The combined effects of dietary protein and fat on prolactin in female rats.

A 3 X 3 factorial experiment was conducted to examine how protein content (8, 16 and 32% of kcals from casein) and fat content (12, 24 and 48% of kcals from corn oil) interact to influence prolactin homeostasis in female rats. Weanling Sprague-Dawley rats were assigned to each of nine diets fed ad libitum. Dietary fat had no effect on the time of vaginal opening although first estrus occurred slightly earlier with high fat diets (P less than 0.05). Rats fed diets with protein at 8% of kcal showed a 2-wk delay in vaginal opening and first estrus. After 18-20 wk of feeding, serum and pituitary prolactin concentrations were determined after decapitation during the afternoon of proestrus or diestrus. Although serum prolactin was elevated at proestrus, there were no effects of fat or protein on the serum or pituitary prolactin. Another group of rats were fitted with jugular cannulae and treated with perphenazine, a potent prolactin-stimulating drug. Dietary fat or protein had no effect on prolactin secretion after perphenazine treatment. In the final experiment, rats fed each diet were treated with either i.p. saline or perphenazine followed by decapitation. The pituitary was removed 3 h later for determination of the amount of prolactin depleted from the pituitary. There was no effect of diet on the amount of pituitary prolactin depleted by perphenazine. No evidence was obtained that changes in dietary fat or protein concentration influence serum prolactin or its secretion in response to a provocative stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)