Changes in bioelectrical parameters of isolated frog skin epithelium caused by monocrotophos.

The effect of monocrotophos on the bioelectric parameters of frog skin: potential difference (PD), short-circuit current (SCC), the rate of active sodium ion transport, resistance (R), summed ionic permeability, was studied and it was demonstrated that the tested pesticide added to the medium on the external surface of the skin at the concentrations 4.5 X 10(-3)M and 1.1 X 10(-2)M had no significant effects on these parameters. This might have been connected with the presence on the skin surface mechanisms protecting it against the action of this pesticide. After addition to the medium on the internal side of the skin in a higher concentration it produced an irreversible increase in SCC value and decreased tissue resistance. It seems that the most likely cause of the observed changes were disturbances in the molecular structure of the plasma membrane with its stabilization of the sodium channels in the open position.