ACTION POTENTIAL MODIFICATIONS IN RAT MYOCARDIAL CELLS INDUCED BY HYPERVITAMINOSIS A

¹ Institute of Human Physiology of the University of Pavia, Pavia (Italy)

Ventricular cell action potentials were measured in situ using intracellular microelectrodes in the hearts of hypervitaminotic A rats, both at the spontaneous rate and at rates externally increased to various higher levels. The action potentials were much modified (decrease in amplitude, in depolarization rate, in fast and slow repolarization rate, and increase in partial and total duration). Excess of vitamin A also appeared to bring about a rise in spontaneous heart rate. Ion fluxes in myocardial cells at high levels of vitamin A seemed to be somewhat uncoupled from cardiac metabolism. The results obtained indicate that the changes in cardiac electrogenesis may be specifically related to the effects of an excess of vitamin A on cell membrane structure and consequently on permeability and ion fluxes through the membranes.

Note:

This work was supported in part by a grant from Consiglio Nazionale delle Ricerche, Rome.

We are grateful to Professor G. Rapuzzi for his invaluable advice and criticism of the manuscript, and to Mr D. Bonizzoni for his skilful technical assistance.

We wish to thank Prodotti Roche of Milan for the generous supply of ‘Arovit’.