Comparison of felodipine and nitroglycerin actions on vasomotion physiology

Felodipine is a Calcium blocker and nitroglycerin, a nitrate vasodilating agent, were compared. Two parameters were studied in vitro on bovine aortic media. Calcium uptake and vascular tone. The Calcium uptake measurement was performed by incubating in Krebs solution small slices of the preparation in the presence of 45Ca. Studies on vascular tone were performed on deendothelialized bovine aortic rings suspended in Krebs solution. Felodipine (1nM-100microM) decreases Ca2+ uptake and relaxes the preparation while nitroglycerin's 1nM-100microM) action is also inhibiting but very weak. When the preparation is stimulated by alpha 1-adrenergic against phenylephrine 1microM, then nitroglycerin 100microM has a much stronger inhibiting effect on Call uptake and vascular tone than felodipine 100microM. These results are reversed when the preparation is stimulated by KC165.4mM. Then felodipine 100nM exerts a strong inhibiting effect on Ca2+ uptake and vascular tone while nitroglycerin's 100nM inhibiting action is very weak. It is well known that in cases of endothelium disfunction the adrenergic stimulation provokes vasoconstriction and ischemia. This ischemia induces a second phase of vasoconstriction that is due to a depolarization provoked by the increased levels of extracellular K+. Felodipine is able to antagonize the consequences of such a depolarization. Thus, felodipine may be useful as an additional agent to nitroglycerin's treatment and that is the clinical message of our findings.