Isolation and physicochemical characterization of luteinizing hormone from human pituitary glands.

Luteinizing hormone containing 8.9 NIH-LH-Sl units per mg was isolated from human pituitary glands by isoelectric focusing in a sucrose gradient containing carrier ampholytes. Approximately 88% of the starting units was recovered, suggesting no apparent loss or inactivation of the hormone activity during isolation procedures. The luteinizing hormone showed a single protein band in acrylamide disc electrophoresis and a single precipitin band in immunoelectrophoresis with antisera to luteinizing hormone and to human chorionic gonadotropin. The luteinizing hormone did not cross-react with antisera to follicle-stimulating hormone or to serum proteins. The hormone sedimented as a single boundary in the ultracentrifuge with an ~20,~ of 2.31 S. A Stokes radius of 28.5 A and a molecular weight of 26,750 were calculated for the luteinizing hormone. Amino acid analysis revealed a high content of proline. Serine was detected at the COOH terminus. The luteinizing hormone was devoid of follicle-stimulating hormone activity; however, it contained 0.1 USP-TSH unit per mg.