Stretch may enhance the release of endothelium-derived relaxing factor in rabbit aorta

The effect of vascular stretch on the release of EDRF was studied by measuring tissue cGMP levels of rabbit. Aortic rings of rabbit were quick-frozen in liquid nitrogen during varying resting tensions, and cGMP contents were determined by radio-immunoassay. The tissue cGMP levels significantly elevated with the increase in resting tension in endothelium-intact rings, but not in endothelium-denuded rings. Deprivation of extracellular calcium abolished the stretch-induced elevation of tissue cGMP levels in endothelium-intact segments. These stretch-induced endothelium dependent tissue cGMP elevations were unaffected by Ca2+ channel blockers, nicardipine and diltiazem. Data suggest that vascular stretch may release EDRF via mechanism dependent on extracellular calcium, but probably not through voltage-dependent calcium channel.