Gene expression of hypothalamic growth hormone (GH)-releasing hormone and somatostatin does not correlate with pulsatile secretion of GH in the adult mouse.

The secretion of growth hormone (GH) shows a pulsatile pattern in many mammalian species, and depends on the interaction of two hypothalamic hormones, GH-releasing hormone (GHRH) and somatostatin (SRIH). A surge of GHRH secretion into the hypophysial portal blood induces peak secretion of GH from the anterior pituitary. To study whether the rhythmic and reciprocal oscillation in secretion of GHRH and SRIH are associated with changes in synthesis of these peptides, we examined the expression of hypothalamic GHRH and SRIH mRNA by Northern blotting during trough and peak phases of GH secretion in male mice. Hypothalamic GHRH and SRIH mRNA levels did not differ between trough and peak phases of GH secretion. This result suggests that changes in GHRH and SRIH secretion have little association with changes in the synthesis of these peptides at the hypothalamus in the male mouse.