AJP - Endocrinology and Metabolism, Vol 266, Issue 5 E750-E759, Copyright © 1994 by American Physiological Society
Splanchnic and systemic absorption of intraperitoneal insulin using a new double-tracer method
J. Radziuk, S. Pye, D. E. Seigler, J. S. Skyler, R. Offord and G. Davies
Department of Medicine, McGill University, Montreal, Quebec, Canada.
The absorption of a bolus of intraperitoneal insulin into the splanchnic
and peripheral circulations was separately assessed in dogs using an
infusion of two insulin tracers (A1-[3H]insulin and B1-[3H]insulin). One
tracer was infused into the superior mesenteric artery and the second into
the jugular vein. Serial samples were taken before and after an injection
of insulin (1 U/kg ip). Sampling was from the portal vein and the inferior
vena cava. By using the principle of equivalent entry of tracer and
unlabeled material, we developed two simultaneous equations for the rate of
splanchnic and peripheral insulin absorption at each time point. These were
solved to yield the two rates. Mean concentrations in the portal vein were
approximately 25% higher than in the inferior vena cava, reflecting the
splanchnic absorption. This rate accounted for almost half (51 +/- 9%) of
the insulin absorbed. The remainder of the absorption was peripheral. The
total recovery of intraperitoneal insulin, absorbed by either route, was 88
+/- 11%. Portal absorption peaked earlier than peripheral. Absorption by
both routes was 90% complete within approximately 2 h (131 +/- 16 min). In
summary, therefore, intraperitoneal insulin is rapidly and almost
completely absorbed, with absorption split between the splanchnic and
peripheral routes of entry.
