Abstract

Treatment of sheep, mice and humans with exogenous recombinantly- derived insulin-like growth factor-1 (IGF-1) has been reported to produce a hyperglycaemic state. In mice this is associated with the abolition of maternal constraint during pregnancy. Exogenous IGF-1 also alters renal clearance in sheep and humans, decreasing circulating concentrations of urea and creatinine. The objective of this study was to determine whether similar changes are apparent in sheep divergently selected for plasma IGF-1 concentrations. Ewe hoggets (10 months old), 16 each from the Massey University Low (L), Control (C) and High (H) IGF-1 selection lines, were blood sampled by jugular venipuncture over a 5 hour period after removal from pasture. Plasma metabolite concentrations were assayed and adjusted for the effects of sampling time relative to removal from pasture. There were no differences between the line (L vs C vs H) in plasma concentrations of urea (7.34 vs 7.35 vs 7.32 mM, Pooled SE = 0.25 mM) and, although there was a significant line effect for creatinine (P<0.05), none of the between-line comparisons was significant (0.073 vs 0.075 vs 0.075 mM, Pooled Se = 0.002 mM). However, glucose concentrations were greatest in the H line (3.72 mM), followed by the C line (3.56 mM) and the L line (3.45 mM) (PSE = 0.07 mM, P<0.05). Whereas glucose and urea concentrations declined with time off pasture in the H line (b = -0.133

AR, Bray, MC Smith, and NC Merrick

Proceedings of the New Zealand Society of Animal Production, Volume 53, , 323-326, 1993