Effect of tumour angiogenesis factors on the membrane of capillary and aortic endothelial cells: an e.s.r. spin-label study.

Two distinct factors have been separated from an angiogenic extract of a rat Walker 256 carcinoma, one inducing proliferation and the other migration of capillary endothelial cells in vitro, but having no detectable effect on aortic endothelial cells. The influence of these factors on the order of plasma membranes of these cells was examined by electron spin resonance, using the lipophilic spin label 5-doxyl stearic acid. No detectable effect was observed on treating whole cells or isolated membranes with proliferation factor. In contrast, exposure of capillary endothelial cell membranes to migration factor caused a reduction of membrane order, particularly at temperatures above 30 degrees C. The migration factor had no detectable effect on membrane order of aortic endothelial cells.