Impaired atrial natriuretic factor systemic clearance contributes to its higher levels in uremia

To evaluate the interaction between plasma levels and the systemic uptake of atrial natriuretic factor (ANF) with thyroid hormone levels during acute renal failure (ARF), seven groups of rats were analyzed: Group 1, Controls (C); Group 2, ARF; Group 3, filtering kidney with uremia; Group 4, ARF with thyroxine (T4) supplement (ARF + T4); Group 5, thyroidectomy (Tx); Group 6, ARF on Tx rats (Tx + ARF); Group 7, Tx + ARF supplemented with T4 (Tx + ARF + T4). Plasma creatinine (Cr), urea, T4, blood volume, and ANF were measured; ANF half-life (ANF t1/2; expressed in seconds) was calculated. Rats with ARF developed uremia (Cr, 377 +/- 58 versus 41 +/- 5 mumol/L), significant reduction in T4 (40 +/- 4 versus 89.2 +/- 6 nmol/L). elevation of ANF (287.7 +/- 35 versus 60.9 +/- 8 fmol/mL), and lengthening of ANF t1/2 (69.7 +/- 8 versus 37.2 +/- 6 s) compared with C (P less than 0.01). T4 supplements to ARF rats resulted in a lesser degree of uremia (Cr, 283 +/- 27; P less than 0.05) and normalization of ANF t1/2 (31.4 +/- 5); however, ANF levels remained higher than C (100.4 +/- 11.4 versus 60.9 +/- 8; P less than 0.01). Tx by itself did not change either parameter. The filtering kidney with uremia group developed mild uremia (Cr, 199 +/- 8), T4 fell (58 +/- 8), ANF levels rose (83.4 +/- 5.4), and ANF t1/2 was prolonged (54.5 +/- 12). Tx before ARF doubled the ANF level and lengthened ANF t1/2 similarly than in ARF. T4 addition (Tx + ARF + T4) normalized ANF t1/2 (29.8 +/- 3) in spite of a persistently high ANF (145.7 +/- 21). Blood volume did not change in any group.(ABSTRACT TRUNCATED AT 250 WORDS)