DISSOCIATION OF EFFECTS OF SOMATOSTATIN ANTISERUM ON GROWTH-HORMONE AND INSULIN-SECRETION

Growth hormone (GH) secretion in the rat is governed by an endogenous ultradian rhythm with major episodes of GH secretion occurring at approximately 3,3-hr intervals throughout a 24-hr period. Plasma GH concentrations reach levels of 400-800 ng/ml during a secretory burst and fall to undetectable levels (< 1 ng/ml) during trough periods.1 We have recently reported that the rGH secretory episodes are markedly suppressed in response to prolonged food deprivation.2 However, the mechanism of this suppression is unknown. Furthermore, the mechanism mediating the well-known suppression response of plasma insulin to starvation3 remains to be firmly established. Somatostatin, a tetradecapeptide originally isolated from sheep hypothalami on the basis of its ability to inhibit GH release from rat anterior pituitary cells,4 has subsequently been shown to be a potent inhibitor of both GH5-8 and insulin9-12 release in a wide variety of species. If the starvation-induced suppression of plasma GH and insulin levels is due to circulating somatostatin, we hypothesized that its effects might be neutralized or blocked by the administration of a specific antiserum to somatostatin. The aim of the experiments described in this report was to assess the role of somatostatin in mediating the inhibitory effects on GH and insulin observed during starvation. © 1978.