and ouabain significantly decreased sodium transport. These results suggest that the effects of prolactin on intestinal transport may be dependent on increased movement of sodium.

Further Evidence of Prolactin Production from Human Decidua and Its Transport across Fetal Membrane

“…Regard ing the physiological meaning of amniotic fluid PRL, there are many reports that are involved in the balance of water and electro lytes [24,25], the maturation of fetal lungs [26] and so on [27][28][29]. The origin, produc tion and secretion mechanism, and roles of amniotic fluid PRL are thus awaiting further investigation.…”

Acute Effect of Prolactin on Bone 45Ca Accumulation in Rats.

“…Chronic administration of PRL has been reported to indirectly enhance the in vitro duodenal [5] and jejunal [6] active calcium absorption by stimulating renal production of 1,25(OH)2D [7]. The possibility of PRL having an acute and direct effect on calcium absorption was first indicated by our earlier observations that a pharmacological dose of 0.02 mg PRL/100 g body weight enhanced calcium absorption as early as 60 min [8,9].…”

Prolactin and Osmoregulation in Vertebrates

“…Intestinal sacs have been used for some time to de monstrate the stimulatory effect of prolactin on Na*, Cl and water absorption [117][118][119][120][121][122]169]. Other experiments de monstrate that prolactin also stimulates intestinal Ca2 transport [53,120] (and bone Ca-'* mobilization [150]); this may be one effect contributing to the hypercalcemic action mentioned above. However, hyperprolactinemia and its al leviation in female humans did not alter the secretion of various calciotropic hormones [161 b].…”