Localization and quantitation of cardiac annexins II, V, and VI in hypertensive guinea pigs

Annexins are characterized by Ca2+-dependent binding to phospholipids. Anne xin II mainly participates in cell-cell adhesion and signal transduction, w hereas annexins V and VI also seem to regulate intracellular calcium cyclin g. Their abundance and localization were determined in left ventricle (LV) and right ventricle (RV) from hypertensive guinea pigs, during the transiti on from compensatory hypertrophy to heart failure. Immunoblot analysis of a nnexins II, V, and VI revealed an increased accumulation (2.6-, 1.45-, and 2.3-fold, respectively) in LV from hypertensive guinea pigs and no modifica tion in RV. Immunofluorescent labeling of annexins II, V, and VI; of Na+-K-ATPase; and of sarcomeric alpha-actinin showed that in control LV and RV, 1) annexin IT is present in nonmuscle cells; 2) annexins V and VI are mainl y observed in the sarcolemma and intercalated disks of myocytes; 3) annexin s II, V, and VT strongly label endothelial cells and adventitia of coronary arteries; and 4) annexin VI is present in the media. At the onset of heart failure, the most striking changes are the increased protein accumulation in LV and the very strong labeling of annexins II, V, and VI in interstitia l tissue, suggesting a role in fibrosis development and cardiac remodeling.