Lack of effect of exogenous insulin-like growth factor-I (IGF-I) on chick embryo growth rate

International audienc

Physiological inhibition of growth hormone secretion by both insulin-like growth factors-I and -II in chickens

1. The role of both insulin-like growth factors (IGF)-I and -II in regulation of growth hormone GH) secretion in chickens was examined. Seven-week-old male broiler chickens were injected intravenously (iv) with recombinant human IGF-I or IGF-II or specific anti-IGF-I or IGF-II immunoglobulins. Blood samples were taken before treatment and at 15 min intervals afterwards for 1 h. Controls received saline iv. 2. Both IGF-I and IGF-II administration resulted in a rapid, significant decrease in plasma GH concentrations, but the concentrations of both triiodothyronine and thyroxine remained unchanged. 3. Immunisation against both IGF-I and IGF-II produced a significant elevation in plasma GH. 4. These data show that both IGFs can regulate GH concentrations in birds. Furthermore, the immunoneutralisation data suggest that these hormones have a physiological role in the regulation of GH secretion

Decreased circulating growth hormone levels following centrally administered insulin-like growth factor-1 is not mediated by somatostatin in the pig fetus

International audienc

The regulation of GH-dependent hormones and enzymes after feed restriction in dwarf and control chickens

The principal objective of this study was to examine the GH-dependency of IGF-I and IGF-II changes in the chicken. To this end, the regulation of GH-dependent hormones and enzymes were studied in undernourished normal and dwarf chickens. The dwarf chickens examined exhibit a Laron-type dwarfism and have been shown to be GH receptor deficient. Thus, they provide an interesting model to determine the GH-dependency of IGF-I and IGF-II changes. Short (1 day) and long-term (7 days) feed restriction was imposed on growing normal and dwarf chickens to follow the subsequent endocrine changes. Since short-term feed restriction of dwarf chickens resulted in decreased plasma IGF-I, it appears that this is not a GH-dependent effect. However, with longer term undernutrition, IGF-I was not decreased in dwarf chickens. So, after a longer restriction period, the regulation of these factors appears to become more GH-dependent. IGF-II was not depressed at all by feed restriction in the dwarf chicken, suggesting a degree of GH-dependency.status: publishe

Somatostatin immunoneutralization affects plasma metabolite concentrations in the domestic fowl

1. Young leghorn cockerels were injected with antiserum to somatostatin (anti-SRIF) and plasma glucose, free fatty acids and α-amino nitrogen concentrations determined. 2. Plasma glucose concentrations increased rapidly after anti-SRIF and remained high for up to 2 hr. Two different antisera tested had hyperglycaemic activity. 3. Plasma free fatty acids also increased rapidly after administration of the two different anti-SRIFs, and remained high for about 1 hr. 4. Plasma α-amino nitrogen increased during the first 30 min after anti-SRIF, then declined to levels significantly lower than control by 1–2 hr after injection. 5. Anaesthesia reduced plasma concentrations of glucose and α-amino nitrogen, and also reduced the changes of these metabolites following anti-SRIF. 6. The results show the importance of endogenous somatostatin in the regulation of plasma metabolite concentrations.link_to_subscribed_fulltex

Effects of passive immunization with antisomatostatin serum on plasma corticosterone concentrations in young domestic cockerels

Young cockerels (6-8 weeks old) were injected with serum from sheep immunized against somatostatin-14 (anti-SRIF) or normal sheep serum (NSS). Blood samples were withdrawn periodically for the determination of plasma corticosterone concentration by radioimmunoassay. With frequent (every 10 min) sampling, NSS-treated control animals exhibited increased plasma corticosterone levels, presumably as a stress response to the experimental manipulation. Anti-SRIF stimulated a much greater increase in plasma corticosterone concentrations and a peak response was observed within 10 to 20 min, when the plasma corticosterone level reached more than twice that of the corresponding control value. With less frequent sampling, plasma corticosterone increased with anti-SRIF administration to as much as nine times the corresponding control value, and the peak response occurred much later. Under pentobarbitone anaesthesia, which itself increased basal corticosterone concentrations, anti-SRIF treatment promoted further increases in plasma corticosterone levels although to a smaller magnitude compared with conscious birds. The results suggest that endogenous somatostatin may play a role in the regulation of adrenocortical function in the domestic fowl. The mechanism of response may involve a central component.link_to_subscribed_fulltex