Troponin bound calcium in electron micrographs of myocardial cells as demonstrated by the potassium-antimonate technique

Abstract

Following the K-antimonate reaction in atrial myocardial tissue, a pattern of evenly spaced cross striations of antimonate precipitates is demonstrated along the myofilaments. This spacing, found in both turtle and mouse atria, has a periodicity of about 400 Å. In order to test the shifts of the antimonate reaction product in the tissue, a comparison is made between the localization of the antimonate precipitate as seen in viz. thin plastic sections and in cryo-ultra sections being dry-cut at -90° C from N₂ frozen tissue. Preliminary results suggest only minor distributional differences in the sarcomeric pattern. On the basis of these tests, and, on the basis of previous studies by means of X-ray microanalysis, it is suggested that the periodic pattern of evenly spaced precipitates, reflects the localization of troponin bound calcium along the thin filaments during contraction.