Morphological and Histochemical Methods for the Study of Paraganglionic Cells

Abstract

Chromaffin cell granules reduce osmium tetroxide, appearing osmiophilic or electron dense when studied with the light or electron microscope. The reaction is in no way specific, but fixation with buffered solutions of osmium tetroxide provides good preservation of tissue and distinct demonstration of the catecholamine-storing organelles. Osmium tetroxide-potassium dichromate mixtures are less advantageous because of the limited tissue penetration of this fixative. The classic formol-dichromate mixture permits visualization of electron-dense granules but leaves cytological details nearly indiscernible (Brücke et al. 1971). Permanganate is reduced to MnO₂ by catecholamines. It has been recommended as an appropriate fixative for demonstration of dense-core vesicles in adrenergic terminals (Hökfelt 1969,1973; Hökfelt and Jonsson 1968): immersion of small tissue blocks in ice-cold 3%–6% solutions of KMnO₄ for 2–4 h is followed by washing of the specimens in Ringer solution and en bloc staining with uranium ions. In paraganglionic cells (carotid body), Duncan and Yates (1967) generally found the specific granules to be devoid of a dense core when fixation was performed in 3% KMnO₄. Similar results were reported by Grönblad and Eränkö (1978), and Hervonen et al. (1978 e). Kanerva et al. (1977) found paraganglionic cells in sympathetic ganglia (SIF cells) to contain electron-dense granules after permanganate fixation, whilst adrenomedullary chromaffin cells contained empty vesicles. The authors state that these findings need further clarification because “permanganate is widely used in monoamine fine structural cytochemistry”.