Growth hormone and insulin-like growth factor-I measurements in high growth (hg) mice.
Effects of a recessive gene causing high growth (hg) were studied on two major components of the growth axis in mice. Plasma and pituitary levels of growth hormone and plasma levels of insulin-like growth factor I (IGF-I) were measured in three lines homozygous for hg, each compared with a control line of alike genetic background but wild type for the hg locus (Hg). Line Gh (hghg) and line GH (HgHg) are from a line which had undergone long-term selection for high postweaning weight gain; line Ch (hghg) and line CH (HgHg) were extracted from the second backcross of Gh to C57BL/6J; line L54 (hghg) was from the sixth backcross to C57BL/6J (B6) (HgHg). Pituitary GH levels and plasma IGF-I levels were measured in both sexes at 3, 4.5, 6 and 9 wk of age. Plasma growth hormone was measured in 8- to 12-wk-old males at hourly intervals from 08.00 to 17.00. Body weight in lines homozygous for hg at 6 and 9 wk of age was 10-30% greater than in control lines. The ontogeny of this increased growth depended on genetic background. Pituitary growth hormone content was 52% lower in the two hghg lines measured (lines Ch and Gh) than in control lines at 4.5, 6 and 9 wk. Plasma growth hormone levels were also much lower in hg mice, with values only 20-30% of those in their respective controls. hg lines showed consistently low plasma growth hormone levels throughout the 9 hr sampling period, while control lines expressed the characteristic pulsatile hormone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)
Medrano
J F
JF
Department of Animal Science, University of California, Davis 95616-8521.
Pomp
D
D
Sharrow
L
L
Bradford
G E
GE
Downs
T R
TR
Frohman
L A
LA
D000818:Animals; D001835:Body Weight / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D005808:Genes, Recessive; D006128:Growth / Q000235:genetics*; D013006:Growth Hormone / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008297:Male; D051379:Mice; D010902:Pituitary Gland / Q000378:metabolism; D013223:Statistics as Topic
D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone