Effects of total parenteral nutrition on luteinizing hormone dynamics in the male rat

During severe nutritional deficiency, secretion of luteinizing hormone (LH) from the pituitary and testosterone from the testes are reduced, suggesting that adequate nutrient intake is important in maintaining normal plasma concentrations of reproductive hormones. A model system that employs controlled delivery of chemically defined diets and is low in stress would be helpful in studying the role of nutrients in the maintenance of the reproductive endocrine integrity. The procedures of the rat total parenteral nutrition (TPN) model previously developed by others were modified to help reduce the stress associated with the surgery and restraint necessary to provide nutrients by direct infusion into the veins. Plasma and urine LH concentrations were studied in adult male rats maintained by TPN 4-6 d. Rats fed by TPN and control rats had near equal body weight gains, plasma LH concentrations and LH responses to luteinizing hormone-releasing hormone (LHRH) after 6 d of study. LH excretion was significantly greater during infusions of TPN than during pre- or post-infusion periods (P less than or equal to 0.001), but this hypergonadotropinuria appeared to be related to the increased urine output rather than the TPN. These results indicate that the rat TPN model may be useful in the further study of nutritional involvement in reproductive processes.