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Nitric Oxide Linked to Carvedilol's Effect on Pressure

Blockade of nitric oxide synthase prevents carvedilol from lowering blood pressure in rat study

TUESDAY, April 18 (HealthDay News) -- Carvedilol's ability to lower blood pressure may rely on a corresponding rise in nitric oxide levels, according to the results of a study in rats published in the April issue of the American Journal of Hypertension.

Ricardo A. Afonso, of the Universidade Nova de Lisboa in Portugal, and colleagues anesthetized 22 male nine-week-old Wistar rats, and monitored their mean arterial pressure and nitric oxide levels. The researchers measured the effect of intravenous carvedilol before and after treatment with L-NAME, a nitric oxide synthase (NOS) inhibitor.

Carvedilol caused the rats' arterial pressure to drop from 126.6 mm Hg to 75.9 mm Hg, and their nitric oxide level to increase from 17.9 μmol/L to 32.2 μmol/L. When the rats were treated with L-NAME, another dose of carvedilol did not lower blood pressure or raise nitric oxide.

"Our results suggest that the carvedilol-induced decrease of blood pressure is associated with an increase of plasma nitric oxide levels," the authors write. "Furthermore, NOS inhibition results in impairment of carvedilol hemodynamic effects and plasma nitric oxide levels."

The study was funded by Roche Pharmaceutical.

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