Production of angiotensin II by homogeneous cultures of vascular smooth muscle cells from spontaneously hypertensive rats

Production of angiotensin II (Ang II) in spontaneously hypertensive rats (S HR)-derived vascular smooth muscle cells (VSMC) has now been investigated. A nonpeptide antagonist (CV-11974) of Ang II type 1 receptors inhibited:bas al DNA synthesis in VSMC from SHR, but it had no effect on cells from Wista r-Kyoto (WKY) rats. Ang II-like immunoreactivity, determined by radioimmuno assay after HPLC, was readily detected in conditioned medium and extracts o f SHR-derived VSMC, whereas it was virtually undetectable in VSMC from WKY rats. Isoproterenol increased the amount of Ang II-like immunoreactivity in conditioned medium and extracts of SHR-derived VSMC, whereas the;angiotens in-converting enzyme inhibitor delapril significantly reduced the amount of Ang II-like immunoreactivity in conditioned medium and extracts of these c ells. Reverse transcription-polymerase chain reaction analysis revealed tha t the abundance of mRNAs encoding angiotensinogen, cathepsin D, and angiote nsin-converting enzyme was greater in VSMC from SHR than in cells from WKY rats. The abundance of cathepsin D protein by Western blotting was greater in VSMC from SHR than in cells from WKY rats. Ang I-generating and acid pro tease activities were detected in VSMC from SHR, but not in cells from WKY rats,These results suggest that SHR-derived VSMC generate ng II with increa ses in angiotensinogen, cathepsin D, and angiotensin-converting enzyme, whi ch contribute to the basal growth. Production of Ang II by homogeneous cult ures of VSMC is considered as a new mechanism of hypertensive vascular dise ase.