HIGH-DENSITIES OF ANGIOTENSIN-II SUBTYPE-2 (AT(2)) RECEPTORS IN THE PORCINE PLACENTA AND FETAL MEMBRANES

The present study was undertaken in order to characterize and determin e angiotensin (Ang) II receptors and renin in the porcine placenta and fetal membranes. High densities of Ang II receptors of subtype 2 (AT( 2) receptors) were demonstrated in all parts of the placenta and fetal membranes throughout gestation. AT(1) receptors (subtype 1) were only found in the first part of the gestation and only in the allantochori on-endometrium at low densities. The total Ang II receptor density was increased in the allantochorion-endometrium in the last stage of gest ation. Except for this finding the Ang II receptor density did not var y during gestation. Some of the highest receptor densities were found in the allantoamnionic membrane. The Ang II receptor densities did not correlate with the duration of the gestation in any part of the place nta. Enzymatically active renin was found in all parts of the porcine placenta and fetal membranes in concentrations similar to those found earlier in the blood plasma. The renin concentrations did not correlat e with the Ang II receptor densities or the duration of the gestation in any part of the placenta. Compared with the human placenta, where t he Ang II receptors are almost exclusively AT(1) receptors and low rec eptor densities are found in the fetal membranes, the present results indicate profound species differences in the expression and function o f the renin-angiotensin system in the placenta and fetal membranes. (C ) 1996 W. B. Saunders Company Ltd