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Effects of photoperiod on secretory patterns of growth hormone in adult male goats
Author(s) -
Jin Jin,
Sawai Ken,
Hashizume Tsutomu
Publication year - 2013
Publication title -
animal science journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.606
H-Index - 38
eISSN - 1740-0929
pISSN - 1344-3941
DOI - 10.1111/asj.12073
Subject(s) - photoperiodism , endocrinology , medicine , prolactin , testosterone (patch) , biology , secretion , growth hormone , pulsatile flow , hormone
The aim of the present study was to clarify the effect of photoperiod on secretory patterns of growth hormone ( GH ) in male goats. Adult male goats were kept at 20°C with an 8‐h or 16‐h light photoperiod, and secretory patterns of GH secretion were compared. In addition, plasma profiles of prolactin ( PRL ), insulin‐like growth factor‐ I ( IGF ‐ I ) and testosterone (T) were also examined to characterize GH secretion. GH was secreted in a pulsatile manner. There was no significant difference in pulse frequency between the 8‐h and 16‐h photoperiods. However, GH pulse amplitude tended to be greater in the group with the 16‐h photoperiod ( P = 0.1), and mean GH concentrations were significantly greater in the 16‐h photoperiod ( P < 0.05). The GH ‐releasing response to GH releasing hormone was greater in the 16‐h than 8‐h photoperiod ( P < 0.05). Plasma PRL and IGF ‐ I levels were higher in the 16‐h than 8‐h photoperiod ( P < 0.05). In contrast, plasma T levels were lower in the 16‐h photoperiod ( P < 0.05). These results show that a long light photoperiod enhances the secretion of GH as well as PRL and IGF ‐ I , but reduces plasma T concentrations in male goats.