INDUCIBLE ENDOTHELIN MESSENGER-RNA EXPRESSION AND PEPTIDE SECRETION IN CULTURED HUMAN VASCULAR SMOOTH-MUSCLE CELLS

This study demonstrates the induction of endothelin (ET) mRNA expression and synthesis of functional ET -peptide in cultured human vascular smooth muscle cells (hVSMC). Compounds eliciting such responses in hVSMC include the vasoconstrictor hormones angiotensin II and arginine-vasopressin and the growth factors transforming growth factor ß, platelet derived growth factor AA and epidermal growth factor. Induction of ET mRNA expression in hVSMC exhibited transient kinetics (peak at 3-5 hrs. and return to basal within 7 hrs.) which differed from the more sustained ET transcript induction observed for porcine endothelial cells. ET peptide (determined by both radioimmuno-and radioreceptor assays) produced by stimulated hVSMC attained levels (∼ 120-160 pg/106 cells/4 hrs.; concentration ∼ 3 × 10-11 M) within the biologically effective concentration range of ET. Stimulated secretion of ET from hVSMC was abolished in the presence of the protein synthesis inhibitor cycloheximide. Sep-pak C18 extracts of medium from stimulated hVSMC elicited a concentration-dependent phosphoinositide catabolic response in myo-[2-3H]-inositol-prelabelled hVSMC. Our findings invoke a role for ET which extends beyond the paracrine regulation by peptide synthesized and secreted by endothelial cells. We propose that VSMC-synthesized ET may function in an autocrine manner to regulate both tone and structural modelling of vasculature. © 1990.