THE ISOLATION IN PURE FORM OF THE INTERSTITIAL CELL-STIMULATING (LUTEINIZING) HORMONE OF THE ANTERIOR LOBE OF THE PITUITARY GLAND.

Interstitial cell-stimulating (luteinizing) hormone was isolated from swine pituitary glands. This protein hormone, having a molecular weight of about 90,000 and an isoelectric point of pH 7.45, was shown to be pure by tests in the electrophoresis apparatus of Tiselius and in the ultracentrifuge as well as by its constant solubility. The hormone stimulated the interstitial tissue of the testis or ovary and caused the formation of corpora lutea provided that maturing follicles were present. Under the conditions described, its minimal effective total dose in hypophysectomized immature male rats was about 1 microgram of nitrogen or 6.7 micrograms of hormone. Extracts of swine pituitary with purely follicle-stimulating effects did not cause oestrus in immature hypophysectomized female rats unless luteinizing hormone was also administered.