Changes in cardiomyocyte proliferation process of the lake frog Pelophylax ridibundus (Pallas, 1771) under the effect of cadmium ions

The study investigated changes in the cardiomyocyte proliferation process of the lake frog Pelophylax ridibundus (Pallas, 1771) during tadpole metamorphosis under the effect of various concentrations of cadmium ions. Lake frog larva were raised in pond water containing 0.002 mg/L, 0.02 mg/L, and 0.1 mg/L of cadmium ions. The alkaline tissue dissociation method was used to obtain isolated cardiomyocytes. The mitotic index (percentage of dividing cells) and the index of binucleated cardiomyocytes (percentage of binucleated cells) were counted in smears of isolated cells. The research showed that the development of lake frog tadpoles in water containing various concentrations of cadmium ions did not cause significant changes in the morphology of cardiac myocytes. Most cardiomyocytes had a cylindrical shape, an oval centrally located nucleus, and a small number of lateral and terminal processes. Both uninucleated and binucleated cardiomyocytes were present. Under the effect of cadmium ions at various concentrations in the tadpoles’ environment during the metamorphosis period, there was an inhibition of proliferative activity of cardiac muscle cells in the atria and ventricle at all studied developmental stages. This effect was most noticeable at a cadmium concentration of 0.02 mg/L. A systematic decrease in the index of binucleated cardiomyocytes in the atrium and ventricle of the lake frog was observed. The altered course of cardiomyocyte proliferation of cardiac myocytes may be due to disruption of the synthesis or structural organization of cytoskeleton proteins involved in spindle formation and chromosome separation during anaphase of mitosis

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