Differential Responses of Circulating Prolactin, GH, and ACTH Levels and Distribution and Activity of Submaxillary Lymph Node Lymphocytes to Calorie Restriction in Male Lewis and Wistar Rats

Abstract

Objectives: Calorie restriction has been associated with anorexia in growing individuals, but the mechanisms involved are not known. Also, the effects of carbohydrates and lipid restriction in growing individuals were not studied. The aim of this study was to determine whether 66% calorie restriction (lipids and carbohydrates) differentially affects growing rats of the Wistar or Lewis strains. Methods: Growing male Wistar and Lewis rats were subjected to 66% calorie restriction for 4 weeks. Plasma prolactin, growth hormone (GH), and adrenocorticotropic hormone (ACTH) levels were measured by specific radioimmunoassays. Likewise, lymphocytes from submaxillary lymph nodes were aseptically obtained to study absolute number of lymphocytes, cell surface markers (CD4+, CD8+, CD4+CD8+, B, and T cells), and proliferation. Results: The body weight gain was lower in Lewis than in Wistar rats and was blunted in both strains by calorie restriction. Wistar and Lewis rats exhibited differential patterns of plasma prolactin, ACTH, and GH levels as well as proliferative capacities of T and B cells and their distribution in the submaxillary lymph nodes. Calorie restriction increased plasma prolactin and ACTH levels in Lewis as compared with Wistar rats. However, the plasma GH levels were diminished in both strains of rats by calorie restriction. All changes in plasma prolactin ACTH and GH levels seemed to correlate with the modifications observed in the distributions of T and B subsets in the submaxillary lymph nodes as well as in their proliferative capacity. Conclusions: Calorie restriction differentially modifies the secretory patterns of prolactin, GH, and ACTH in Lewis and in Wistar rats. These changes may explain, at least in part, the associated modifications in the proliferative capacity of submaxillary lymph node lymphocytes and in their distribution.

Effects of Every-Other-Day Feeding on Prolactin Regulatory Mechanism in Transgenic Human Growth Hormone Mice

“…Previous studies in rats have shown that changes in the feeding pattern can alter plasma prolactin levels (32,33). Interestingly, plasma ACTH levels increase with variations in the feeding pattern so that the metabolic stress is activating the adrenal gland (33)(34)(35). The chronically increased corticosterone levels in GH Tg mice (36,37) may be responsible, at least in part, for the increases in TH gene expression, in agreement with earlier reports (28,38).…”

“…However, the Tg animals were apparently more sensitive to this feeding regimen, as both TH and D2LR gene expression in Tg, but not in WT mice showed a non-significant tendency to be higher in the EOD than in the control group. Previous studies in rats have shown that changes in the feeding pattern can alter plasma prolactin levels (32,33). Interestingly, plasma ACTH levels increase with variations in the feeding pattern so that the metabolic stress is activating the adrenal gland (33)(34)(35).…”