Estimates of Na+-K+ pumping in intact canine iliac arteries.
Estimates of Na+ pumping capacity were made using Na+-loaded canine iliac arteries. Ouabain-sensitive uptake of 204Tl or 86Rb was used to measure near-maximal pump rates and [3H]ouabain binding to measure the number of pump sites. Compared with Rb+, Tl+ had the higher affinity for the pump and showed better signal-to-noise characteristics. Maximal uptakes were 0.545 mumol . g-1 . min-1 for Rb+ and 0.40 mumol . g-1 . min-1 for Tl+. Specific ouabain binding (Kd: 28.62 +/- 0.58 nM) was inhibited by external K+, Tl+, and Rb+ and a maximal binding of 51.6 pmol/g wet weight translated into 3.2 X 10(13) sites per gram wet weight. Using these values, the maximal values of K+ transported per pump site per minute lie between 7752 and 10562. If each activation of the pump moves 2K+, the turnover rates could lie between 3876 and 5281 per minute.
D000818:Animals; D001692:Biological Transport; D001834:Body Water / Q000378:metabolism; D004285:Dogs; D007083:Iliac Artery / Q000378:metabolism*; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D010042:Ouabain / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D011868:Radioisotopes; D012413:Rubidium; D012964:Sodium / Q000378:metabolism*; D013793:Thallium
D011868:Radioisotopes; D010042:Ouabain; D012964:Sodium; D013793:Thallium; D012413:Rubidium; D011188:Potassium