PRODUCTION AND ELIMINATION OF MYELOID BODIES BY CULTURED PANCREATIC-ISLET CELLS

B-Cells of cultured rat pancreatic islets contain myeloid bodies. Ultrastructure and acid phosphatase cytochemistry suggests that they originate from Golgi endoplasmic reticulum lysosomes. Many such bodies seen extracellularly appear to be released by exocytosis. Large numbers of myeloid bodies are seen in cultures exposed to 10-5M cyproheptadine (CPH) for 8 days. Accumulation probably results from reduced elimination rather than increased production since both the number of extracellular myeloid bodies and the acid phosphatase activity of the medium are significantly decreased compared with controls. Concomitantly, intracellular Ca2+ is decreased and insulin secretion inhibited. The observation that CPH inhibits the exocytotic release of a variety of hormones by reducing Ca2+ influx suggests that the elimination of myeloid bodies normally occurs by Ca2+-dependent exocytosis. These CPH effects are fully reversible when the islets are cultured for a further 8 days in CPH-free medium. © 1979 Academic Press, Inc.