쥐 심근 세포의 [3H] Ouabain 결합과 45Ca2+섭취에 미치는 Ouabain의 영향

[3H] Ouabain Binding and Effect of Ouabain on 45Ca2+-Uptake in Rat Cardiac Myocytes

Specific [3H] ouabain binding and Ca2+-uptake were measured to elucidate the role of high affinity [3H] ouabain binding site in rat cardiac myocytes which contain 65% of rod cells. High affinity [3H] ouabain binding site, which is about 3% of total pump sites, with apparent dissociation constant (KD) of 1.1 X 10-7M and maximum binding site concentration (Bmax) of 1.2pmol/mg protein (1.754 X 105cells) were identified. At the concentration of 10-7M to 10-4M, ouabain produced concentration-dependent increase in Ca2+-uptake of myocytes. The effect of ouabain on Ca2+-uptake was not effected by membrane depolarization (elevated K+ in incubation medium) or verapamil. These results suggest that in rat ventricular myocytes the ouabain receptor complex to high affinity site may increase Na+-Ca2+ exchange across the sarcolemmal membrane by inhibition of Na+,K+-ATPase.