The Estimation of Effects of Heavy Metals on Membrane and Action Potential
DOI:
https://doi.org/10.5644/Radovi.298Abstract
Using the technique of intracellular membrane potential registration membrane potential was measured, of the smooth muscle cells in standard Tyrode solution in the presence of Mn2+, Cd++ and Pb++ as well as in acalcic Tyrode solution without Ca++ but in the presence of Mn+ + and Cd"*. Mn+ + in final concentration of 10-5 — 10-3 M in standard Tyrode solution rt the beginning caused a mild decrease of rest potential and the decrease to reach 72°/o of the start value at the end of the first minute. However, from the second minute after application of Mn++ the rest potential was Progressive by regenerated and at the end of the eight minute it reached its start value. Ca++ added in concentration of 1,5 mM caused hyperpolarisation of 10% over the start value. If Mn++ were added in acalcic solution, during the first minute of acalcic State rest potential decreased to 65% of the start value. From the second minute of the application of Mn++ membrane potential was regenerating and during the fourth minute it reached the start value. In the course of this experiment gradual hyperpolarisation was observed which reached 36% over the start value. Ca++ added in Tyrode solution in concentration of 1.5 mM caused further hyperpolarisation to 57% over the start value. Pb++ added in the final concentration 10-5 — 10-1 M in the standard Tyrode solution caused irreversible decrease of the membrane potential to 64% of the start value, this partial depolarisation was maintained during the experiment without tendency to a regeneration of the rest potential. Cd++ in the standard Tyrode solution in concentration 10-5 — 10-3 M caused a mild initial hyperpolarisation. In acalcic solution the rest potential in the presence of Cd++ showed the Progressive decrease to 56% of the start value. No tendency of the regeneration of membrane potential was observed. Using the methods of electrostimulation and oscillography analysis of four essential parameters of the compound action potential, the effects of Hg++ on the excitable cell membranes of isolated frog sciatic nerves were studied. The results showed that Hg++ in concentration of 5 mM caused a strong depression of amplitude of action potential, an increase in threshold excitation and prolongation of latency. The changes of amplitude of the action potential and latency were reversible, but the effects of Hg++ on threshold excitation were prolonged.
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