Hypothalamic regulation of impaired growth hormone secretion in diabetic rats. 2. Studies in spontaneously diabetic BB Worcester rats.

Abstract

In the present study we investigated the effects of modulating endogenous somatostatin (SRIF) on the GH response to growth hormone-releasing hormone (GHRH) in spontaneously diabetic BB/Wor rats and nondiabetic littermates. Plasma growth hormone (GH) concentrations following injection of GHRH (500 ng/kg, i.v.) were measured in the rats after pretreatment with either normal sheep serum+saline (NSS+SAL), somatostatin antibody (SRIF-Ab), or pyridostigmine bromide (PD), an acetylcholine esterase inhibitor hypothesized to decrease hypothalamic SRIF tone. The GH response to GHRH in spontaneous diabetic rats pretreated with NSS+SAL was significantly lower (p less than 0.05) than the response observed in the nondiabetic group. SRIF-Ab pretreatment reversed the blunted GH response observed in the diabetic rats. However, PD pretreatment was not effective. These results indicate that the blunted GH response observed in BB/Wor diabetic rats is reversed by neutralization of endogenous SRIF with SRIF-Ab and leads to the conclusion that SRIF plays an active role in modulating GH secretion in spontaneously diabetic rats. The failure of PD to modulate the GH response suggests this acetylcholine agonist is ineffective in this animal paradigm.