First-pass hepatic extraction and metabolic effects of insulin and insulin analogues.

First-pass hepatic extraction of insulin and hepatic and peripheral contributions to hypoglycemia were compared in conscious dogs during portal infusion of insulin A1, B29 diacetyl insulin, or A1-B29 dodecoyl insulin at 7 and 14 pmol X kg-1 X min-1. The liver removed 43 +/- 2% of insulin, 12 +/- 1% of dodecoyl, and 8 +/- 1% of diacetyl insulin, in a single transhepatic circulation. The hypoglycemia induced by insulin and diacetyl insulin and the ensuing glucagon response were greater than that produced by the dodecoyl analogue. Diacetyl insulin primarily increased glucose utilization, dodecoyl insulin solely inhibited hepatic production, and insulin affected both. The lack of hepatic effect of diacetyl insulin during hypoglycemia can be ascribed to greater counterregulation, because under euglycemic clamp conditions, this analogue caused suppression of glucose production. The different patterns of hypoglycemia exhibited can be explained by the combined effects of altered distribution between the liver and peripheral tissues caused by differences in hepatic extraction, the effect of this phenomenon on the counterregulatory response, and the intrinsic biological potency of the analogues.