The effect of losartan on calcium uptake by bovine aortic media in vitro

The action of losartan, an AT1-angiotensin II receptor antagonist, on Ca2+ uptake by bovine aortic media in vitro was studied. This action was compared with that of nifedipine, a Ca2+ entry blocker. Ca2+ uptake values were obtained by measuring small slices of thoracic aorta tissue incubated in Kreb's solution in the presence of 45Ca. After preparation stimulation with angiotensin II (10 microM), losartan (1 microM and 10 microM) was shown to have a weaker inhibiting effect on Ca2+ uptake than nifedipine in equal concentrations. It is known that angiotensin II contracts smooth muscle by mobilizing intracellular Ca2+. The stimulating action on Ca2+ entry might be a secondary mechanism, which was studied for the first time in tissue slices derived from the aorta media. Results seem to be reasonable, since nifedipine also inhibited the spontaneous entrance of Ca2+, while losartan's action was focused only on the effects of angiotensin II.