Abstract
Background and objectives: Beta-blockers are the most used antihypertensive agents due to their blood pressure-lowering effect alongside decreasing heart rate. Nebivolol (NB) seems to provide typical antihypertensive alongside vasorelaxant effects. The present study aimed to elucidate the differential impacts of NB on bovine coronary tone with a specific focus on the involvement of nitric oxide and K+ channels. Using an in vitro isolated bovine coronary segments, vascular reactivity was assessed through tension measurement in response to NB. Methods: Using isolated tissue baths, the impact of NB on bovine coronary artery segments' contractility was assessed. The contractions were induced by KCl, NB was added to check the vasorelaxant effects, and methylene blue was used to examine the role of NO. In addition, the effect on tone was compared with another β-blocker, propranolol, to determine the role of adrenoceptor. Results: NB significantly induced relaxation in the coronary bovine artery segments, 49.7 ± 7.84 VS 4.44 ± 6.87. Incubation with methylene blue (30 μM) inhibited NB relaxation, 46.08 ± 4.37 vs MB 12.16 ± 4.28, KCl depolarization did not affect on the relaxation induced by NB in comparison to U46619 precontraction KCl 39.52 ± 6.19 vs U46619 58.41 ± 28.92. Propranolol had no effect on the coronary tone when compared to NB, 87.05 ± 7.05 VS Propranolol 34.28 ± 5.71. Conclusions: Our results show that NO but not K+ channel activation is involved in the mechanism of NB induced coronary artery relaxation. These results highlight the necessity of taking these pathways into account when extrapolating the effects of NB in clinical settings.
