Regional systemic anp differences in fetal lambs: role of coronary sinus outflow distribution. Smolich, Joseph J., Robyn L. Woods. Institute of Reproduction and Development, Monash University, Clayton, Victoria, Australia; Baker Medical Research Institute, Prahran, Victoria, Australia
APStracts 2:0095H, 1995.
Although it is known that the 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 8 late-gestation fetal lambs, 3-7 days after insertion of catheters 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 x ml -1, was higher than in the carotid artery, 103 +/- 15 pg x ml -1 (P < 0.05), and both were lower than in the coronary sinus, 736 +/- 89 pg x ml -1 (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 pg x ml -1 and 1.4 +/- 0.4 pg x ml -1 to ANP levels in the abdominal aorta and carotid artery respectively, and thereby accounted for 11.9 +/- 0.9 pg x ml -1 of the abdominal aorta-carotid artery ANP difference of 68 +/- 25 pg x ml -1. We conclude that, in fetal sheep, 1) the coronary sinus outflow contains high plasma levels of ANP; 2) due to preferential passage of the coronary sinus outflow into the right ventricle, most of the ANP present in coronary sinus blood enters the abdominal aorta; 3) preferential passage of coronary sinus-derived ANP into the abdominal aorta accounts for <20% of the difference between ANP levels in cephalic and caudal arteries; 4) most of the cephalo-caudal arterial ANP difference is probably related to secretion of ANP directly into the right heart chambers. 

Received 28 July 1994; accepted in final form 3 March 1995.
APS Manuscript Number H664-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.