Collateral vessel formation: isolation of a transferable factor promoting a vascular response

Collateral vessel formation to the kidney was induced by renal artery stenosis or embolization in six dogs. Extracts from control and collateral-forming kidneys were assessed for their ability to promote a vascular response in the hamster cheekpouch. The highly significant response evoked by particulate and soluble fractions of cytoplasm from collateral-forming kidneys suggests a humoral element in collateral vessel formation.