Hypertension and Nephrolithiasis: Tubular Renal Disease?

Abstract

Introduction: Patients with mild renal failure are characterised by a marked increase in muscle sympathetic neural outflow. No data are available on whether this adrenergic activation 1) is generalised to the whole circulation and 2) is related to the metabolic (insulin resistance) and cardiac (left ventricular hypertrophy) abnormalities frequently detected in this condition. Methods: In 16 patients (8 females, 8 males, age 60.4+2.4 yrs, mean ± SEM) with mild renal failure (creatinine clearance ranging from 36 to 66 ml/min), we measured beat-to-beat arterial blood pressure (Finapres), heart rate (EKG, HR) and efferent postganglionic muscle sympathetic nerve traffic (microneurography, MSNA) during a 20 min resting period. Measurements also included 1) glucose and insulin assay (radioenzymatic method) and HOMA index calculation, 2) echocardiographic assessment of left ventricular mass index (LVMI) and 3) microneurographic recording of skin sympathetic nerve traffic (SSNA). Results: For similar blood pressure values, patients with mild renal failure displayed MSNA values significantly greater than those found in age-matched controls, both when expressed as bursts incidence over time (51.3±2.8 vs 38.4±3.5 bs/min, p±3.2 vs 54.8±5.6 bs/100 hb, p controls (HR: 72.2±3.1 vs 70.5±1.4 b/min, p=NS; SSNA: 12.3±1.3 vs 14.4±1.8 bs/min, p=NS). Furthermore, in renal failure patients with (n=6) and without (n=10) insulin resistance (HOMA index: 5.5±1.8 vs 1.4±0.2 a.u., p±3.3 vs 70.5±4.2 bs/100 hb). Similarly, renal failure patients with (n=8) and without (n=8) left ventricular hypertrophy (LVMI: 130.5±5.3 vs 93.1±2.8 g/m 2 , p±4.0 vs 73.9±4.1 bs/100 hb).Conclusions: Thus in mild renal failure sympathetic activation does not appear to be generalised to the whole circulation, the cardiac and the skin district not displaying the adrenergic overdrive seen in the muscle circulation. They also show that, in contrast to what found in other pathologic states, sympathetic activation is not related to insulin resistance or potentiated by left ventricular hypertrophy.