ATRIAL-NATRIURETIC-PEPTIDE IS PRODUCED LESS IN THE INTERCAVAL SINUS THAN IN THE PECTINATED RIGHT ATRIUM

To explain the lower atrial natriuretic peptide concentrations after t otal cavopulmonary connection than after the Fontan procedure, a prosp ective study was carried out in seven rats to count the specific granu les of atrial natriuretic peptide by electronmicroscope. After fasting from water for 12 days, the quantity of specific granules in the righ t atrial appendage (pectinated part), intercaval sinus (smooth part), and superior vena cava were counted. The number of specific granules p resent in the pectinated part of right atrium was 97 +/- 19 in 20 cell s, while in the intercaval sinus it was 23 +/- 19 (mean +/- SD). The d ifference was significant statistically (p < 0.0001). No granule was p resent in the superior vena cava. We conclude that the granularity of atrial natriuretic peptide is less in the intercaval sinus than the pe ctinated part of the right atrium.