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Age-related involvement of the endothelium in β-adrenoceptor-mediated relaxation of rat aorta

2000; Elsevier BV; Volume: 397; Issue: 1 Linguagem: Inglês

10.1016/s0014-2999(00)00193-x

1879-0712

Andrea van der Zypp, Khong-Bee Kang, H. Majewski,

Eicosanoids and Hypertension Pharmacology

The signalling pathway involved in β-adrenoceptor relaxation was studied in aortas from rats either 8 or 54 weeks of age. The vasorelaxation produced by isoprenaline was almost completely abolished by endothelium removal in 54-week aortas, whereas in 8-week aortas, the effect was much smaller. The nitric oxide synthase inhibitor N-methyl-1-arginine acetate (l-NMMA) partially attenuated the isoprenaline induced relaxation to a similar extent in both age groups when the endothelium was intact, suggesting that although nitric oxide was involved, it could not explain the age-related difference. The K+ channel inhibitor, tetraethylammonium inhibited isoprenaline vasorelaxation to a larger degree in 54-week compared to 8-week aortas indicating that K+ channels were responsible for the age-related differences. We suggest that as the animals age, the smooth muscle cyclic AMP signalling system declines, and that this is compensated for by an alternate pathway involving the opening of K+ channels.