Nuclear localization of aldolase A in pig cardiomyocytes

The subcellular localization of the muscle aldolase (aldolase A) in cardiomyocytes was determined immunocytochemically by light and electron microscopy. The enzyme was localized in the cytoplasm and also in cardiomyocyte nuclei. Inside the nuclei it was preferentially localized in the heterochromatin region. The nuclear localization was confirmed by the measurement of aldolase activity in subcellular fractions of a heart muscle, and in isolated nuclei of cardiomyocytes. There was no detectable aldolase activity in isolated cardiomyocyte nuclei fractions if the fraction was not preincubated with a solution containing Triton X-100 and KCl. The calculated concentration of aldolase in the nucleus was about 0.6 micro M. This paper is the first report on the localization of aldolase A inside cardiomyocyte nuclei.