SOME ASPECTS OF SILVER IMPREGNATION OF THE ISLETS OF LANGERHANS IN THE RAT

Abstract

By using a modification of Davenport''s alcoholic silver nitrate method for impregnating nerves, it was possible to obtain a distinct argyrophil reaction on thin paraffin sections from rat pancreas which had been fixed either in formalin or Bouin''s solution. Since this was followed by a removal of silver with subsequent granule staining according to Gomori, it become clear that the distinctly blackened cells comprised only some of the A cells. Some post-mortem change seemed to be an essential prerequisite of the argyrophil reaction, since this almost completely failed to appear after fixation in an ice-cold Bouin''s solution. The reducing material was considerably resistant to acids; strongly blackened islet cells could be observed even after refixation in hydrochloric acid at a pH of 0.5. Although a preoxidation, e. g. with an acid solution of potassium permanganate, is essential for the differentiation of the islet cells with the modern granule stains, such treatment results in the argyrophil reaction becoming weaker or not appearing at all. Actual blackening, except in the case of those A cells, which could be distinguished as silver cells even after a short time, could not be produced by lengthening the impregnation time, but instead, the argyrophil reaction tended to decrease after a certain optimal period. The observation that among those cells, which by granule staining were classified as A cells, a separate fraction with distinctly blackened cytoplasm could be distinguished, led to the suggestion that the blackened cells should be called A1 cells and the remaining ones, A2 cells.