title: 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.
abstract: 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.
mesh_terms: 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*
chemical_list: D002132:Calcium Radioisotopes; D004533:Egtazic Acid; D007811:Lanthanum; D014700:Verapamil; D009543:Nifedipine; D011188:Potassium; D002118:Calcium