Insulin-like growth factor-I, insulin-like growth factor-binding proteins, and gonadotropins in the hypothalamic-pituitary axis and serum of nutrient-restricted ewes.
Body condition scores (BCS) of ovariectomized estradiol-treated ewes were controlled to examine effects of suboptimum BCS on insulin-like growth factor (IGF)-I, IGF-binding proteins (IGFBPs), and LH in the anterior pituitary gland, hypophyseal stalk-median eminence (SME), and circulation. Serum LH increased in ewes with BCS (1 = emaciated, 9 = obese) > 3 (HIGH-BCS), but not in ewes with BCS </= 3 (LOW-BCS), after onset of the breeding season. Concentrations of LH and LHbeta subunits in anterior pituitary glands were lower in LOW-BCS than in HIGH-BCS ewes. Serum IGF-I was lower in LOW-BCS than in HIGH-BCS ewes but did not differ in SME or anterior pituitary glands. In serum, the 44-kDa IGFBP-3 and 24-kDa IGFBP-4 were lower in LOW-BCS than in HIGH-BCS ewes. In anterior pituitary glands, IGFBP-2 tended to be higher in LOW-BCS than in HIGH-BCS ewes. In the SME, IGFBP-2, -3, and -5 were lower in LOW-BCS than in HIGH-BCS ewes. Low body condition may inhibit the increased secretion of LH associated with the onset of the breeding season by altering relative amounts of IGFBPs within the hypothalamic-pituitary axis.
Snyder
J L
JL
University of Wyoming, Department of Animal Science, Laramie, Wyoming 82071, USA.
Clapper
J A
JA
Roberts
A J
AJ
Sanson
D W
DW
Hamernik
D L
DL
Moss
G E
GE
D000818:Animals; D001823:Body Composition; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005508:Food Deprivation; D007031:Hypothalamus / Q000378:metabolism*; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000378:metabolism; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D008473:Median Eminence / Q000378:metabolism; D010052:Ovariectomy; D010902:Pituitary Gland / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D012756:Sheep / Q000502:physiology*
D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018975:Insulin-Like Growth Factor Binding Protein 5; D018969:Insulin-Like Growth Factor Binding Proteins; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone