Endothelium-dependent vasorelaxation and the expression of calcitonin gene-related peptide in aged rats

To explore the age-related change in endothelium-dependent vasorelaxation, plasma concentrations and the expression of calcitonin gene-related peptide (CGRP) as well as serum concentrations of asymmetry dimethylarginine (ADMA), male Sprague-Dawley rats, aged 6 and 24 months were tested. The level of ADMA and CGRP in blood, and CGRP mRNA in dorsal root ganglia (DRG) were determined by high-performance liquid chromatography (HPLC), radioimmunoassay or semi-quantitative reverse-transcription polymerase chain reaction, respectively. Vasodilator responses to cumulative concentrations of acetylcholine (ACh) (3 x 10(-9) - 3 x 10(-7)M) and CGRP (3 x 10(-10) - 3 x 10(-8)M) were tested at the plateau of contraction in aortas rings. Vasodilator responses to ACh or CGRP at 24 months of age were decreased compared with 6 months. The serum concentration of ADMA at 24 months of age was significantly increased compared with 6 months, while both plasma concentrations of CGRP and the expressions of alpha- and beta-CGRP mRNA were unchanged at two age groups. The results suggest that endothelium-dependent relaxation, but not concentrations and the expressions of CGRP, is decreased in aged rats, and the decrease in endothelium dependence of vasodilator response to CGRP may be related to the elevation of endogenous ADMA.