The effect of [Ca]o on the resting potential in newborn and adult rat ventricular muscles |
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Authors: | T Yamamoto |
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Abstract: | Microelectrode studies were carried out to examine the effect of varied [Ca]o on resting potentials of newborn and adult rat ventricular muscles. The ratio of membrane permeabilities to sodium and potassium (PNa/PK) estimated from the constant-field equation was about 0.03 in 2 mM [Ca]o in both newborn and adult preparations. Membrane hyperpolarization was observed in adult preparations when [Ca]o was increased from 1 mM to 10 mM, whereas the resting potential of newborn preparations was little hyperpolarized. In 10 mM [Ca]o, PNa/PK was 0.01 in adult and was still 0.03 in newborn. The hyperpolarization observed in adult tissue was reduced in low [Na]o, which is inconsistent with the constant-field equation. A possible mechanism of this hyperpolarization is discussed. |
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