Phasic plasma atrial natriuretic polypeptide changes in DOCA-salt hypertensive rats

We determined plasma and cardiac immunoreactive atrial natriuretic polypeptide (ir-ANP) levels in rats treated with deoxycorticosterone acetate (DOCA) and sodium chloride for 1, 7, and 28 days. Systolic blood pressure of DOCA-salt rats began to increase from the 7th day and reached 191 +/- 7 mmHg at the 28th day. One day after treatment with DOCA-salt, plasma levels of ir-ANP were increased compared to that of control rats. This was accompanied by decreased cardiac ir-ANP content. However, at the 7th day of DOCA-salt treatment, both plasma and cardiac ir-ANP levels of DOCA-salt rats were not different from those of control animals. At the 28th day, DOCA-salt rats had high plasma ir-ANP levels and no significantly different cardiac ir-ANP content compared to the controls. These data suggest that there are time-related changes in plasma ANP concentration during the development of DOCA-salt hypertension and higher plasma ANP levels might not necessarily be associated with a decreased cardiac ANP content.