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Ultrastructural cytochemistry of atrial and ventricular cardiocytes of the bullfrog (Rana catesbeiana). Relationship of specific granules with reninlike activity of the myocardium.

Authors
Type
Published Article
Journal
Canadian Journal of Physiology and Pharmacology
0008-4212
Publisher
Canadian Science Publishing
Publication Date
Volume
58
Issue
12
Pages
1463–1476
Identifiers
PMID: 7016273
Source
Medline

Abstract

The ultrastructural cytochemical reactivity, renin activity, and cathepsin D activity of atria and ventricle of the bullfrog have been assessed. The specific granules (A, B, and D) were found to be argentaphobic when ultrathin sections of Araldite-embedded atria and ventricle were stained according to the periodic acid-thiocarbohydrazide-silver proteinate technique of Thiery. The entire core of the specific granules was moderated positive after ultrathin sections of glutaraldehyde-fixed, glycol methacrylate embedded atria and ventricle were stained by phosphotungstic acid at a low pH. A similar reaction was shown by the cell coat, intercalated discs, residual bodies (C granules), and Z discs as well as by a very small portion of the Golgi complex. Incubation of ultrathin sections of atria and ventricule fixed only in glutaraldehyde and embedded in glycol methacrylate with either pronase or trypsin resulted in selective digestion of specific granules and Z discs and, to a much lesser degree, of the cell coat. As cathepsin D activity and renin activity were present in both atria and ventricle, the generation of angiotensin I by these cardiocytes might have been due to either enzyme. Nevertheless, because of the glycoprotein nature of specific granules and of the endocrinelike ultrastructure of atrial and ventricular cardiocytes in the frog, the present results raise the possibility that specific granules may contain renin.

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