Changes in the renin-angiotensin system, exchangeable body sodium, and plasma and atrial content of atrial natriuretic factor during evolution of chronic renal failure in the rat.

Abstract

The remnant kidney model of progressive renal failure in the rat was used to assess the relationships between the renin-angiotensin system, exchangeable body sodium, and both plasma concentration and atrial content of atrial natriuretic factor (ANF) measured sequentially over 4 weeks. Following subtotal nephrectomy plasma creatinine (mumol/L) rose from 40 +/- 6 (sham) to 107 +/- 24 (P less than 0.05) at 1 week, and rose further to 124 +/- 20 (P less than 0.05) by 4 weeks. Plasma renin activity (nanograms of angiotensin I/mL/min) rose from 4.5 +/- 0.5 to 11.8 +/- 2.8 (P less than 0.05) at 1 week, but was suppressed by 4 weeks to 2.2 +/- 0.3 (P less than 0.001). Plasma angiotensin II (pg/mL) was 52 +/- 2 (sham), 117 +/- 20 at 1 week (P less than 0.05) and 51.3 at 4 weeks. Exchangeable sodium (mmol/kg) rose progressively from 43.2 +/- 5 (before surgery) to 48.6 +/- 0.9 at 1 week and 50.8 +/- 2.2 at 4 weeks. Plasma atrial natriuretic factor (ANF) (pg/mL) rose progressively from 114 +/- 6 (sham) to 248 +/- 31 (P less than 0.01) at 1 week and 456 +/- 78 at 4 weeks (P less than 0.01). Atrial ANF content fell as the plasma concentration rose. In the remnant kidney model of progressive renal failure there was a progressive increase in exchangeable body sodium and plasma atrial natriuretic factor, with reciprocal changes in atrial ANF content suggesting that ANF secretion rate was increased. Initially the renin-angiotensin system was stimulated, but later it was suppressed.