Distinct Endothelial Impairment in Coronary Microvessels from Hypertensive Dahl Rats

Abstract

Hypertension has been linked to an impaired dilator function of the coronary microvascular endothelium in vivo. However, the profile and mechanism of this dysfunction remain obscure. Thus, this study compared diameter responses to acetylcholine (ACH), bradykinin (BKN), and substance P (SP) between coronary microvessels (i.d. = 106 +/- 4 micro meter) dissected from left ventricles of normotensive and hypertensive Dahl rats (Dahl-NT and Dahl-HT, respectively). Vessels were cannulated and pressurized on glass pipettes at 80 mm Hg, and internal diameters were monitored by videomicroscopy. Coronary microvessels from Dahl-NT and Dahl-HT showed similar dilator responses to ACH (100 pmol/L to 10 micro mol/L), with maximal diameter increases of 63 +/- 5 micro meter and 63 +/- 7 micro meter, respectively (n = 31,17). However, only vessels from Dahl-NT showed dilator responses to SP (10 fmol/L to 1 nmol/L and BKN (100 fmol/L to 10 nmol/L). All dilator responses persisted after N-nitro-L-arginine (10 micro mol/L) or indomethacin (10 micro mol/L), but were blunted after inhibition of cytochrome P450 by 10 micro mol/L octadecynoic acid (n = 6-8). These results suggest that: (1) coronary microvessels from Dahl-HT show a unique pattern of endothelial impairment, whereby ACH-induced relaxations persist at a time when dilator responses to SP and BKN are severely blunted, and (2) a cytochrome P450 product, rather than nitric oxide or prostacyclin, may partly mediate the vasodilator responses to ACH, SP and BKN. (Hypertension. 1998;31[part 2]:328-334.). © 1998 Lippincott Williams & Wilkins, Inc.