Metabolic Characteristics of Isolated Pancreatic Islets in Tissue Culture

Abstract

The present studies were performed to investigate the possibility of culturing isolated pancreatic islets in vitro in a system which should allow assessment of both morphologic and metabolic alterations in the islet cells after prolonged periods of incubation. For this purpose, isolated islets from adult mice were maintained in stationary organ cultures in a nutrient medium containing glucose at a concentration of either 1.2 mg./ml. or 5 mg./ml. After six or twelve days in culture, the islets were studied with regard to light-microscopic appearance, rates of oxygen consumption, glucose oxidation, insulin release and insulin content. The metabolic rates were determined in short-term incubations (30–150 minutes) so that relevant comparisons with freshly isolated mouse islets could be performed. As evidenced by light microscopy, there was an excellent morphologic preservation of islets cultured in either the high or the low glucose medium. Similarly, the rates of oxygen consumption, glucose oxidation and insulin release responded responded to glucose throughout the culture period in a manner qualitatively similar to these responses in freshly isolated islets. The most obvious quantitative metabolic alterations observed in the cultured islets were increased rates of respiration and glucose oxidation and a decreased basal rate of insulin release. Islets cultured in the high glucose medium responded to glucose with a higher glucose oxidation and a lower rate of insulin release than those cultured in the low glucose medium for a similar period of time. The insulin content of the islets decreased markedly during the initial six days of the culture period. The results indicate that with the present technic for organ culture of isolated mouse islets, the β cells retain several of their characteristic metabolic responses during prolonged in vitro culture. The method should be useful for providing new information on the long-term effects in vitro of various factors on the structure and metabolism of the pancreatic β cell.