title: Interrelationships between plasma insulin-like growth factor-I (IGF-I) concentrations and plasma sex hormone levels in the growing male guinea-pig.
abstract: The aim of the present study was to determine the influence of androgens on Insulin-like Growth Factor-I (IGF-I) release at puberty in male guinea-pigs. After the animals were orchiectomised (CX) or sham-operated (SO) at the end of weaning, plasma testosterone (T), dihydrotestosterone (DHT) and IGF-I levels were measured by RIA at the 4th (W4), 8th (W8) and 12th (W12) week after delivery. Body weight (BW) was recorded before sampling at each stage of the experiment. Body growth was maximal between W4 and W8 for both SO (+97%) and CX (+84%). However SO were heavier than CX at W8 and W12. In SO, a surge of plasma IGF-I levels was observed between W4 and W8, concomitantly to the increase of androgen levels (IGF-I: +86%, P less than 0.01; T: +190%, P less than 0.001; DHT: +18%; P less than 0.01). Significant correlations between IGF-I, T, DHT and BW were found only from W4 to W8 but not from W8 to W12. In CX, IGF-I levels were higher than in SO at W4 (+72%, P less than 0.01) and at W12 (+39%, P less than 0.01). A surge of IGF-I levels (+47%, P less than 0.01) was also observed but was delayed compared to SO (between W8 and W12 vs W4 and W8). BW and IGF-I levels were significantly correlated during this period. Because the surge of IGF-I levels may occur even in absence of gonads, these results give evidence that the increases in IGF-I and androgens at puberty were independent in guinea-pigs during this period.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Laboratoire de Physiologie-Biologie due Sport, Faculté de Médecine, Université d'Auvergne, Clermont-Ferrand, France.
authors.forename: B
authors.initials: B
authors.lastname: Beaune
authors.forename: N
authors.initials: N
authors.lastname: Fellmann
authors.forename: M
authors.initials: M
authors.lastname: Delaître
authors.forename: J
authors.initials: J
authors.lastname: Coudert
mesh_terms: D000375:Aging / Q000097:blood*; D000818:Animals; D001835:Body Weight; D013196:Dihydrotestosterone / Q000097:blood*; D006168:Guinea Pigs; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D009919:Orchiectomy; D009994:Osmolar Concentration; D012727:Sex Characteristics; D013739:Testosterone / Q000097:blood*
chemical_list: D013196:Dihydrotestosterone; D013739:Testosterone; D007334:Insulin-Like Growth Factor I