Sodium-Calcium Exchanger in Pig Coronary Artery.

Sodium-Calcium Exchanger in Pig Coronary Artery. Adv Pharmacol. 2017;78:145-170 Authors: Grover AK Abstract This review focuses on the sodium-calcium exchangers (NCX) in the left anterior descending coronary artery smooth muscle. Bathing tissues in Na(+)-substituted solutions caused them to contract. In cultured smooth muscle cells, it increased the cytosolic Ca(2+) concentration and extracellular entry of (45)Ca(2+). All three activities were attributed to NCX since they were inhibited by NCX inhibitors. The tissues also expressed the sarco/endoplasmic reticulum (SER) Ca(2+) pump SERCA2b whose activity was much greater than that of NCX. Inhibiting SERCA2b with thapsigargin decreased the NCX-mediated (45)Ca(2+) accumulation by the cells. The decrease was not observed in cells loaded with the Ca(2+)-chelator BAPTA. The results are consistent with a limited diffusional space model with a proximity between NCX and SERCA2b. NCX molecules appear to be colocalized with the subsarcolemmal SERCA2b based on studies on membrane flotation experiments and microscopic fluorescence imaging of antibody-labeled cells. Thapsigargin inhibition of SERCA2b moved NCX even closer to SER. This provides a model for the NCX-mediated Ca(2+) refilling of SER in the arterial smooth muscle. The model for the NCX-mediated refilling of the depleted SER proposed for smooth muscle did not apply to endothelium in which NCX levels were greater and SERCA levels were lo...
Source: Advances in Pharmacology - Category: Drugs & Pharmacology Authors: Tags: Adv Pharmacol Source Type: research