Abstract
The location and proportions of beta-1 and beta-2 adrenoceptors in canine coronary arteries (0.5-2 mm) has been examined by autoradiography. X-ray film and nuclear emulsion-coated coverslips were exposed to sections of coronary artery previously incubated with [125I]iodocyanopindolol (50 pM) in the absence and presence of ICI 118,551 (70 nM) to block beta-2 adrenoceptors, CGP 20712A (100 nM) to block beta-1 adrenoceptors or (-)-propranolol (1 microM) to define nonspecific binding. The medial smooth muscle of the coronary artery had an even distribution of beta-1 adrenoceptors and two populations of beta-2 adrenoceptors, one evenly distributed and the other highly localized. Beta-2 adrenoceptors were also located on nerve tissue and in the adventitia. There was no evidence for localization of beta adrenoceptors on endothelial cells. Quantitative autoradiography was performed using computer-assisted image processing and the program AVID. The binding of [125I]cyanopindolol was saturable (KD = 50 pM) and competition binding curves with the beta-1 selective antagonist CGP 20712A and beta-2 selective antagonist ICI 118,551 showed beta-1 and beta-2 adrenoceptors in the proportions of 85:15% in both 0.5- and 2-mm arteries.
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|