Recent studies showed that coronary reactivity exhibits agonist-selective alterations in hypertensive rats. This study examined contractile and Ca responses of coronary artery rings (COR) from normotensive control-salt rats (CSR) and aldosterone-salt hypertensive rats (AHR). Isometric tension was measured with a microvessel myograph. COR from AHR exhibited smaller contractions to KCI (80 mM), serotonin (5-HT, 10 uM) and prostaglandin F2a (PGF2a, 100 uM). Maximal contractions were 3.0±0.4mN/mm, 3.4±0.4 mN/mm and 3.8±0.6 mN/mm in CSR and 1.1±0.3mN/mm, 1.1±0.4mN/mm and 0-9 mN/mm in AHR (p<0.05,n=5-7). Concentration-response curves of the contractions induced by 5-HT and PGF2o were also shifted significantly to the right in AHR. Average myoplasmic Ca concentration (CaJ of COR smooth muscle was monitored with fura-2. The Cam response to KCI was smaller in AHR than CSR (46±9 nM vs. 141±13 nM, p<0.05, n=29-33). However, the Cam responses to maximal concentration of 5-HT (10 μM) were similar between CSR and AHR (43±9 nM vs. 39±8 nM, n=18-21). Therefore, while the attenuated contractile response to depolarization is matched by a decreased Cam response, an agonist-dependent dissociation of Cam regulation and contraction appears to exist in coronary arteries of hypertensive rats. (SupportNIH grants RCDA HL02872, HL15852; AHA grant 93011900: and a postdoctoral fellowship from AHA Missouri-Affiliate).
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology