Effect of one-kidney, one clip hypertension on the structure and function of porcine intramyocardial small arteries

Objective : To determine the influence of experimental hypertension on the structure and function of porcine coronary small arteries. Methods : Miniature pigs underwent partial left renal artery constriction and contralateral nephrectomy. Blood pressures were recorded, using indwelling carotid artery catheters. After 4 weeks the pigs were killed, the heart was removed and subepicardial third-order branches of the left anterior descending artery were dissected and mounted in a myograph for morphological and functional assessment. Results : Final mean +SEM systolic and diastolic blood pressures were, respectively, 197±9 and 142±7mmHg (n=21) for the hypertensive pigs and 125±4 and 80 ± 4 mmHg (n = 11) for the sham-operated control pigs. Hypertension was associated with significant left ventricular hypertrophy. The media thickness : lumen diameter ratio was increased significantly in hypertensive intramyocardial small arteries, caused mainly by remodelling (remodelling index 92%) rather than by medial growth. Maximal contractile responses to potassium and acetycholine were significantly depressed in the arteries from hypertensive pigs, whereas endothelium-dependent relaxation responses to bradykinin, substance P and serotonin were not significantly influenced by hypertension. Conclusions : These results demonstrate that even short-term hypertension induces both structural and functional changes in left ventricular intramyocardial small arteries.