Enhanced EndothelinA Receptor-Mediated Calcium Mobilization and Contraction in Organ Cultured Porcine Coronary Arteries1
- 1Vascular Biology Laboratory, Dalton Cardiovascular Research Center, and Department of Physiology, School of Medicine, University of Missouri, Columbia, Missouri (B.J.F.H., B.R.W., M.S.); and 2Department of Physiology, School of Medicine, East Carolina University, Greenville, North Carolina (L.C.K.)
Abstract
Arterial injury models for coronary artery disease have demonstrated an enhanced expression and function of either the endothelinAor endothelinB (ETA or ETB) 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 (Cam) response to 3 × 10−8 M ET-1 (∼EC50). Isometric tension and Cam to ET-1 were measured in the absence and presence of bosentan (nonselective ETA or ETB receptor antagonist), BQ788 (ETB-selective antagonist), and BQ123 (ETA-selective antagonist). Compared with cold storage, organ culture induced a 2-fold increase in tension development (3 × 10−7 M ET-1) and Cam(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 Cam responses to ET-1. In contrast, BQ788 failed to inhibit tension development and Cam responses to ET-1 in organ culture and cold storage. Sarafotoxin 6C (ETB agonist) failed to elicit an increased Cam response in organ culture compared with cold storage. Our results indicate the increased tension development and Cam responses to ET-1 in organ culture are attributable to ETA receptors, and not ETBreceptors.
Footnotes
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Send reprint requests to: Michael Sturek, Ph.D., Department of Physiology, MA415 Medical Sciences Building, School of Medicine, University of Missouri, Columbia, MO 65212. E-mail:sturekm{at}missouri.edu
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↵1 This study was supported by National Institutes of Health Grants RR13223 and HL62522 (to M.S.) and an American Heart Association Predoctoral Fellowship (to B.J.F.H.).
- Abbreviations:
- ET-1
- endothelin-1
- ETA
- endothelinA
- ETB
- endothelinB
- LAD
- left anterior descending coronary artery
- Cam
- myoplasmic calcium
- DAPI
- 4′,6-diamidino-2-phenylindole dihydrochloride
- PSS
- physiological salt solution
- 80K
- 80 × 10−3 M KCl solution
- Tmax
- response to a maximal concentration of an agonist
- SR
- sarcoplasmic reticulum
- OC
- organ culture
- CS
- cold storage
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- Received May 22, 2000.
- Accepted July 31, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
