Effect of acute glucose antagonism on hypophyseal hormones and concentrations of insulin-like growth factor (IGF)-I and IGF-binding proteins in serum, anterior pituitary, and hypothalamus of ewes

The objectives of this study were to determine whether 2-deoxy-D-glucose (2DG), a metabolic inhibitor of glucose, 1) differentially affected release of LH, growth hormone (GH) and prolactin (PRL); 2) decreased anterior pituitary response to GnRH; and 3) altered concentrations of insulin-like growth factor I (IGF-I) and intensity of 125I-IGF-I binding to proteins (IGFBPs) in serum, anterior pituitary (AP), and hypothalamus (preoptic area [POA], medial basal hypothalamus [MBH], and stalk median eminence [SME]). In trial 1, mature, ovariectomized, crossbred ewes were treated with a single s.c. injection of either saline (n = 5) or 2DG (n = 5; 0.1 g/kg BW). Administration of 2DG suppressed (p 0.05) concentrations of LH but did not affect (p 0.05) serum concentrations of GH or PRL. In trial 2, ovarietomized ewes received injections of saline or 2DG, and each group was subdivided to receive either saline or GnRH analog (5 micrograms; Des-Gly10-[D-Ala6]) 2 h later. Administration of 2DG suppressed (p 0.05) serum concentrations of LH before administration of GnRH; however, release of LH in response to exogenous GnRH was greater (p 0.05) in ewes that received 2DG. Treatment with 2DG did not affect (p 0.05) concentrations of FSH before or after administration of GnRH. In trial 3, 10 ovariectomized ewes were slaughtered 2 h after treatment with saline (n 0.05) by treatment with 2DG. IGFBPs were detected in serum, AP, and SME of all ewes, but intensity of 125I-IGF-I binding to proteins was not affected (p 0.05) by treatment with 2DG. In summary, treatment with 2DG decreased release of LH. The suppression of LH did not appear to be caused by direct actions of 2DG on the AP