Renin-angiotensin system in cultured human arterial smooth muscle cells

Angiotensin converting enzyme (ACE) inhibitors were evaluated from their effects on human arterial smooth muscle cells in culture. [3H]ramipril binding has been determined in two different cell lines exhibiting ACE(+) and ACE(-) phenotypes. Specific binding occurred only in ACE(+) cells, was saturable, and displayed a Kd of 1 nM with a beta max value of 3.5 fmol/10(6) cells. Ramipril specific binding did not significantly modulate PGI2 synthesis in ACE(+) cells. By contrast, ramipril and, to a lesser extent, captopril appeared as weak inhibitors of PGI2 synthesis in ACE(-) cells. These data indicate that human arterial SMCs may express several phenotypes of the renin-angiotensin system under culture conditions and that ACE inhibitors may exert a non-renin-angiotensin-mediated pharmacological effect on eicosanoid synthesis.