Mechanism of Action of Luteinizing Hormone

Abstract

THE mechanism by which luteinizing hormone stimulates the synthesis of ovarian steroid hormones is the subject of controversy. McKerns¹ has proposed that a primary action of this gonadotrophin in rat lutein and bovine corpus luteum cells is to raise the rate of production of reduced nicotinamide–adenine dinucleotide phosphate (NADPH) by a direct stimulation of glucose-6-phosphate dehydrogenase. Savard et al.² have concluded that luteinizing hormone stimulates steroid production by an effect on protein synthesis following an increase in the intracellular concentration of cyclic-3′, 5′-adenosine monophosphate. If luteinizing hormone acts by increasing the rate of production of NADPH by glucose-6-phosphate dehydrogenase (or some other cytoplasmic NADP-linked dehydrogenase) it should be possible to demonstrate a rise in the tissue concentration of NADPH when steroid synthesis is stimulated. We have made parallel measurements of the concentrations of oxidized and reduced pyridine nucleotides, and the rates of steroid synthesis in lutein tissue taken from rats before and after treatment with luteinizing hormone.