Regional systemic ANP differences in fetal lambs: role of coronary sinus outflow distribution

Although it is known that the atrial natriuretic peptide (ANP) level in right ventricular (RV) blood supplying the caudal part of the fetus is greater than in left ventricular blood perfusing the cephalic part of the fetus, the extent to which any preferential passage of coronary sinus blood into the right ventricle contributes to regional differences between ANP levels in fetal cephalic and caudal arteries is unknown. To address this question, experiments were performed in eight late-gestation fetal lambs, 3-7 days after catheters were inserted into the left atrium, major arteries and veins, and coronary sinus (via the left hemiazygous vein). The plasma ANP level in the abdominal aorta (171 +/- 33 pg/ml) was higher than in the carotid artery (103 +/- 15 pg/ml; P < 0.05), and both were lower than in the coronary sinus (736 +/- 89 pg/ml; P < 0.005). The coronary sinus outflow, measured with radioactive microspheres injected into the hemiazygous vein, was preferentially distributed to the right ventricle (94.7 +/- 1.3%) and thence to the abdominal aorta (89.5 +/- 1.6%). This streaming of the coronary sinus outflow contributed 13.3 +/- 0.9 and 1.4 +/- 0.4 pg/ml to ANP levels in the abdominal aorta and carotid artery, respectively, and thereby accounted for 11.9 +/- 0.9 pg/ml of the abdominal aorta-carotid artery ANP difference of 68 +/- 25 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)