Enhanced relaxation of porcine coronary arteries after acute exposure to a physiological level of 17β-estradiol involves non-genomic mechanisms and the cyclic AMP cascade

Abstract

1. The present study extends our previous finding that the endothelium-independent relaxation in porcine coronary artery rings is enhanced after short-term (20 min) exposure to a physiological concentration (1 nM) of 17β-estradiol and demonstrates that this effect may be attributable to activation of the cyclic AMP pathway. 2. Isometric tension was recorded in isolated rings of porcine coronary arteries. 3. Relaxation by levcromakalim and sodium nitroprusside, but not bradykinin and calcium ionophore A23187, were significantly potentiated following 20 min treatment with 1 mM 17β-estradiol. This enhancing effect was insensitive to the transcriptional and translational inhibitors, actinomycin D and cycloheximide respectively and absent following repeated washing of the rings prior to construction of relaxation-response curves. 4. The potentiating actions of 1 nM 17β-estradiol on endothelium-independent relaxation were mimicked by the cyclic AMP analogue 8-Bromo-cyclic AMP and the protein kinase A activator Sp-cyclic AMPS but not by the cyclic GMP analogue 8-Bromo-cyclic GMP. The modulatory effect of 17β-estradiol was increased in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. 5. The cyclic AMP-dependent protein kinase A inhibitor Rp-cyclic AMPS, but not the cyclic GMP antagonist Rp-8-Bromo-cyclic GMPS, effectively inhibited the enhancing effects 1 M 17β-estradiol had on the relaxation responses of levcromakalim and sodium nitroprusside. 6. These data support our earlier findings that physiologically relevant concentrations of 17β-estradiol can acutely modify vasorelaxation in vitro. Furthermore, we report that this short-term effect of 17β-estradiol on vasorelaxation appears to be mediated via non-genomic pathways and involves the cyclic AMP cascade.