Serum testosterone concentrations have been determined during the menstrual cycle and early pregnancy in the bonnet monkey, Macace rediata. During the cycle, there is an increase around the time of ovulation and a secondary peak in the late luteal phase. In pregnancy, there is a distinct peak around 23-25 days, a period which corresponds to the peak of chorionic gonadotropin reported by Atkinson et al. (1975) in Rhesus monkeys. Administration of exogenous hCG causes a significant rise in the serum testosterone level in cycling monkeys.
Summary The effect of chronic infusion of gonadotropic hormone agonist Buserelin or antagonist CDB 2085 A for 15 weeks via alzet minipumps in adult male bonnet monkeys was studied. Infusion of Buserelin resulted in a decrease in the difference between serum testosterone values at 22.00 hours and 10.00 hours, decrease in responsiveness to injected Buserelin as judged by change in serum testosterone values from pre‐injection values and decrease in sperm counts. Infusion of antagonist resulted in a decrease in the difference between serum testosterone values at 22.00 hours and 10.00 hours.
Zusammenfassung Unter Verwendung von osmotischen Minipumpen wurde der Einfluß einer Dauerinfusion des GnRH‐Agonisten Buserelin bzw. des Antagonisten CDB 2085 über einen Zeitraum von 15 Wochen bei geschlechtsreifen Hutaffen untersucht. Dabei ergab sich, daß 15 Wochen nach Behandlung mit Buserelin nahezu kein Unterschied mehr zwischen dem Testosterongehalt um 10 Uhr und um 22 Uhr zu verzeichnen war. Auch nahm die individuelle Ansprechbarkeit auf Buserelin während dieser Zeit ab, d. h. nach anfänglichem Anstieg von Testosteron nach täglicher Gabe von Buserelin war dieser Effekt nach 15 Wochen nicht mehr nachweisbar. Gleichzeitig kam es unter der Therapie zu einer Abnahme der Spermatozoendichte. Auch die Infusion des Antagonisten zeigte keinen signifikanten Unterschied zwischen dem Testosteronwert um 10 Uhr und um 22 Uhr.
Administration of human chorionic gonadotropin to pregnant bonnet monkeys (Macaca radiata) at 55-60 days and 130-140 days of pregnancy resulted in a significant increase in serum progesterone levels. This effect could be observed even in lutectomized monkeys. However, no significant change in the serum estrogen level was noticed. These results suggest that although no chorionic gonadotropin is detectable in the serum after 35 days of pregnancy, the foetoplacental steroidogenic system is still responsive to exogenous gonadotropic stimulation.
Summary. The effect of injecting agonistic and antagonistic analogues of gonadotropin releasing hormone analogues on serum testosterone levels was checked in adult and immature male bonnet monkeys. Of the agonistic analogues Buserelin, Ovurelin and D‐Phe6 Gln8 GnRH were found to be most potent in increasing serum testosterone levels in the adult male bonnet monkeys. While 27‐month‐old monkeys responded well to des Gly10 GnRH, only marginal response was observed in the case of 15‐month‐old monkeys. Studies carried out with Ovurelin indicated that it was not effective in causing desensitization in adult monkeys. The antagonistic analogue was effective in blocking nocturnal surge of serum testosterone. Based on these studies it is suggested the adult male bonnet monkeys can be effectively used for testing the activity of GnRH analogues.
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