Altered renal function in chronically hyperprolactinaemic rats.

1. Standard renal clearance techniques were used to investigate the effects of chronic hyperprolactinaemia on kidney function in male, female and ovariectomized female rats. 2. All hyperprolactinaemic rats showed a significantly increased glomerular filtration rate (G.F.R.) compared to controls. Values were (microliter min-1) 2738 +/- 146 vs. 2299 +/- 99 for males (P less than 0.05), 2236 +/- 79 vs. 1865 +/- 74 for females (P less than 0.01) and 2200 +/- 76 vs. 1941 +/- 62 for ovariectomized females (P less than 0.05). 3. Hyperprolactinaemic rats in all groups also showed a significant increase in absolute tubular reabsorption of water, sodium and chloride compared to their respective controls. Increases here averaged 19%. 4. There was a significantly greater fractional tubular reabsorption of fluid and solutes in hyperprolactinaemic male rats compared to controls. Values were (%) 92.9 +/- 0.6 vs. 90.3 +/- 0.7 for water, 93.0 +/- 0.4 vs. 91.0 +/- 0.6 for sodium and 89.9 +/- 0.7 vs. 86.5 +/- 0.9 for chloride. In each case P less than 0.05. 5. These results imply an osmoregulatory role for prolactin which is not specific to pregnancy or related female reproductive states.