Effects of insulin-like growth factor-I peptides in rats with acute renal failure.

The effect of insulin-like growth factor-I (IGF-I) administration on body weight gain and the rate of recovery of renal function was investigated in rats following an acute episode of renal ischaemia. Since the des(1-3)IGF-I and LR3IGF-I variant forms of IGF-I have been shown to be more potent than IGF-I, their effects were also examined. Acute renal failure was produced in male Sprague-Dawley rats by clamping both renal arteries for 45 min. Treatment was commenced at the time of renal artery occlusion with vehicle (0.1 mol acetic acid/l; control group), IGF-I (2.0 mg/kg per day), des(1-3)IGF-I (2.0 mg/kg per day) or LR3IGF-I (1.5 mg/kg per day) by s.c. osmotic pump, and continued for 7 days, with rats being held in metabolism cages. Glomerular filtration rate (GFR) was estimated by the use of 51Cr-EDTA continuously infused i.p. via osmotic pump. Following the episode of renal ischaemia, body weight gain and nitrogen retention were significantly improved in all three peptide-treated groups, and serum urea concentrations were reduced in the groups treated with IGF-I and des(1-3)IGF-I. However, there was no evidence of the variants having any increased potency over the growth effects of IGF-I itself. GFR was significantly reduced, urine output was increased and urinary concentrating ability was reduced in all groups compared with normal rats, with no significant effect of the IGF peptides being apparent. A closer examination of the acute effects of LR3IGF-I on renal function was undertaken by measuring GFR for 3 days before and 3 days after renal ischaemia in two groups of rats, treated for the latter 3 days with either vehicle (controls) or LR3IGF-I (1.5 mg/kg per day). LR3IGF-I treatment following renal ischaemia resulted in a significantly greater fall in GFR than in controls, urinary osmolality was also significantly reduced, and fractional excretion of sodium was increased. In addition, there was histological evidence of a greater degree of tubular epithelial calcification in the kidneys of the rats treated with LR3IGF-I. This study showed that administration of IGF peptides at doses sufficient to cause significant improvement in anabolic status did not improve renal function in rats following an acute episode of renal ischaemia. Indeed the LR3IGF-I variant of IGF-I had a deleterious effect on renal function in the early stage of the recovery period.