In vitro effect of hypothalamic extract and other stimulating agents on glucose oxidation and luteinizing hormone (LH) release from rat anterior pituitary glands.

Abstract

Rat hemi-pituitaries were incubated with an ovine hypothalamic stalk-median eminence extract (HE) or its ultrafiltrate (HEUF). LH release was measured by radioimmunoassay (RIA) and glucose oxidation was estimated by measuring 14CO2 derived from 14C-glucose. HEUF produced a dose-dependent LH-releasing effect, but did not alter the total amount of LH in the incubation system. The effect of HE on LH release could not be studied because of the presence of crossreactive contaminants which interfered with the RIA. Both HE and HEUF increased glucose oxidation by anterior pituitary tissue, an effect observed during the first 10 min of incubation. Iodoacetate which severely suppressed glucose oxidation increased basal release of LH and prevented any further stimulation of LH release by HEUF. 2,4-Dinitrophenol which abolished the promotion of glucose oxidation by HEUF caused an increase in the basal LH release and also blocked the LHreleasing effect of HEUF. A high potassium medium (60 HIM) which stimulated LH release also promoted glucose oxidation. Calcium-free medium abolished the effect of high potassium on LH release even though glucose oxidation was increased. Although theophylline enhanced the effect of HEUF and dibutyryl cyclic AMP on LH release, it decreased the stimulating effect of dibutyryl cAMP on glucose oxidation. The LHreleasing effect of HEUF appears to be independent from its effect on glucose oxidation. (Endocrinology90: 690, 1972)