title: Modulation of growth hormone pulsatility by sex steroids in female goats.
abstract: GH is secreted in a pulsatile manner, the pattern of which plays an important role in the regulation of growth and metabolism. Sex steroids are also known to participate in metabolic regulation. The present study was undertaken to elucidate the relationship between changes in GH pulsatility and metabolic transition during the estrous cycle in goats. From ovariectomized (OVX) and intact females in the early luteal, late luteal, and follicular phases, blood samples were taken every 15 min for 24 h, and plasma GH was measured by RIA. In the early luteal phase, GH was secreted in a distinct pulsatile manner, the pattern of which was similar to that in OVX goats, whereas the GH pulse frequency, amplitude, and area under the curve (AUC) were decreased in the late luteal phase. In the follicular phase, the GH pulse frequency, amplitude, and AUC were significantly larger than those in the late luteal phase. The regularity of GH pulsatility was highest and lowest in the early and late luteal phases, respectively. Both IGF-I and free fatty acid levels in the plasma were higher in the follicular than the luteal phase. Subcutaneous injection of estradiol to OVX goats increased the GH pulse amplitude and AUC, whereas the implantation of progesterone for 5 d decreased those parameters. These results suggest that the pulsatile pattern of GH secretion in goats varies with sex steroid levels and thereby affects IGF-I secretion and lipolysis during the estrous cycle.
authors.affiliation: Department of Veterinary Physiology and Animal Resource Science Center, Veterinary Medical Science, The University of Tokyo, Tokyo 113-8657, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yonezawa
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mogi
authors.forename: Jun You
authors.initials: JY
authors.lastname: Li
authors.forename: Ryuji
authors.initials: R
authors.lastname: Sako
authors.forename: Keitaro
authors.initials: K
authors.lastname: Yamanouchi
authors.forename: Masugi
authors.initials: M
authors.lastname: Nishihara
mesh_terms: D000818:Animals; D004967:Estrogens / Q000097:blood* / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005498:Follicular Phase / Q000187:drug effects / Q000502:physiology*; D006041:Goats; D013006:Growth Hormone / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008183:Luteal Phase / Q000187:drug effects / Q000502:physiology*; D010052:Ovariectomy; D011374:Progesterone / Q000097:blood* / Q000494:pharmacology; D011673:Pulsatile Flow / Q000187:drug effects / Q000502:physiology
chemical_list: D004967:Estrogens; D005230:Fatty Acids, Nonesterified; D011374:Progesterone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone