Aconitine alters connexin43 phosphorylation status and [Ca2+] oscillation patterns in cultured ventricular myocytes of neonatal rats

Aconitine, a highly poisonous type of alkaloid, has a widespread effect in stimulating the membranes of cardiomyocyte. However, other effects of aconitine on cardiomyocyte are unknown. In this study, we investigated whether aconitine also affects the phosphorylation status of connexin43 (Cx43) and intracellular [Ca2+] oscillation patterns in cultured ventricular myocytes of neonatal rats. As determined by Western blot analysis, a decreased percentage (47.68 ± 2.29%) of phosphorylated Cx43 (P-Cx43) and a concomitant increased percentage (52.32 ± 2.29%) of nonphosphorylated Cx43 (NP-Cx43) were found in aconitine-treated cultures, compared to the controls (82.77 ± 2.04% for P-Cx43 and 17.23 ± 2.04% for NP-Cx43). Quantitative immunofluorescent microscopy revealed similar changes in phosphorylation status occurring in Cx43 containing gap junctions in the cultures under the same treatment conditions. Real-time laser scanning microscopy indicated that intracellular [Ca2+] oscillations were relatively stable in control cultures, with occasional calcium sparks; after being treated with aconitine, high frequency [Ca2+] oscillations emerged, whereas typical calcium sparks disappeared. Furthermore, Western blot analysis revealed that, after aconitine treatment, the amount of phosphorylated PKCα decreased significantly. These observations suggest that aconitine not only induces dephosphorylation of Cx43 and PKCα, but also alters intracellular [Ca2+] oscillation patterns in cultured cardiomyocytes.