Seasonal changes in testicular contents of testosterone and androstenedione and in the metabolic clearance rate of testosterone in the sand rat (Psammomys obesus)

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Abstract
Adult male sand rats (P. obesus) were caught in the Beni-Abbes area [Algeria]. The highest testicular contents of androgens (ng/testis) were observed in autumn and in winter (testosterone: 7.6 .+-. 1.1; androstenedione: 0.76 .+-. 0.11) and the lowest in early summer (June) (testosterone: 1.5 .+-. 0.3; androstenedione: 0.20 .+-. 0.05). Values had increased by late July. Annual variations of the testosterone metabolic clearance rate (l per 24 h per 100 g body wt) were similar to those of testicular androgens; values were high in winter (6.7 .+-. 0.7) and lowest in June (3.2 .+-. 0.3). The onset of testicular endocrine activity in sand rats was concomitant both with the highest temperatures and the start of reduction in photoperiod; its regression occurred when temperature and photoperiod were increasing.