Effect of mitogens on growth and contractile responses of rat small arteries: In vitro studies

Rat mesenteric and epigastric small arteries were cultured to investigate i nfluences of mitogens on contractility, proliferation and protein synthesis . Wistar rat arteries were cultured in serum-free Dulbecco's Modified Eagle Medium, first, for 24 h to equilibrate and then for a further 24-48 h eith er in the absence or presence of test substances: angiotensin II (AII), 1 m u M; AII, 1 mu M + platelet derived growth factor BB-chain (PDGF-BB), 1 ng mL(-1); PDGF-BB, 1 ng mL(-1); PDGF-EB, 30 ng mL(-1). No mechanical stress w as applied. Viability was assessed by myography, protein synthesis by 6-h i ncorporation of S-35-methionine and proliferation by both 48-h H-3-thymidin e-incorporation and immunohistochemical analysis using the thymidine analog ue 5-bromo-2'-deoxyuridine. After 3 days in culture, the contractile respon ses of arteries to phenylephrine, serotonin, Ali and PDGF-BB were preserved . Stimulation with PDGF-BB (30 ng mL(-1)) increased protein synthesis 1.5- (mesenteric) and 1.9-fold (epigastric). Similarly, stimulation with PDGF-BB (30 ng mL(-1)) increased H-3-thymidine incorporation of unstimulated arter ies 3.4- (mesenteric) and 2.8-fold (epigastric). The other treatments affec ted neither protein synthesis nor proliferation. Immunohistochemical analys is showed that the proliferation was occurring primarily in the adventitia and that the levels of apoptosis were unaltered by culture. The effects of Alt and PDGF-BB on remodelling did not correlate With their contractile eff ects: epigastric arteries responded strongly to All and PDGF-BB, while mese nteric arteries responded weakly. The results suggest,that organ culture co nditions which preserve contractile function may not be sufficient to prese rve trophic mechanisms.