Prolactin Receptors in the Rat Kidney

Abstract

Specific binding of 125I-labelled ovine prolactin iodinated by a lactoperoxidase method was demonstrated in crude membrane preparations of kidneys and adrenals of male Sprague-Dawley rats and livers from female rats. Membrane preparations derived from the 100,000 g fractions of tissue homogenates contained most of the specific prolactin binding. Kinetic and affinity characteristics of prolactin binding to kidney membranes were examined in detail. Maximal specific binding occurred after incubation for 30 h at room temperature. Scatchard analysis indicated that prolactin binding to kidney membranes was of high affinity (dissociation constant = 1.4 x 10(-10) mol/l) and similar to that for liver membranes, although kidney membranes from male rats bound approximately sixfold less prolactin/mg membrane protein than did liver membranes from female rats. Specific prolactin binding was demonstrated in both renal medulla and cortex. Autoradiography showed maximal prolactin binding activity in the epithelial cells of the proximal tubule and faint activity in the tubular cells throughout the nephron. Specificity of uptake by proximal tubular cells was indicated by the gross reduction in prolactin activity when excess ovine prolactin was administered simultaneously. The demonstration of specific binding sites for prolactin localized primarily in the proximal tubules was consistent with renal action of prolactin, predominantly on sodium metabolism.

Detection of In Situ Localization of Long Form Prolactin Receptor Messenger RNA in Lactating Rats by Biotin-Labeled Riboprobe.

“…PRL contributes to the control of salt and water metabolism in mammals [1], and specific uptake of 1251-labeled ovine PRL was seen in proximal tubular cells in rats [40]. In situ hybridization with oligonucleotide probes complementary to PRLRs and PRLRL indicated the localization of both receptor mRNAs in the kidney [13,141, although there was a large discrepancy in the distribution of signals.…”

Endocrine Control of Renal Handling of Solutes and Water in Vertebrates

“…which may be ascribed to (1) a direct antidiuretic action of prolactin, and (2) po tentiation of vasopressin and aldosterone action. However, prolactin preparations of various species are contaminated considera bly by neurohypophysial hormones, and this appears to be responsible for the renal action of prolactin [120], Nonetheless, spe cific prolactin receptors have been demon strated in the proximal tubules of mamma lian kidneys by both radioligand binding and autoradiographic techniques [84], High con centrations of prolactin also have been found in the epithelial cells of the proximal tubules, presumably as the result of trans port across the luminal membrane [34],…”

Altered renal function in chronically hyperprolactinaemic rats.

“…A consequent increase in tubular reabsorptive area would contribute to the enhanced reabsorption observed here. Also of relevance may be the finding that prolactin can bind to tubular cells (Mountjoy, Cowden, Dobbie & Ratcliffe, 1980). Moreover Pippard & Baylis (1986) have shown that the hormone will stimulate Na'-K+-ATPase activity in the outer medulla of the rat kidney.…”