Anesthesia rapidly suppresses insulin pulse mass but enhances the orderliness of insulin secretory process.

Induction of anesthesia is accompanied by modest hyperglycemia and a decreased plasma insulin concentration. Most insulin is secreted in discrete pulses occurring at approximately 6- to 8-min intervals. We sought to test the hypothesis that anesthesia inhibits insulin release by disrupting pulsatile insulin secretion in a canine model by use of direct portal vein sampling. We report that induction of anesthesia causes an abrupt decrease in the insulin secretion rate (1.1 +/- 0.2 vs. 0.7 +/- 0.1 pmol. kg(-1). min(-1), P < 0.05) by suppressing insulin pulse mass (630 +/- 121 vs. 270 +/- 31 pmol, P < 0.01). Anesthesia also elicited an approximately 30% higher increase in insulin pulse frequency (P < 0.01) and more orderly insulin concentration profiles (P < 0.01). These effects were evoked by either sodium thiamylal or nitrous oxide and isoflurane. In conclusion, anesthesia represses insulin secretion through the mechanism of a twofold blunting of pulse mass despite an increase in orderly pulse frequency. These data thus unveil independent amplitude and frequency controls of beta-cells' secretory activity in vivo.

Measurement of insulin pulsatility by sampling directly from the portal vein: a surgical model for placement of long-term prehepatic vascular sampling catheters.

A practical and repeatable method for measurement of pulsatile insulin release in the dog was developed by direct, chronic cannulation of the portal vein cephalad to the pancrease and the entry point of the cranial pancreaticoduodenal vein, with subsequent exteriorization of the sampling catheter. Mixed breed male dogs of various body weights and ages underwent midline laparotomy for exposure of the portal vein system. After exposure the portal vein was dissected free and cannulated through a purse-string suture placed just caudad (approximately 1 cm) to the entry point of the cranial pancreaticoduodenal vein with a cuffed, medical grade, silastic catheter. The catheter was advanced cranial to a point just distal to the level of the liver and secured in place via the purse-string suture and a single stay suture. The catheter was then passed through the dorsolateral abdominal wall and routed subcutaneously to a point between the shoulder blades. After catheter plug attachment the catheter was tested for patency, flushed, heparin locked, then was secured to the subcutaneous tissue between the scapulas. The dorsal skin wound and abdominal incision were closed in a routine manner, and the dogs recovered from anesthesia. Catheter patency and function in all dogs were maintained for periods up to 4 weeks. No postoperative complications such as catheter tract infections occurred, maintenance was minimal, and all dogs were afforded complete freedom of movement and activity throughout the study, with no requirement for cumbersome jackets or wraps.