Abstract
Angiotensin I (AI) is rapidly converted to angiotensin II (AII) during a single transpulmonary passage. The enzyme responsible for this hydrolysis, angiotensin-converting enzyme (ACE), is present in small amounts in lungs of newborn animals. Inasmuch as ACE is the final catalytic component of the renin-angiotensin system, and since fetal plasma renin activity increases with advancing gestational age, it was of interest to determine the prenatal development of converting enzyme activity in lungs of fetal rats. ACE activity was measured in vitro by virtue of its ability to generate hippuric acid by hydrolysis of the AI-homologue hippuryl-L-histidyl-L-leucine (HHL). Hippuric acid was extracted from the reaction mixture and quantitated spectrophoto-metrically. ACE activity was first detectable in fetal lungs at 18 days of gestation and increased thereafter until birth (day 21 of gestation). The in utero development of ACE activity was paralleled by increases in fetal lung weight and protein content. The affinity of converting enzyme from fetal lung for HHL (Km = 2.0 mM) was similar to that of the adult enzyme, suggesting that the increase in ACE activity was due to increased enzyme content rather than further activation of pre-existing enzyme. This antenatal increase in ACE activity may play an important role in the maturation of the renin-angiotensin system which has been implicated in the regulation of body fluid homeostasis during the perinatal period.
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Wallace, K., Hook, J. & Bailie, M. 221 PRENATAL DEVELOPMENT OF ANGIOTENSIN-CONVERTING ENZYME ACTIVITY IN RAT LUNGS. Pediatr Res 12 (Suppl 4), 400 (1978). https://doi.org/10.1203/00006450-197804001-00226
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DOI: https://doi.org/10.1203/00006450-197804001-00226