Atrial natriuretic factor release during angiotensin II infusion in right and left atrial appendectomized rats

The effect of selective right or left atrial appendectomy on atrial natriuretic factor (ANF) release was studied in the rat to compare the relative contribution of each atrium in a situation of increased afterload. Sham-operated or right (RAA) or left (LAA) atrial appendectomized conscious rats were infused (intravenously) for 60 min with a pressor dose of angiotensin II (Ang II; 600 ng/kg per min). All groups presented a significant and similar elevation of mean arterial pressure (MAP) and left ventricular end-diastolic pressure (LVEDP). No change in central venous pressure (CVP) was noted in the LAA group, whereas a small, transient rise was observed in the two other groups. The Ang II-induced release of ANF C-terminal was blunted in the RAA group (P less than 0.01 versus sham) and more so in the LAA group (P less than 0.001 versus sham). Atrial natriuretic factor N-terminal release was blunted only in the LAA group (P less than 0.05 versus sham). No correlation was found between CVP and ANF in any group. The relationship between LVEDP and ANF in the sham-operated controls became weaker in the LAA group and was lost in the RAA group. We conclude that both atria play a role in the ANF release induced by a vasoconstrictor agent, but changes in left heart haemodynamics may be the first to be involved in the response to an increased afterload.