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To determine the influence of experimental hypertension on the structure and function of porcine coronary small arteries.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.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.These results demonstrate that even short-term hypertension induces both structural and functional changes in left ventricular intramyocardial small arteries.