Energy dispersive X-ray microanalysis of zinc and calcium in organelles of insulin-producing cells of the mouse, rat, and a fish.

: By means of energy dispersive X-ray microanalysis in the scanning-transmission electron microscope, spectra were obtained from quick-frozen, cryo-ultramicrotome cut, freeze-dried sections of insulin cells from a fish and a mouse. It was shown that both zinc and calcium are present in significant quantities in native islet-cell beta-granules. In the beta-granules of the rat RINm5F insuloma cells calcium, but not zinc, seemed to accumulate; the zinc contents in the secretion granules of these neoplastic beta-cells were probably below the detection limit.