Hemodynamics and sodium balance in conscious sodium-depleted rats

The objective of this paper was to study the hemodynamics (mean arterial pressure, cardiac output, total peripheral resistance, stroke volume and heart rate) of conscious rats submitted to 6 days of sodium depletion. Sodium balance of sodium-depleted rats on a low-sodium diet (0.1 mEq/day) associated with furosemide (10 mg/kg, ip on the first and fifth day) for 6 days indicated that the animals were studied under a negative sodium balance on the sixth day. The overactivity of the renin-angiotensin system in sodium-depleted rats was demonstrated by the fall in mean arterial pressure (15 +/- 2 vs 0.5 +/- 1 mmHg in sodium-depleted and control rats, respectively), after blocking the converting enzyme with BPP9a (SQ 20881) and also by evaluating plasma renin activity (10 +/- 8 vs 3.0 +/- 0.6 ng AI ml-1 h-1 in sodium-depleted and control rats, respectively). Thermodilution measurements showed that the cardiac output of sodium-depleted animals was reduced by 35% (29 +/- 2 vs 45 +/- 4 ml min-1 100 g-1 for sodium-depleted and control rats, respectively), with partial compensation by a 37% increase in total peripheral resistance (3.7 +/- 0.3 vs 2.7 +/- 0.2 PRU for sodium-depleted and control rats, respectively), resulting in an 11% decrease in mean arterial pressure (104 +/- 5 vs 117 +/- 3 mmHg for sodium-depleted and control rats, respectively).