"The aminopeptidases which degrade hormones produced from fetus".


In this blog I will show you the placental aminopeptidases in both placenta and maternal blood which act as a barrier between fetus and mother with bioactive hormones produced from fetus.

Looking back the history of hormonal research, it is reminded that the research of the controlling factor of peptide hormones namely degrading substances has started much earlier than the hormone receptors. In addition this factor was studied in the obstetrics. The biological activity with vasoactive peptide hormones such as vasopressin and angiotensin and utero-tonic hormone, oxytocin were founded firstly in the extracted substances from animal brain. From the nineteen thirties they were synthesized chemically.   

Do you know about amino acids?  The protein is composed of amino acids. The peptide is named for the substances coupled with around 10 amino acids. The bioactive peptide hormones are consisted of less than 10 amino acids. While the administration of the extracted substances from animal brain have the biological activity in the animal, it has no biological activity in pregnancy animal. These observation have shown the existence of degrading activity of bioactive peptide hormones in pregnancy blood. The research with oxytocin and vasopressin degrading enzyme and angiotensin degrading enzyme started since  around 1940 by gynecologists in USA. The angiotensinase research was originated in the following experiment: the blood pressure was observed in pregnant imprisoned women by administration of angiotensin. While change of blood pressure was not observed in pregnant women at term, the marked rise of blood pressure by administration of angiotensin in puerperal women at 7 days after delivery. The magnitude of the rise in puerperal women by administration of angiotensin was decreased toward approaching delivery day. This observation show the existence of angiotensinase in pregnant women and the mechanisms of refractoriness against angiotensin in pregnant women which is well known and believed to be the probable cause of preeclampsia. While normal pregnant women have the refractoriness against angiotensin, preeclampsia patients lost this unique phenomenon and show the similar rise of blood pressure to normal men and non-pregnant women by administration of angiotensin.

From nineteen thirties synthetic oxytocin was started to be used as a labor pain inducing agent in USA and in Japan after the Pacific War. I will ask  you one question. I have shown the existence of oxytocinase in pregnant women suggesting disappearance of oxytocin activity by administration of this substance. Why does oxytocin act as a labor pain inducing agent?  To tell the truth utero-tonic activity of oxytocin is dramatically changed at the stage of pregnancy. Since it works dramatically, it results in uterine rupture according to the stage of pregnancy and also to its doses. On the other hand placental leucine aminopeptidase (P-LAP) namely oxytocin and vasopressin degrading enzyme produced from placenta increases with advancing pregnancy in the blood. However P-LAP stops its increase before 10 days before the onset of labor. Therefore at this stage oxytocin is very effective for inducing the labor pain. You might be able to get the image of the mechanisms of the onset of labor and also preeclampsia by this blog. Thank you