Measurement of slowly exchanging 45Ca in rat aorta without using EGTA or lanthanum and its application to quantify the effects of the calcium entry blockers nifedipine and verapamil.
In rat aortic strips a method was developed to measure a fraction of slowly exchanging 45Ca, which correlates with contraction and the cytosolic Ca pool that is enhanced by K+-induced depolarization. In this method no EGTA or lanthanum are used, but the strips are washed for 45 min with a Tyrode solution at 4 degrees C. The K+ depolarization induced increase in 45Ca and contraction was concentration-dependently inhibited by verapamil and nifedipine. Since lanthanum and EGTA affect cellular membranes, this method may allow a more physiological approach to the measurements of slowly exchanging 45Ca.
D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D007811:Lanthanum / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014700:Verapamil / Q000494:pharmacology*
D002132:Calcium Radioisotopes; D004533:Egtazic Acid; D007811:Lanthanum; D014700:Verapamil; D009543:Nifedipine; D011188:Potassium; D002118:Calcium