Purification and<i>in Vivo</i>and<i>in Vitro</i>Studies with Porcine Luteinizing Hormone-Releasing Factor (LRF)

Abstract

Luteinizing hormone-releasing factor (LRF) activity in acetic acid extracts of hypothalamic tissue of porcine origin was concentrated by a precipitation-extraction procedure and then subjected to purification by several successive techniques. The purification procedure consisted of gel filtration on Sephadex G-25, concentration and desalting by phenol extraction, chromatography and rechromatography on carboxymethylcellulose and column electrophoresis. LRF activity was measured by elevation of plasma luteinizing hormone (LH) in ovariectomized rats pretreated with estrogen and progesterone. Some LRF fractions were also tested by measuring depletion of ovarian ascorbic acid in pseudopregnant rats, and release of LH from rat pituitary tissue in vitro. Purified LRF was active in vivo at the level of 0.0025–0.005 μg and in vitro at the dose of 0.02 μg/pituitary. LRF was free of other known hypothalamic releasing factors and of vasopressin. Various physiological and biochemical data are presented to support the concept that LRF may be a hormone. (Endocrinology81: 77, 1967)