Endothelial and smooth muscle properties of coronary and mesenteric resistance arteries in spontaneously hypertensive rats compared to WKY rats.

To investigate if the functional alterations observed in resistance arteries of spontaneously hypertensive rats (SHRs) were also present at the coronary level, in vitro experiments were performed in mesenteric resistance arteries (MRA) and in right (RIC) and left interventricular coronary (LIC) arteries taken from 15-25-week-old SHR and age-matched Wistar Kyoto rats WKYs. Using a passive extension protocol, internal diameters corresponding to 100 mmHg intraluminal pressure (D100) were determined and vessels were set up to a normalized internal diameter (0.9 D100). SHR mesenteric resistance arteries had a significantly smaller diameter compared to WKY arteries, whereas both types of SHR coronary arteries had a greater diameter compared to those of WKY rats. In arteries in the absence of contracting agonist, nitro-L-arginine (NOLA, 100 microM) induced a progressive rise in basal tone, which could be reversed by subsequent addition of L-arginine (100 microM) but not D-arginine (100 microM). When expressed as percent of maximal contractions induced by agonists (noradrenaline, NA [10 microM] in MRA; serotonin, 5-HT [10 microM], in RIC and LIC), these contractions were significantly stronger in WKY compared to SHR coronary and mesenteric resistance arteries. In NA-precontracted MRA and 5HT-precontracted coronary arteries in the presence of indomethacin (10 microM), the magnitude of acetylcholine-induced maximal relaxations (expressed as percent of maximal contractions induced by agonists) was greater in WKY compared to SHR arteries. After a 30-min incubation period, NOLA (100 microM) completely inhibited relaxations induced by acetylcholine (0.01-10 microM) in all types of precontracted arteries.(ABSTRACT TRUNCATED AT 250 WORDS)