[Demonstration of the influence of the photoperiod on the plasma concentration of the growth hormone in the ram].
The influence of photoperiod on GH release has been studied in Rams subjected to two different light regimes. The first group was submitted to natural daylight variations. The second group received daily the following split photoperiod: 7 L, 9 D, 1 L, 7 D, known to stimulate the release of prolactin. The experiment lasted 5 months, from January to June. In the first group, plasma GH concentrations decreased significantly from January to February (10.1 +/- 0.4 vs 8.7 +/- 0.3 ng X hr./ml; P less than 0.02), then increased from April to June (9.3 +/- 0.4 vs 10.5 +/- 0.7 ng X hr./ml; P less than 0.02). In the second group, GH concentrations were higher than in the first group in April (11.9 +/- 0.9 vs 9.3 +/- 0.4 ng X h/ml; P less than 0.05). However, it decreased between April and June (11.9 +/- 0.9 vs 9.7 +/- 0.4 ng X hr./ml; P less than 0.02) and then did not differ from that of the first group. These results show that plasma GH concentrations are affected by photoperiodic changes and suggest the existence of seasonal variations in GH plasma levels in the Ram.
D000818:Animals; D013006:Growth Hormone / Q000097:blood*; D008027:Light; D008297:Male; D012621:Seasons; D012756:Sheep / Q000502:physiology*
D013006:Growth Hormone
Mise en évidence de l'influence de la photopériode sur la concentration plasmatique de l'hormone de croissance chez le Bélier.