Tissue culture of fetal rat islets: corticosterone promotes D cell maintenance and function.

Fetal pancreatic islets were cultured using a recently described technique (1). After 1 day in culture, half of the plates were continued in control medium and half were grown in identical medium supplemented with corticosterone (0.1 microgram/ml). Media were renewed daily, and culture was continued for a total of 8 days. Insulin, glucagon, and somatostatin contents in the media were determined daily. These hormones were also estimated in the tissue at the time of plating, and after 1 and 8 days in culture. Islets were fixed on day 8, and the cells containing each of these hormones were identified by immunocytochemical staining. Corticosterone supplementation of the medium resulted in a 3-fold increase in the somatostatin concentration of the medium. The insulin and glucagon contents of the supplemented medium were slightly reduced. On day 8, there was no difference in the insulin content of the cultured tissue regardless of medium. The glucagon and somatostatin contents of the tissue grown in the steroid-supplemented medium were greater (1.8- and 3.1-fold, respectively) than those of the tissue grown in control medium. D cells were rare in the islets grown in control medium volume density, 0.4%, but were more numerous in the islets maintained in supplemented medium (2.2%). Islets grown in corticosterone-supplemented medium lacked an insulin secretory response to 22 mM glucose. These findings indicate that the volume densities of the cells within the islets can be altered during an 8-day period in culture, suggesting that nutritional and other requirements of the individual subpopulations of islet cells may be different. In addition, corticosterone may prevent the maturation of the secretory responsiveness of cultured B cells to glucose.