Comparison of Rat and Chicken Luteinizing Hormone-Releasing Factors*

Rat and chicken luteinizing hormone- releasing factors (LRF) were partially purified and their behavior on chromatographic columns was compared. Extracts of hypothalami were purified by ultrafiltration and chromatography on Sephadex G-25 and CM-Sephadex C-25. Columns were monitored by optical density (254 mμ) and vasopressor assay. LRF activity was evaluated by release of luteinizing hormone (LH) from rat adenohypophyses in vitro, and LH was assayed by radioimmunoassay. The elution patterns of rat and chicken LRF were not distinguishable on Sephadex (Rfs 1.89–2.09), but were clearly different on the ion-exchange column. Whereas chicken LRF repeatedly emerged from 1 × 7 cm CM-Sephadex columns at tubes 10–20, rat LRF emerged from identical columns at tubes 31–40. When rat and chicken LRF fractions from Sephadex were mixed, then run on CM-Sephadex there were two distinct and separate areas of LRF activity at tubes 13–22 and 30–43. It appears that rat and chicken LRF are chemically distinct compounds although there is overlap in their biological activity. (Endocrinology89: 1460, 1971)