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 influences 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 either in the absence or presence of test substances: angiotensin II (AII), 1 microM; AII, 1 microM + platelet derived growth factor BB-chain (PDGF-BB), 1 ng mL-1; PDGF-BB, 1 ng mL-1; PDGF-BB, 30 ng mL-1. No mechanical stress was applied. Viability was assessed by myography, protein synthesis by 6-h incorporation of 35S-methionine and proliferation by both 48-h 3H-thymidine-incorporation and immunohistochemical analysis using the thymidine analogue 5-bromo-2'-deoxyuridine. After 3 days in culture, the contractile responses of arteries to phenylephrine, serotonin, AII 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 3H-thymidine incorporation of unstimulated arteries 3.4- (mesenteric) and 2.8-fold (epigastric). The other treatments affected neither protein synthesis nor proliferation. Immunohistochemical analysis showed that the proliferation was occurring primarily in the adventitia and that the levels of apoptosis were unaltered by culture. The effects of AII and PDGF-BB on remodelling did not correlate with their contractile effects: epigastric arteries responded strongly to AII and PDGF-BB, while mesenteric arteries responded weakly. The results suggest that organ culture conditions which preserve contractile function may not be sufficient to preserve trophic mechanisms.