Splanchnic and systemic absorption of intraperitoneal insulin using a new double-tracer method

Area of Science:

• Pharmacokinetics
• Endocrinology
• Gastroenterology

Background:

• Intraperitoneal (IP) insulin administration is a common route for managing diabetes.
• Understanding the absorption kinetics of IP insulin is crucial for optimizing therapeutic efficacy.
• Previous studies have not fully delineated the distinct splanchnic and peripheral absorption pathways.

Purpose of the Study:

• To quantitatively assess the separate absorption rates of intraperitoneal insulin into the splanchnic and peripheral circulations in dogs.
• To determine the contribution of each route to overall insulin absorption.
• To characterize the time course of intraperitoneal insulin absorption.

Main Methods:

• Utilized two distinct insulin tracers (A1-[3H]insulin and B1-[3H]insulin) infused into the superior mesenteric artery and jugular vein, respectively.
• Collected serial blood samples from the portal vein and inferior vena cava before and after IP insulin injection (1 U/kg).
• Applied simultaneous equations based on tracer principles to calculate splanchnic and peripheral absorption rates.

Main Results:

• Portal vein insulin concentrations were approximately 25% higher than inferior vena cava concentrations, indicating splanchnic absorption.
• Splanchnic absorption accounted for 51 +/- 9% of the total absorbed intraperitoneal insulin.
• Total recovery of absorbed insulin was 88 +/- 11%, with 90% absorption completion within approximately 2 hours.

Conclusions:

• Intraperitoneal insulin is rapidly and nearly completely absorbed.
• Absorption occurs via both splanchnic and peripheral routes, with roughly equal contribution.
• The findings provide valuable insights into the pharmacokinetics of intraperitoneal insulin delivery.