[Diurnal and seasonal rhythms of androgen content of the plasma in Macaca mulatta].

Circadian and seasonal rhythms of testosterone-, 5 alpha-dihydrotestosterone and androstendione content were studied in the blood plasma of adult male macaca rhesus by radioimmunoassay. The circadian changes in androgen concentration depended on the seasonal and experimental conditions. Circadian variations of androgen concentration had a definite, significant character in the animals, which were previously adapted to experimental conditions. Minimum testosterone and 5 alpha-dihydrotestosterone content was noted at 18 o'clock and maximum at 21 to 24 o'clock. Circadian rhythm of androstendione content was characterized by a decrease in the evening, by a rise within the night and by the maximum value at 6 to 9 o'clock. Significant seasonal changes were observed in mean daily testosterone- and 5 alpha-dihydrotestosterone-, but hot in androstendione content. High levels of both steroids were recorded in autumn and winter, being lower in spring and the lowest in summer.