Effects of chronic prolactin administration on renal hemodynamics in the rat

Experiments were performed to measure the systemic and renal hemodynamic effects of chronic PRL administration to female rats (in which pseudopregnancy was induced) and male rats. Studies were performed in rats of the Munich-Wistar and Sprague-Dawley strains. In micropuncture studies under anesthesia, no differences were seen in plasma volumes or whole kidney or glomerular hemodynamics in PRL-injected rats compared to those sham-injected controls regardless of sex. In separate studies, observations were made in conscious, chronically catheterized female rats of the Sprague-Dawley strain. Neither the glomerular filtration rate nor the renal plasma flow rate was different on day 9 of PRL-induced pseudopregnancy compared to values in the control state in the same animals. Thus, PRL-induced pseudopregnancy does not cause increases in glomerular filtration rate, renal plasma flow rate, or single nephron GFR or its determinants, whereas in previous studies on pseudopregnancy resulting from a sterile mating, increases in glomerular and renal hemodynamics occurred which were indistinguishable from those seen during the first half of pregnancy in the rat. These data suggest that PRL is not involved directly in either the plasma volume expansion or increase in renal hemodynamics that occurs after mating in the rat.