Characterization of GH pulsatility in male Shiba goats: effects of postpubertal castration and KP102.
The present study was conducted in order to characterize the secretory pattern of GH in the Shiba goat, a native Japanese miniature goat, and to examine the effects of castration and KP102, a GH secretagogue, on this pattern. Blood samples were taken from an indwelling jugular catheter every 15 min for 24 h, and plasma GH was measured by radioimmunoassay. In intact males, GH was secreted in a pulsatile manner with very regular 5-h periodicity, which consisted of a distinctive GH pulse and a trough of virtually no GH secretion. Postpubertal castration increased the height and decreased the width of GH pulses, though it did not affect the interpulse interval and area under the curve. Modification of the shape of each GH pulse by testicular androgen might play a role in the expression of GH action in the male. KP102 (10 microg/kg, i.v.) immediately induced a robust GH pulse, which was followed by a spontaneous GH pulse of normal characteristics at regular intervals, suggesting that the clock generating GH pulses was reset by KP102. From these observations, we concluded that the Shiba goat is a very suitable experimental model for elucidating the mechanisms underlying GH pulse generation, and in particular, the involvement of androgen and GH secretagogues.
Mogi
Kazutaka
K
Department of Veterinary Physiology, Veterinary Medical Science, The University of Tokyo, Japan.
Li
Jun You
JY
Suzuki
Masatoshi
M
Sawasaki
Toru
T
Takahashi
Michio
M
Nishihara
Masugi
M
D000818:Animals; D006041:Goats / Q000502:physiology*; D013006:Growth Hormone / Q000097:blood* / Q000378:metabolism; D006728:Hormones / Q000494:pharmacology*; D008297:Male; D009842:Oligopeptides / Q000494:pharmacology*; D009919:Orchiectomy; D011673:Pulsatile Flow / Q000187:drug effects / Q000502:physiology; D012636:Secretory Rate / Q000187:drug effects / Q000502:physiology
D006728:Hormones; D009842:Oligopeptides; D013006:Growth Hormone; C091874:growth hormone-releasing peptide-2