Ultrastructure of the carotid body of the cat as revealed by various fixatives and the use of reserpine.

Abstract

AbstractCarotid bodies from 11 cats were prepared for study with the electron microscope. All cats used were initially healthy and weighed from 1.5 to 4.0 Kg. Four cats were given daily doses of reserpine 1.5 mg/Kg for 2, 3, 4 or 12 days; the other cats were untreated. Carotid bodies were fixed by immersion in Dalton's fluid, collidine buffered osmic acid or 3% potassium permanganate in 0.1 M phosphate buffer. Other carotid bodies were fixed by perfusion with buffered formalin or with 3% glutaraldehyde in phosphate buffer. Each fixative produced distinct differences in the appearance of the carotid body, particularly in the size and opacity of the granules within the characteristic vesicles of glomus cells (type I). After Dalton's fixative the granules were faint and inconspicuous whereas after osmic acid fixation the granules were very dense but small in comparison to the size of the enclosing vesicular membrane. Aldehyde fixation resulted in very dense granules that almost completely filled the vesicles but permanganate fixation produced vesicles that were devoid of the dense central cores except for a very few. Carotid bodies from reserpine treated cats that were fixed in osmic acid displayed empty vesicles while those from reserpinized animals fixed by perfusion with glutaraldehyde revealed granules that differed little from normal in numbers, size and density. However, vesicles in the adrenal medulla and in sympathetic nerve endings in the pineal gland from the same animals contained empty vesicles. The results are regarded as evidence of a different degree or method of binding between catecholamines and other components of the vesicles in glomus cells when compared to similar vesicles in sympathetic nerve endings and the adrenal medulla.