Contractile responses of coronary collateral (COL) arteries to vasopressin (VP) are markedly enhanced while in contrast, responses of COL arteries to endothelin (ET) are reduced compared to responses of non-COL coronary arteries. The objective of this study was to determine whether altered Cam responses underlie these contrasting differences in contractile responsiveness of COLs. To permit direct correlation between Cam and contractile tension, we simultaneously measured Cam and contractile responses to VP (100 nM) and ET (0.330 nM) in near-resistance ( ≈ 200μm ID) COL and non-COL coronary arteries using a specially designed microvessel myograph and fura-2 microfluorometry techniques. Canine coronary arteries were isolated 4 mo after placement of an ameroid occluder around the proximal left circumflex coronary artery. VP-induced Cam and contractile responses were increased in parallel in COL arteries compared to responses in non-COL arteries (p < 0.05). Contractile responses to ET were significantly attenuated in COL arteries; however, Cam responses to ET were not significantly different in COL and non-COL arteries. Parallel enhancement of Cam and contractile responses to VP in COL arteries suggests increases in VP receptor number, affinity, and/or coupling mechanisms in COL smooth muscle. In contrast, the dissociation between Cam and contractile responses to ET in COL arteries indicates alterations in Cam sensitization mechanisms coupled to ET receptors in COL smooth muscle.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology