Effect of atrial natriuretic peptide on vascular permeation in the ovine fetus

To study the effect of atrial natriuretic peptide (ANP) on vascular permeation of albumin in the fetus, ANP (167-600 ng/min) was infused into eight ovine fetuses and saline vehicle was infused into eight twin controls (gestational age 127 +/- 3 d) over a 50-min period. Using two different radiolabeled albumin markers, we determined the tissue to blood isotope ratio (TBIR), an index of albumin permeation, and the albumin clearance. Although ANP had no hemodynamic effect, a marked increase in the hematocrit was observed in ANP-infused fetuses compared with initial values (0.37 +/- 0.04 vs 0.42 +/- 0.04, p < 0.005) but was unchanged in the twin fetuses receiving saline vehicle (0.35 +/- 0.03 versus 0.35 +/- 0.02). TBIR and albumin permeation were increased in combined tissues of ANP-infused fetuses compared with saline controls (TBIR: 1.49 +/- 0.58 versus 1.29 +/- 0.3, p < 0.001; albumin clearance: 1091 +/- 1279 versus 827 +/- 1464 nL/g/min, p < 0.01). In individual tissues, TBIR was significantly increased in skin (2.88 +/- 0.67 versus 1.55 +/- 0.35, p < 0.02), muscle (1.6 +/- 0.27 versus 1.24 +/- 0.26, p < 0.02), adrenal (1.33 +/- 0.10 versus 1.13 +/- 0.15, p < 0.02), bone (1.67 +/- 0.45 versus 1.20 +/- 0.40, p < 0.02), kidney (1.52 +/- 0.25 versus 1.24 +/- 0.26, p < 0.03), and gut (1.69 +/- 0.20 versus 1.39 +/- 0.34, p < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)