Processing of angiotensin peptides by NG108-15 neuroblastoma x glioma hybrid cell line.

The metabolism of angiotensin (Ang) peptides was studied in NG108-15 neuroblastoma x glioma hybrid cells which express Ang II receptors, renin, dipeptidyl carboxypeptidase A (converting enzyme), as well as Ang I and Ang II. In these experiments, 0.2 nM of either 125I-Ang I or 125I-Ang II was incubated with intact cell monolayers and the medium was analyzed for 125I-products by high performance liquid chromatography. The major product generated from the metabolism of labeled Ang I or Ang II was identified as the amino-terminal heptapeptide Ang-(1-7). N-benzyloxycarbonyl-prolyl-prolinal (ZPP), a specific inhibitor of prolyl endopeptidase, inhibited the formation of Ang-(1-7) from Ang I by 35%. Complete inhibition of Ang-(1-7) generation was attained with p-chloromercuriphenyl-sulfonate, which suggests that a sulfhydryl-containing peptidase other than prolyl endopeptidase is also involved in Ang-(1-7) formation. Ang II was observed to be a minor product resulting from Ang I metabolism. Although the converting enzyme inhibitor enalaprilat (MK-422) significantly reduced Ang II formation, it had no effect on the levels of Ang-(1-7). These findings demonstrate a preferential processing of Ang I into Ang-(1-7) which is not dependent on the prior formation of Ang II.