EFFECTS OF FOOD-DEPRIVATION ON THE GH AXIS - IMMUNOCYTOCHEMICAL AND MOLECULAR ANALYSIS

Neuroendocrine mechanisms governing growth hormone (GH) secretion are sensitive to nutritional status since the normal pulsatile pattern of GH release is disrupted during conditions of food deprivation or malnu trition. A reasonable hypothesis for this occurrence is the alteration of somatostatin and GH-releasing hormone (GHRH) synthesis, storage an d secretion. In this study, we investigated the effects of food depriv ation on GH, GHRH, hypothalamic and pituitary galanin (GAL), and somat ostatin through immunocytochemical and mRNA analysis. Adult male rats were subjected to 72 h of food deprivation, during which an average of 18% total body weight was lost. ICC studies were performed on brain s ections from the rostral, middle and caudal regions of the median emin ence of the hypothalamus using the avidin-biotin-peroxidase method. Im munocytochemical results were generated for the percent area and optic al density (intensity) of immunostaining in the median eminence. Messe nger RNA analyses were performed using sense and antisense riboprobes produced from cDNA clones for GH, GHRH, somatostatin and GAL. Food dep rivation decreased somatostatin immunostaining in middle and caudal re gions of the median eminence; similarly, food deprivation resulted in decreased GHRH immunostaining in rostral and middle sections of the me dian eminence of the hypothalamus. mRNA levels for somatostatin, GHRH and GH and GAL were also reduced by food deprivation. Our data suggest that suppressed GH secretion in food-deprived rats may reflect a gene ral downregulation of the neuroendocrine and pituitary GH axis.