Angiotensin receptor antagonist improves cardiac reflex control of renal sodium handling in heart failure

In rats with congestive heart failure, type 1 angiotensin IT receptor antagonist treatment (losartan) decreases basal renal sympathetic nerve activity and improves arterial baroreflex regulation of renal sympathetic nerve activity This investigation examined the effect of losartan on cardiac baroreflex regulation of renal sympathetic nerve activity and renal sodium handling in rats with congestive heart failure. Losartan treatment decreased arterial pressure from 120 +/- 3 to 93 +/- 5 mmHg and increased the afferent (from 0.95 +/- 0.21 to 2.22 +/- 0.42% Delta afferent vagal nerve activity/mmHg mean right atrial pressure, P < 0.05) and overall gain (from -1.14 +/- 0.19 to -4.20 +/- 0.39% Delta renal sympathetic nerve activity/mmHg mean right atrial pressure, P < 0.05) of the cardiac baroreflex. During isotonic saline volume loading, urinary sodium excretion increased from 2.4 +/- 0.8 to 10.5 +/- 1.3 mu eq/min in vehicle-treated rats (excretion of 52 +/- 340 of the load) and from 3.0 +/- 1.0 to 15.1 +/- 1.8 mu eq/min in losartan-treated rats (excretion of 65 +/- 4% of the load, P < 0.05). When rats were changed from a low- to a high-sodium diet, cumulative sodium balance over 5 days was 7.8 +/- 0.6 meg in vehicle-treated rats and 4.2 +/- 0.4 meq in losartan-treated rats (P < 0.05). In congestive heart failure, losartan treatment improved cardiac baroreflex regulation of renal sympathetic nerve activity, which was associated with improved ability to excrete acute and chronic sodium loads.