Synthesis and secretion of atrial natriuretic factor during chronic hypoxia: a study in the conscious instrumented rat.

1. To investigate the mechanisms leading to enhanced synthesis and release of atrial natriuretic factor during chronic hypoxia, we measured immunoreactive plasma atrial natriuretic factor, blood gases, packed cell volume, pulmonary artery pressure and systemic artery pressure in male Sprague-Dawley rats exposed to 1, 2 or 3 weeks of normobaric hypoxia. Rats were implanted with pulmonary and carotid artery catheters and studied conscious, 23 h after return to hypoxia. 2. The concentration of atrial natriuretic factor messenger RNA was measured in the right and left ventricular free walls of rats exposed to 3 weeks of hypoxia and in normoxic control rats. 3. There was a trend for plasma atrial natriuretic factor to increase with the duration of exposure to hypoxia but only the 3-week hypoxic rats had a significantly higher level (1080 +/- 193 pg/ml) than the normoxic control rats (318 +/- 46 pg/ml, P less than 0.05, mean +/- SEM). When all the data from normoxic and hypoxic rats were considered together, plasma atrial natriuretic factor was positively correlated with packed cell volume (r = 0.66, P less than 0.001), pulmonary artery pressure (r = 0.68, P less than 0.002), and the index of right ventricular hypertrophy (r = 0.54, P less than 0.01), but after analysis of partial correlation, packed cell volume was the only independent contributing factor to the variance in the level of plasma atrial natriuretic factor (r2 = 0.24).(ABSTRACT TRUNCATED AT 250 WORDS)