Qualitative and quantitative changes in plasma luteinizing hormone (LH) under stimulation by intravenous infusion of synthetic luteinizing hormone-releasing hormone (LHRH) in Japanese monkeys (Macaca fuscata) as assessed by electrofocusing.

Abstract

Using 5 adult Japanese monkeys (Macaca fuscata) of both sexes, the qualitative and quantitative changes in plasma LH caused by LHRH administration were examined before and after castration. Five hundred micrograms synthetic LHRH was infused for 2 hrs and blood samples were obtained every 15 min for 5 hrs under ketamine hydrochloride anesthesia. Plasma LH levels were determined by an in vitro bioassay using the mouse testis interstitial cell preparation. The LHRH infusion induced a biphasic release of LH in intact animals of both sexes and in castrated females but not in castrated males. The biphasic pattern of LH release was characterized by an initial acute rise followed by a plateau or a fall and the consecutive second rise after a long latent period. Aliquots of plasma samples obtained during 30-90 (corresponding to the initial rise) and 120-210 min (corresponding to the second rise) after the initiation of LHRH infusion were pooled separately (plasma pools I and II, respectively) and subjected to isoelectrofocusing (IEF) fractionation. The IEF fractionation was performed in ampholine-sucrose gradient, pH range 3.5-10, under a constant electrical power supply (3 W, 700 V) for 48 hrs at 4 degrees C. After the completion of the IEF fractionation the LH activity in each fraction was measured by the in vitro bioassay. The IEF fractionation separated plasma LH into 6 distinct species in terms of pI values. When the IEF profiles of plasma pools I and II in intact animals of both sexes were compared, the increase and the decrease in acidic to neutral LH and alkaline LH, respectively, were consistent and significant in plasma pool II. Changes of the same kind were further exaggerated when the IEF profiles in castrated animals were compared with those in non-castrated ones. The acidic LH may represent the LH species newly synthesized and not well processed. The LH species possessing pI values of 7.5-8.5 is likely to be the mature type of LH exhibiting high biological potency. The LH species migrating in the high alkaline region seems to be the LH of over-maturation.