Linked Life Data

1915083

Source:http://linkedlifedata.com/resource/pubmed/id/1915083

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1991-10-30
pubmed:abstractText
Puberty in the female lamb is accompanied by an increased frequency of LH pulses, and during normal development this is preceded by a decline in GH. Conversely, in the growth-retarded lamb, when LH levels are depressed by low nutrition, GH secretion is elevated. Based upon this inverse relationship, we tested the hypothesis that GH may act as a metabolic signal from the brain to inhibit the secretion of LH, and that the decline in GH times puberty. Our approach was to extend high circulating GH levels far beyond the early postnatal period, in a physiological pattern and level, in an attempt to block the pubertal LH rise. To evaluate the pattern of LH as a continuous variable under conditions of constant estradiol negative feedback, the gonadotropin was measured in blood samples collected by jugular venipuncture twice weekly; the lambs were ovariectomized and treated chronically with estradiol (Silastic capsule) beginning at 3 weeks of age. Nine lambs served as untreated controls, and 7 were infused iv with pituitary-derived bovine GH (bGH) between 5 and 28 weeks of age. A programmable backpack infusion pump delivered bGH as hourly pulses, with a total dose of 18 micrograms/kg.24 h, to maintain a physiological pattern and level of GH. At various ages, blood samples were collected at 12-min intervals for 6 h to monitor patterns and levels of peripheral LH and GH. Circulating GH in untreated and treated lambs averaged 7.7 +/- 1.5 ng/ml over a 6-h period at 4 weeks of age and declined to 1.1 +/- 0.2 ng/ml by 19 weeks in the untreated lambs; in contrast, bGH-infused lambs averaged 10.4 +/- 0.9 ng/ml at 19 weeks. Although body weights did not differ, back fat depth and quantity of perirenal fat were reduced in bGH-treated females compared to that in controls. Moreover, insulin-like growth factor-I levels were higher in bGH-treated compared with control lambs, and the bGH-treated lambs exhibited glucose intolerance, thus confirming that infused bGH was biologically active. Neuroendocrine sexual maturity, however, was not different in bGH-treated and control lambs, and it occurred at 21-22 weeks of age. The results do not support our hypothesis that decreasing GH secretion is a requirement for puberty in the sheep. Moreover, unlike in children with delayed puberty, exogenous bGH did not advance normal puberty in the lamb.(ABSTRACT TRUNCATED AT 400 WORDS)
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
AIM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0013-7227
pubmed:author
pubmed:issnType
Print
pubmed:volume
129
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2024-32
pubmed:dateRevised
2010-4-12
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
Metabolic interfaces between growth and reproduction. IV. Chronic pulsatile administration of growth hormone and the timing of puberty in the female sheep.
pubmed:affiliation
Reproductive Sciences Program, University of Michigan, Ann Arbor 48109.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't