ALTERED REGULATION OF INSULIN-SECRETION IN ISOLATED ISLETS OF DIFFERENT SIZES IN AGING RATS

Glucose-stimulated secretion of immunoreactive insulin (IRI) was examined in perifused pancreatic islets of Langerhans of different sizes isolated from fed and fasted, Sprague-Dawley rats aged 2- to 24-months. Small and large islets show distinctly different biphasic secretory responses which are modified during starvation or aging. The rate of IRI secretion is several fold greater in large than in small islets, irrespective of donor age or nutritional status. Starvation severely reduces the rate of IRI secretion, essentially abolishing the stimulatory effect of glucose in small islets from fasted, old rats. Aging inhibits IRI secretion, but to a far greater degree in small than in large islets. The increased number of large islets in the pancreas of aging rats may represent a physiological compensatory response to the diminished functional capability of small islets with respect to glucose-stimulated secretion of IRI. © 1979 Academic Press, Inc. All rights of reproduction in any form reserved.