A COMPARISON OF THE EFFECTS OF INSULIN-LIKE GROWTH-FACTOR-I, INSULIN AND COMBINED INFUSIONS OF INSULIN AND INSULIN-LIKE GROWTH-FACTOR-I ON GLUCOSE-METABOLISM IN DOGS

The effect of infusions of recombinant insulin-like growth factor-I (I GF-I) (34, 103 or 688 pmol kg(-1) min(-1)), insulin (3.4, 10.3 or 68.8 pmol kg(-1) min(-1)) or combined infusions (34 pmol IGF-I + 3.4 pmol kg(-1) min(-1) insulin or 103 pmol IGF-I + 3.4 pmol kg(-1) min(-1) ins ulin) on glucose metabolism was investigated in dogs using a [3-H-3]-g lucose infusion and euglycaemic clamp. All insulin doses decreased glu cose production rate (Ra) in a dose-dependent manner (P < 0.05). All I GF-I doses decreased glucose Ra (P < 0.05) but this decrease was not d ose dependent. The decrease in glucose Ra with the combined infusion o f 34 pmol kg(-1) min(-1) IGF-I + 3.4 pmol kg(-1) min(-1) insulin was g reater than 34 pmol kg(-1) min(-1) IGF-I (P < 0.05) but not different from 34 pmol kg(-1) min(-1) insulin. All insulin and IGF-I doses incre ased glucose utilization rate (Rd) in a dose-dependent manner (P < 0.0 1). The increase in glucose utilization was greater following both com bined infusions than with either component infused alone (P < 0.05). A lthough at the doses selected, insulin and IGF-I had similar effects o n glucose utilization with additive effects when the two peptides were combined, IGF-I was less effective than insulin in suppressing glucos e production.