Demonstration of calcium in pancreatic islets - Light-microscope observations in activated and inactivated B cells of mice

The GBHA [=glyoxal bis (2-hydroxyanil)] technique allows light microscopic demonstration of mobile calcium in some soft tissues. We used this method to compare granulation and calcium content of B cells of mice in the normal state and under conditions of suppression and of acute and chronic stimulation. For the suppression of B cells, hypoglycaemia was induced by the injection of bovine insulin. Acute stimulation of B cells by hyperglycaemia was achieved by a single injection of anti-insulin serum of guinea-pigs, and chronic stimulation by repeated injections of this antiserum for 4 days. In untreated animals the GBHA reaction indicated high amounts of calcium located selectively within the cytoplasm of B cells. In contrast to the degree of granulation, the calcium content showed slight variations from islet to islet, which may indicate differences in the secretory activity of the different islets at the time of sacrifice. Cellular calcium seemed to be loosely bound; it was possible to remove it with the aid of aqueous fixation fluids, while the addition of oxalate caused it to be retained. The suppressed B cells showed marked granulation and a uniformly high calcium content. After acute stimulation, there was a slight decrease of granulation in some B cells; the amount of calcium varied from cell to cell and was markedly elevated in some. The differences in the animal groups were only discrete and demand further evaluation. In contrast, after chronic stimulation the B cells showed signs of hypersecretory degeneration, marked degranulation and an almost total loss of stainable calcium. In addition we observed slight insulitis, which is thought not to be a consequence of chronic stimulation, however, but a response to the deposition of immune complexes within the islet. Our findings suggest that the high amounts of calcium detectable in the B cells by light microscopy depend predominantly on the degree of granulation. In addition, in cases of identical granulation an increased secretory activity seems to induce a slight elevation of cellular calcium.