Autoradiographic Localization and Characterization of Angiotensin II Receptors: DISCUSSION(6)


This is in accordance with previous findings. In the present study, enzymatically inactive renin (prorenin) was not determined. In an earlier study, however, no prorenin was detected in the bovine placenta. This is in contrast to the human placenta, which—withthekidney—is amain source of the increased prorenin in the plasma during pregnancy. The active renin concentration is the rate-limiting factor for the formation of Ang I, which is rapidly converted to Ang II by the ubiquitous angiotensin-converting enzyme. The finding that active renin was very low or undetectable in the bovine placenta indicates a low formation rate of Ang II in this tissue. Other enzymes, however, are capable of forming angiotensin from angiotensin-ogen. In the present study, the specific renin inhibitor remikiren abolished all formation of Ang I in the renin assay, indicating that no other Ang I-forming enzymes are present in the bovine placenta. ventolin inhaler

In conclusion, all parts of the bovine placenta and fetal membranes contained high densities of Ang II receptors. AT2 receptors were highly expressed in the fetal part of the placenta, whereas AT1 receptors predominated in the maternal part. No changes in the pattern of distribution of the Ang II receptors were found throughout gestation. It is suggested that Ang II exerts an effect on regulatory as well as growth processes in these tissues.

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