Effect of Microsomal Leucine Aminopeptidase from Human Placenta (microsomal P-LAP) on Pressor Response to Infused Angiotensin II (A-II) in Rat

The role of microsomal placental leucine aminopeptidase (microsomal P-LAP) in the decreased pressor responsiveness to angiotensin II (A-II) in pregnancy was studied. Appreciable amounts of microsomal P-LAP activity were found in rat placenta. The similar dose to the endogenous activity, of human microsomal P-LAP exogenously administered to rats, resulted in significant decrease in the response to A-II. Bestatin, an inhibitor of the microsomal leucine aminopeptidase administered to pregnant rats, enhanced the A-II response. Therefore our present study suggests such refractoriness in response to A-II in pregnancy is due to increased inactivation by the microsomal P-LAP. It was also suggested that prostaglandins were not involved in such refractoriness by the experiments with indomethacin.