Possible mechanisms which mediate avian resistance to exogenous insulin

Cardiovascular, metabolic, and endocrine parameters were utilized to investigate insulin resistance in the domestic fowl. Cardiovascular measurements were recorded on an E&M Physiograph, and body fluid volumes were determined using dye dilution techniques. In the early phase of insulin hypoglycemia, pulse pressure increased and blood pressure decreased with tachycardia not being observed until 60 minutes after insulin injection. Mean electrical axis deviation, hematocrit, respiratory rate, plasma volume, blood volume, and thiocyanate space were found not to change during insulin hypoglycemia. For information concerning cellular metabolism, [raised 14]C-glucose and insulin (or saline) were injected and [raised 14]C-activity in plasma, liver glycogen, and blood bicarbonate were determined. Additionally, [raised 14]C-3-0-methylglucose plasma activity was recorded after insulin injection. The rate of appearance of radioactive blood bicarbonate was not increased after insulin administration indicating insulin does not augment glucose degradation to CO[lowered 2] in chickens. Sixty minutes after insulin injection no change in specific activity of liver glycogen could be detected; however, glycogenolysis occurred, therefore hepatic incorporation of was reduced. Increase in glucose space (as estimated from increased 3-0-methyl glucose space) accounted for increased removal of [raised 14]C-activity from the plasma when insulin was administered. The avian metabolic system appeared to demonstrate "insulin resistance" relative to mammalian metabolic parameters which are reported to change after insulin injection. The present study indicated the resistance to insulin was partially mediated through a response of the endocrine system. Catecholamines were selectively adsorbed onto aluminum oxide and then oxidized to a fluorescent trihydroxyindole derivative. Plasma epinephrine concentration increased after injection of insulin (chicken insulin more effective than beef insulin): epinephrine has been reported to "antagonize" insulin by encouraging hyperglycemia. Tolbutamide injection (administered in doses to give an equivalent degree of hypoglycemia to that of injected beef and chicken insulins) resulted in no detectable epinephrine release above that of control levels.Biology and Biochemistry, Department o