Determinations of redox states in A2 and B-cell rich islet specimens from guinea pigs, using bioluminescence assay of NAD+ and NADH

Abstract

The ability of the pancreatic islets to form ATP is often studied and this draws attention to the oxidation of NADH in the respiratory chain. It is essential to obtain data on NADP in the islet cells. The concentrations of NAD+ and NADH were determined in collagenase isolated B- and A2-cell rich pancreatic islets from normal and streptozotocin-injected guinea pigs. The measurements were performed either in islets freshly isolated or cultured after isolation. Recent improvements in bioluminescence assay made it possible to carry out a sufficient number of determinations for calculating total nucleotide concentrations and their redox states. In both kinds of islet specimens the total nucleotide concentrations were significantly higher when the cells had been cultured for 7 days after isolation. After culture the redox state as reflected by the ratio [NAD+]/[NADH] reached high values in both the A2- and B-cell rich specimens which may signify a strong capacity for drawing energy from NADH in the oxidative phosphorylation. Low values were found soon after isolation, probably indicating a state of hypoxia. The ratio [NAD+]/[NADH] appears to be a sensitive measure of the metabolic state of the cells. The 2 kinds of islet specimens displayed remarkable similarities, but it remains to be clarified whether the B-cells can change their redox state faster than the A2-cells.