Insulin responsiveness of sheep, ponies, miniature pigs and camels: results of hyperinsulinemic clamps using porcine insulin

It had been suggested that marked species differences in glucose tolerance tests were due to differences in insulin resistance. To compare insulin res ponsiveness, euglycemic hyperinsulinemic clamps were carried out in sheep, ponies, miniature pigs and camels. Porcine insulin was infused as primed-co ntinuous infusions for 2 h (6 mU.kg(-1).min(-1)). The steady state glucose infusion rates in the pigs, sheep, ponies and camels were 96.0, 18.6, 7.1 a nd 6.1 mu mol.kg(-1).min(-1), respectively. The maximal plasma insulin conc entrations during the insulin infusions were 2,700 muU.ml(-1) in the camels , 1,400 muU.ml(-1) in the sheep and ponies and 600 muU.ml(-1) in the pigs. The rate of insulin removal from plasma was lowest in the camels as compare d to the sheep, ponies and pigs (0.019, 0.038, 0.035 and 0.070 min(-1) resp ectively). In all species the concentrations of plasma non-esterified fatty acids dropped significantly 10-30 min after the start of the insulin infus ion. However, the rates of non-esterified fatty acid reduction were higher in the pigs and sheep than in the camels and ponies. Results confirm a cons iderably higher insulin responsiveness in the pigs as compared to the sheep . The ponies and camels were found to be even more insulin-resistant than t he sheep.