Inward Rectifier and Delayed Outward Potassium Currents in Isolated Guinea-Pig Ventricular Myocytes: Maturation and Its Role in Repolarization

分離天竺鼠心室細胞之內向整流及遲發性外向鉀電流之成熟以及其再極化角色

吳美環(Mei-Hwan Wu) ； 蘇銘嘉(Ming-Jai Su) ； 呂鴻基(Hung-Chi Lue)

《Acta Paediatrica Sinica》 33卷5期 (1992/10) Pp. 363-371

摘要

In accord with previous reports, we have found that action potentials triggered from isolated mature (＞1 month) guinea-pig ventricular myocytes showed a longer duration than those from the neonate (＜1 day). A whole-cell voltage-clamp technique has been used to identify the postnatal changes of inward rectifier (I(subscript K1)) and delayed outward potassium currents (I(subscript k)) which may be related to the action potential transition. Our results have shown that the degree of maturation of the neonatal guinea-pig is much advanced, as compared to neonatal rabbits and rats. Slope conductance (1230±110 pS/pF, n=10, for neonatal, and 1450±450 pS/pF, n=l0, for mature guinea-pig, p＞0.05) and the inward rectification occurring over a potential range from -50 to -10mV were relatively similar between the neonatal and mature guinea-pig myocytes. But, the slope conductance of I(subscript k) was significantly greater in neonatal (702±80 pS/pF, n=10) guinea-pig myocytes than in the mature (194±23 pS/pF, n=10, p＜0.0l). Therefore, we suggest that (1) the maturation of I(subscript k) appears later than that of I(subscript k) (2) age-related decrease of the slope conductance of I(subscript k) could contribute to an age- related lengthening of the action potential duration.

並列摘要

In accord with previous reports, we have found that action potentials triggered from isolated mature (＞1 month) guinea-pig ventricular myocytes showed a longer duration than those from the neonate (＜1 day). A whole-cell voltage-clamp technique has been used to identify the postnatal changes of inward rectifier (I(subscript K1)) and delayed outward potassium currents (I(subscript k)) which may be related to the action potential transition. Our results have shown that the degree of maturation of the neonatal guinea-pig is much advanced, as compared to neonatal rabbits and rats. Slope conductance (1230±110 pS/pF, n=10, for neonatal, and 1450±450 pS/pF, n=l0, for mature guinea-pig, p＞0.05) and the inward rectification occurring over a potential range from -50 to -10mV were relatively similar between the neonatal and mature guinea-pig myocytes. But, the slope conductance of I(subscript k) was significantly greater in neonatal (702±80 pS/pF, n=10) guinea-pig myocytes than in the mature (194±23 pS/pF, n=10, p＜0.0l). Therefore, we suggest that (1) the maturation of I(subscript k) appears later than that of I(subscript k) (2) age-related decrease of the slope conductance of I(subscript k) could contribute to an age- related lengthening of the action potential duration.

並列關鍵字

postnatal maturation ； potassium channel