Enhanced endothelin(A) receptor-mediated calcium mobilization and contraction in organ cultured porcine coronary arteries

Arterial injury models for coronary artery disease have demonstrated an enh anced expression and function of either the endothelin(A) or endothelin(B) (ETA or ETB) receptor subtype. We hypothesized that organ culture would enh ance the physiological function of ET receptors in the porcine right corona ry artery. Arteries were either cold stored (4 degreesC) or organ cultured (37 degreesC) for 4 days. After 4 days, the artery was either 1) sectioned into rings to measure the ET-1-induced isometric tension response (3 x 10(- 10)-3 x 10(-7) M), or 2) enzymatically dispersed and the isolated smooth mu scle cells imaged using fura-2 to measure the myoplasmic calcium (Ca-m) res ponse to 3 x 10(-8) M ET-1 (similar to EC50). Isometric tension and Ca-m to ET-1 were measured in the absence and presence of bosentan (nonselective E TA or ETB receptor antagonist), BQ788 (ETB-selective antagonist), and BQ123 (ETA-selective antagonist). Compared with cold storage, organ culture indu ced a 2-fold increase in tension development (3 x 10(-7) M ET-1) and Ca-m ( 3 x 10(-8) M ET-1), which was inhibited with bosentan, thus confirming the enhanced responses to ET-1 were due to ET receptor activation. BQ123 also i nhibited the enhanced contraction and Ca-m responses to ET-1. In contrast, BQ788 failed to inhibit tension development and Ca-m responses to ET-1 in o rgan culture and cold storage. Sarafotoxin 6C (ETB agonist) failed to elici t an increased Ca-m response in organ culture compared with cold storage. O ur results indicate the increased tension development and Ca-m responses to ET-1 in organ culture are attributable to ETA receptors, and not ETB recep tors.