Gender Difference in P Factor ( GRF ) Receptor ituitary Growth Gene Expression Hormone - Rel in the Rat easing

GH-releasing factor (GRF) is the hypothalamic peptide that stimulates both synthesis and secretion of GH. The GRF signal is transduced to somatotroph cells through pituitary GRF receptors and generates episodic bursts of GH secretion into the bloodstream. Secretion of GH is highly sexually dimorphic, particularly in the rat [1]. In female rats, GH surges are of lower amplitude and occur more irregularly and frequently, whereas GH troughs are higher than those in male rats. GRF appears to play a critical role in sexual dimorphism in GH secretion, because pulsatile GH secretion does not occur in the absence of GRF in either male or female rats [2, 3]. We here report the first evidence of marked sexual dimorphoism in pituitary GRF receptor gene expression in the rat. To determine the functional significance of this finding, we also examined how gender difference affects the ability to release GRF, an endogenous ligand for GRF receptors.