Abstract

Arterial injury models for coronary artery disease have demonstrated an enhanced expression and function of either the endothelin_Aor endothelin_B (ET_A or ET_B) receptor subtype. We hypothesized that organ culture would enhance the physiological function of ET receptors in the porcine right coronary artery. Arteries were either cold stored (4°C) or organ cultured (37°C) for 4 days. After 4 days, the artery was either 1) sectioned into rings to measure the ET-1-induced isometric tension response (3 × 10⁻¹⁰–3 × 10⁻⁷ M), or 2) enzymatically dispersed and the isolated smooth muscle cells imaged using fura-2 to measure the myoplasmic calcium (Ca_m) response to 3 × 10⁻⁸ M ET-1 (∼EC₅₀). Isometric tension and Ca_m to ET-1 were measured in the absence and presence of bosentan (nonselective ET_A or ET_B receptor antagonist), BQ788 (ET_B-selective antagonist), and BQ123 (ET_A-selective antagonist). Compared with cold storage, organ culture induced a 2-fold increase in tension development (3 × 10⁻⁷ M ET-1) and Ca_m(3 × 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 inhibited 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 organ culture and cold storage. Sarafotoxin 6C (ET_B agonist) failed to elicit an increased Ca_m response in organ culture compared with cold storage. Our results indicate the increased tension development and Ca_m responses to ET-1 in organ culture are attributable to ET_A receptors, and not ET_Breceptors.