Endothelium, Mechanical Compliance, and cGMP Content in the Carotid Artery from Spontaneously Hypertensive Rats

Abstract

An experimental model of in situ isolated carotid arteries has been used to evaluate the static mechanical properties of the arterial wall in 12-week-old Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). The effects of endothelium removal on the carotid compliance (CC) were compared to the effects of total abolition of the vascular smooth muscle tone by potassium cyanide (KCN). CC measured for pressures ranging from 50 to 175 mm Hg had maximal values (0.22 +/- 0.07 and 0.13 +/- 0.03 microliters/mm Hg, respectively, for WKY rats and SHRs, p < 0.001) for pressure close to the mean arterial pressure (operating pressures). Operating values of CC were increased by 35 and by 45% in WKY rats and SHRs, respectively, after KCN poisoning (p < 0.01). The endothelium removal induced a significant increase in CC compared to their control values (+37%, p < 0.01 and +25%, p < 0.01, respectively, in WKY rats and SHRs). With intact endothelium, carotid cGMP level was higher in SHRs than in WKY rats (30.3 +/- 3.7 vs. 19.7 +/- 2.3 fmol/mg tissue, p < 0.02). After endothelium removal, tissue cGMP was reduced by 28% in WKY rats (p < 0.02) and by 90% in SHRs (p < 0.001). The present results suggest that the mechanical properties of the wall of the carotid artery are endothelium-dependent. CC for operating pressure was significantly increased after endothelium removal in both strains. Furthermore, the cGMP pathway seems to be more activated in the carotid wall from SHRs than from WKY rats.(ABSTRACT TRUNCATED AT 250 WORDS)