A FLUORESCENT REACTION FOR MONOAMINES IN THE INSULIN PRODUCING CELLS OF THE GUINEA-PIG

Abstract

Certain catecholamines and tryptamines condense in freeze-dried tissues with formaldehyde to form intensely fluorescent products. A distinct fluorescence has recently been demonstrated in the islets of Langerhans from several species with this sensitive and specific technique. The fluorescent reaction of the islets has been studied in more detail in the guinea-pig. Using a combination of fluorescence microscopy with subsequent silver impregnation and granule staining on the same section it was found that the fluorescent cells were identical with the B cells. The B cells exhibited no, or only weak, fluorescence after administration of reserpine. The colour of the emitted fluorescent light suggests that the B cells contain a tryp-tamine rather than a catecholamine. Since the fluorescent material was distributed in fine cytoplasmic granules the amine may be assoc-iated with the aldehyde-fuchsin positive granules which are regarded as the storage site for insulin or some insulin precursor. No support was found for the previous concept of an adrenergic parenchymatous innervation of the islets of Langerhans.