Endothelin A Receptor Blockade Prevents Capillary/Myocyte Mismatch in the Heart of Uremic Animals

In the heart of uremic animals and patients, the number of capillaries per volume of myocardium is reduced. Immunohistochemical studies demonstrated increased cardiac endothelin-1 (ET-1) expression in the left ventricle of uremic animals. Therefore, whether treatment with a selective ET A -receptor antagonist prevented such capillary-myocyte mismatch was investigated. Twenty-four h after subtotal nephrectomy, rats were left untreated or started on treatment with the ET A -receptor antagonist LU 135252 (20 mg/kg per d) and with the angiotensin-converting enzyme (ACE) inhibitor trandolapril (0.3 mg/kg per d), respectively. BP was monitored by telemetry. Myocardial capillary length density was analyzed by stereologic techniques that avoid anisotropy artifacts. In addition, cardiac ET-1 protein and mRNA were measured using immunohistochemistry, in situ hybridization, and quantitative reverse transcription—PCR. Changes in cardiac ET A -and ET B -PCR. receptor mRNA were measured using reverse transcription—PCR. Fifteen wk after subtotal nephrectomy, significantly reduced left ventricular capillary length density (3307 ± 535 mm/mm 3 ) was found compared with sham-operated controls (3995 ± 471 mm/mm 3 ); this was also seen in animals that were treated with trandolapril (3503 ± 533 mm/mm 3 ) but not in animals that were treated with LU 135252 (3800 ± 303 mm/mm 3 ). The results support a role of ET-1 in the genesis of left ventricular capillary/myocyte mismatch in uremia.