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Gerbils were caught in the Béni-Abbès area (Algeria). Testicular endocrine activity was highest in spring (testicular wt 298 +/- 10 mg; seminal vesicle wt 603 +/- 62 mg; testicular testosterone and androstenedione content 9.2 +/- 1.7 and 0.5 +/- 0.1 ng/testis; plasma testosterone 832 +/- 200 pg/ml). Values decreased in summer, were lowest in late summer and in autumn (84 +/- 17 mg; 40 +/- 14 mg; 0.20 +/- 0.06 and 0.02 +/- 0.01 ng/testis; 228 +/- 54 pg/ml, respectively) and increased again in winter (December-January). The onset of testicular endocrine activity was concomitant with the lowest temperatures and the shortest photoperiod; it increased when temperatures and daylength were increasing and began to decline when temperatures and photoperiod were still maximal. These seasonal changes in the endocrine activity of the testis of the gerbil differ from those of the sand rat inhabiting the same area.

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Adult male sand rats (Psammomys obesus) were caught in the Béni-Abbès area. 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 (litres/24 h/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.

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Our work aims at the exploration of cortisol secretion in the Bedouin goat, native to the Algerian Sahara desert, to understand the mechanisms of adaptation to extreme hot climates. In the present study, diurnal and seasonal variations of cortisol concentrations were measured in basal conditions, as well as the response to ACTH stimulation tests across seasons in bucks. The plasma concentrations of cortisol showed no diurnal cycle but a large variation across seasons. The highest levels occurred in summer and winter when the environmental conditions are at their extreme levels. The rectal temperature showed nychthemeral and seasonal variations, and BW was also different across seasons with highest values in summer and lowest in winter. The results obtained after administration of two doses (2 or 10 μg/kg BW) of synthetic ACTH to three different age groups (kids, adults and elderly animals) showed a strong increase in plasma cortisol concentrations under all conditions with maximum levels achieved between 15 and 120 min. The analysis of the area under the cortisol curve showed no significant difference between the responses to the two doses of ACTH and between age groups, but showed seasonal variations with the lowest response in autumn than in other seasons. We conclude that season significantly affects secretion of cortisol in both basal state and under ACTH stimulation. However, the variation of adrenal reactivity to ACTH is not sufficient to explain seasonal differences, and in particular the summer peak in basal circulating cortisol concentrations. Further research should focus on the respective contribution of environmental factors (such as day length, temperature, humidity) and the mechanisms involved in cortisol regulation.