Measurement of pulsatile insulin secretion in the rat: direct sampling from the hepatic portal vein

Abstract

Matveyenko AV, Veldhuis JD, Butler PC. Measurement of pulsatile insulin secretion in the rat: direct sampling from the hepatic portal vein. Am J Physiol Endocrinol Metab 295: E569 -E574, 2008. First published June 24, 2008 doi:10.1152/ajpendo.90335.2008.-It has previously been shown that insulin is secreted in discrete secretory bursts by sampling directly from the portal vein in the dog and humans. Deficient pulsatile insulin secretion is the basis for impaired insulin secretion in type 2 diabetes. However, while novel genetically modified disease models of diabetes are being developed in rodents, no validated method for quantifying pulsatile insulin secretion has been established for rodents. To address this we 1) developed a novel rat model with chronically implanted portal vein catheters, 2) established the parameters to permit deconvolution of portal vein insulin concentrations profiles to measure insulin secretion and resolve its pulsatile components, and 3) measured total and pulsatile insulin secretion compared with that in the dog, the species in which this sampling and deconvolution approach was validated for quantifying pulsatile insulin secretion. In rats, portal vein catheter patency and function were maintained for periods up to 2-3 wk with no postoperative complications such as catheter tract infection. Rat portal vein insulin concentration profiles in the fasting state revealed distinct insulin oscillations with a periodicity of ϳ5 min and an amplitude of up to 600 pmol/l, which was remarkably similar to that in the dogs and in humans. Deconvolution analysis of portal vein insulin concentrations revealed that the majority of insulin (ϳ70%) in the rat is secreted in distinct insulin pulses occurring at ϳ5-min intervals. This model therefore permits direct accurate measurments of pulsatile insulin secretion in a relatively inexpensive animal. With increased introduction of genetically modified rat models will be an important tool in elucidating the underlying mechanisms of impaired pulsatile insulin secretion in diabetes. deconvolution; pulse mass; GLUCOSE HOMEOSTASIS DEPENDS on adequate insulin secretion. Insulin is secreted in coordinate discrete secretory bursts by the pancreatic islets of Langerhans (7,12,17). Although this pattern of insulin secretion results in relatively modest oscillations in insulin concentration in the systemic circulation, direct sampling from the portal vein in dogs and humans reveals large amplitude oscillations in insulin concentration with a periodicity of ϳ4 min (23, 30). Therefore, to evaluate pulsatile insulin secretion, it is preferable to sample directly from the portal vein. This has been accomplished in humans under exceptional circumstances (30), but in general animal models are required to investigate pulsatile insulin secretion. Because of blood volume considerations, these studies (21, 24, 25) were for the most part initially carried out in large animals such as the dog.Since anesthesia profoundly suppresses pulsatile insulin secretion (35), we developed ...

Insulin Secretion and Actions

“…In humans, mouse and rat the majority of insulin (>70%) is released in a pulsatile manner with a periodicity of 3-5 min (Matveyenko et al, 2008;Porksen et al, 1997;Song et al, 2000). This pattern is observed both before and after meals, however the amplitude of oscillation is higher during the postprandial period.…”

Adaptations in pulsatile insulin secretion, hepatic insulin clearance, and β-cell mass to age-related insulin resistance in rats

“…The surgical implantation of the portal vein and arterial sampling catheters as well as jugular vein infusion catheters has been described in detail (37). In brief, rats were anesthetized by isoflourane (2.5%) inhalation until effect.…”

“…To assess the impact of aging on fasting insulin secretion, male Sprague-Dawley rats ages 2 (n ϭ 7), 7 (n ϭ 5), and 12 (n ϭ 5) mo old were studied in the conscious unrestrained state 12 h after food withdrawal the preceding day and 5-7 days after surgery as described in detail (37). In short, rats were placed in a cage outfitted with a counter-weighted swivel mount (Instech), and, following a 30-min equilibration period (Ϫ30 to 0 min), portal vein blood (ϳ80 l) was sampled every minute for 35 min, and arterial samples (ϳ100 l) were sampled every 10 min.…”

Slow oscillations of KATP conductance in mouse pancreatic islets provide support for electrical bursting driven by metabolic oscillations

“…Under normal physiological conditions, pancreatic insulin secretion results in the appearance of pulses of plasma insulin in humans, mice, rats and dogs (28,33,36,42). Mouse islets display diverse oscillatory patterns, consisting of slow (2-7 min), fast (Ͻ2 min), or compound (fast overlapped with slow) (22,33).…”