Increased sympathetic activity contributes to hypertension in patients with chronic renal disease. ACE inhibition controls hypertension and decreases sympathetic hyperactivity.

Abstract. The hypothesis that in hypertensive patients with renal parenchymal disease sympathetic activity is "inappropriately" elevated and that this overactivity is a feature of renal disease and not of a reduced number of nephrons per se is addressed. Fifty seven patients with renal disease (various causes, no diabetes, all on antihypertensive medication) were studied, age range 18 to 62, creatinine clearance 10 to 114 ml/min per 1.73 m 2 . Antihypertensives were stopped, but diuretics were allowed, to prevent overhydration. Matched control subjects were also studied. The effect of changes in fluid status was examined in seven patients while on and after stopping diuretics and in eight control subjects while on lowand high-sodium diet. Seven kidney donors were studied before and after unilateral nephrectomy. Sympathetic activity was quantified as muscle sympathetic nerve activity (MSNA) in the peroneal nerve. Mean arterial pressure, MSNA, and plasma renin activity were higher in patients than in control subjects, respectively (115 Ϯ 12 and 88 Ϯ 11 mmHg, 31 Ϯ 15 and 18 Ϯ 10 bursts/min, and 500 [20 to 6940] and 220 [40 to 980] fmol/L per s; P Ͻ 0.01 for all items). Extracellular fluid volume (bromide distribution) did not differ. Seven patients were studied again after stopping diuretics. MSNA decreased from 34 Ϯ 18 to 19 Ϯ 18 bursts/min (P Ͻ 0.01). Eight healthy subjects were studied during low-and high-sodium diet. MSNA was 26 Ϯ 12 and 13 Ϯ 7 bursts/min (P Ͻ 0.01). The curves relating extracellular fluid volume to MSNA were parallel in the two groups but shifted to a higher level of MSNA in the patients. In the kidney donors, creatinine clearance reduced by 25%, but MSNA was identical before and after donation. It is concluded that in hypertensive patients with renal parenchymal disease, sympathetic activity is inappropriately high for the volume status and that reduction of nephron number in itself does not influence sympathetic activity.

Abstract. The aim of this study was to compare the effects on BP and sympathetic activity of chronic treatment with an angiotensin (Ang)-converting enzyme (ACE) inhibitor and an AngII receptor blocker in hypertensive patients with chronic renal failure (CRF). In ten stable hypertensive CRF patients (creatinine clearance, 46 Ϯ 17 ml/min per 1.73 m 2 ), muscle sympathetic nerve activity (MSNA), plasma renin activity (PRA), baroreceptor sensitivity, and 24-h ambulatory BP were measured in the absence of antihypertensive drugs (except diuretics) after 6 wk of enalapril (10 mg orally) and after 6 wk of losartan (100 mg orally). The order of the three phases was randomized. Normovolemia was controlled with diuretics and confirmed with extracellular fluid volume measurements throughout the study. Both enalapril and losartan reduced MSNA (from 33 Ϯ 10 to 27 Ϯ 13 and 27 Ϯ 13 bursts/min, respectively; P Ͻ 0.05) and average 24-h BP (from 141 Ϯ 8/93 Ϯ 8 to 124 Ϯ 9/79 Ϯ 8 and 127 Ϯ 8/81 Ϯ 9 mmHg; P Ͻ 0.01). PRA was not different during the treatments. The change in BP and the change in MSNA during the treatments were correlated (r ϭ 0.70 and r ϭ 0.63, respectively; both P Ͻ 0.05). Baroreceptor sensitivity was not affected by the treatments. This is the first study to compare the effects of ACE inhibition and AngII blockade on MSNA. In hypertensive CRF patients, enalapril and losartan equally reduced BP and MSNA. Differences in modes of action of the two drugs did not result in differences in effects on MSNA, supporting the view that AngII-mediated mechanisms contribute importantly in the pathogenesis of sympathetic hyperactivity in these patients.Sympathetic hyperactivity in chronic renal failure (CRF) is caused by mechanisms arising in the failing kidneys (1). The renin system is often activated in hypertensive patients with CRF. There is clear evidence that high circulating angiotensin II (AngII) levels can stimulate central sympathetic outflow by a direct effect on the vasomotor center in the brain stem, which in humans can be quantified as increased muscle sympathetic nerve activity (MSNA) (2). We showed that MSNA is increased in patients with CRF and that this hyperactivity was reduced by chronic angiotensin-converting enzyme (ACE) inhibition (3). These findings support the idea that AngII is involved in the pathogenesis of the sympathetic hyperactivity. However, ACE inhibition did not completely normalize the MSNA in these patients. There is increasing evidence that sympathetic hyperactivity contributes to the cardiovascular risk profile, not only by its effect on BP, but also independent of this effect (4).The hypothesis in the present study was that AngII receptor blockade in an equally effective antihypertensive regimen more effectively reduces the sympathetic hyperactivity than ACE inhibition. AngII receptor blockers are well accepted as antihypertensive agents in patients with CRF (5-7). Their BP lowering effect is comparable to that of ACE inhibitors (7,8). However, although both classes of drugs primarily interf...

We conclude that tacrolimus given during 2 weeks in the currently advised dosage has no unfavorable effects on renal hemodynamics and blood pressure in healthy individuals. The use of tacrolimus in organ transplant recipients may in the long-term lead to better renal function and less cardiovascular morbidity than the use of cyclosporine.

Sympathetic overactivity plays a role in the acute hypertensive action of cyclosporine. Cyclosporine given during 2 weeks increases blood pressure and suppresses MSNA, possibly by volume retention. Tacrolimus, in the presently applied dosages, does not cause hypertension or sympathetic overactivity. However, sustained tacrolimus also suppresses sympathetic activity, the reason of which is unclear.