Abstract
Changes were demonstrated in isoelectric focusing (IEF) profiles of pituitary luteinizing hormone (LH) in the cynomolgus monkey during the menstrual cycle. The LH activity was determined through radioreceptorassay (RRA) and exhibited a heterogeneous IEF profile. Highly alkaline isohormones (pl ?? 8.6) were predominant in the pituitary collected from animals in the follicular phase. The IEF profile from periovulatory period animals showed a significant increase in relative amounts of lesser-alkaline (pl=8.3 and 7.5) and neutral (pl=7.0) isohormones. The IEF profile from luteal phase animals showed considerable LH activity from pH 8.3 to 9.1 with a narrow peak of LH at pH 7.5. Seven isohormone fractions (pl=7.0 to 11.5) were obtained from male monkeys. Serial dilution of the 7 isohormone fractions as well as human chorionic gonadotropin (hCG) and monkey pituitary fractions were tested in the RRA. There was a stepwise increase in the slopes of the dose-response curves with increasing pl values of the isohormones. The receptor-binding property of hCG and the highest alkaline isohormone is not affected by the presence or absence of NaCl, while the binding of cynomolgus monkey pituitary LH and other isohormones apparently decreases with the presence of NaCl. Receptor-binding properties of each LH-isohormone were analyzed.
