Food restriction differentially affects pituitary hormone mRNAs throughoutthe adult life span of male F344 rats

Because neuroendocrine mechanisms may contribute to the antiaging effects o f food restriction (FR), we measured the effect of FR on mRNAs encoding ant erior pituitary (AP) tropic hormones. Slot blots or RNase protection assays were done on AP RNA from 3-, 6-, 12-, 18- and 24-mo-old male F344 rats con suming food ad libitum (AL) or food restricted (FR; to 60% of AL food intak e) from 6 wk, Both AL and FR rats gained body weight during the study (P < 0.05), but FR rats weighed similar to 40% less (P < 0.0001). Messenger RNA levels were expressed in two ways, i.e., per total AP and per microgram tot al AP RNA. Proopiomelanocortin (POMC) mRNA/mug RNA was higher (P < 0.0005) in FR than in AL rats at all ages. Thyroid-stimulating hormone (TSH) beta m RNA declined with age (P < 0.05) in AL but not FR rats and was reduced by F R up to 12 mo (P < 0.01). Growth hormone (GH) mRNA/mug RNA declined with ag e (P < 0.05) in AL but not FR rats, and total GH mRNA in the AP was reduced by FR at early ages (P < 0.05). FR reduced prolactin (PRL) mRNA and its ag e-related increase (P < 0.0005). Levels of luteinizing hormone (LH) beta an d follicle-stimulating hormone (FSH) beta mRNAs did not differ between AL a nd FR rats until 12 mo, but thereafter rose in FR (LH beta mRNA; P < 0.01, FSH beta mRNA; P < 0.05). Many of these changes in gene expression corrobor ate previously reported hormonal changes in FR rodents and mutant mice with extended life spans, and thus provide further support for the hypothesis t hat an altered hormonal milieu contributes to the antiaging effects of food restriction.