The present study was undertaken in order to examine transduction mechanism involved in the single application of 100 μM homocysteine (Hcy) on isolated rat femoral artery (RFA) rings equilibrated on the basal tone; to establish if a single application of 100 μM Hcy alters contractile effect of phenylephrine (Phe), or oppositely the relaxant effect of acetylcholine (ACh) or bradykinin (BK) after 60-min-long incubation of 100 μM Hcy; and finally to identify morphological changes on the vascular wall after a 24-h-long incubation of 100 μM Hcy. Hcy produced contractile response of intact RFA, which was increased after endothelial denudation, while decreased by urapidil (an α1 receptor blocker), nifedipine (a voltage-gated L-type Ca++ channel blocker) or indomethacin (a cyclooxygenase inhibitor). The initial RFA contraction evoked by Phe was further increased by the single addition of Hcy, which was not the case when ouabain (an inhibitor of Na+/K+-ATPase) was preincubated. After 60-min-long incubation of Hcy relaxant actions of ACh and BK were unaltered, equieffective and equipotent. A 24-h-long incubation of RFA rings with Hcy produced an impairment of vascular endothelium, expressed as a minor or more pronounced interruption of endothelial cells.
Keywords: Ca++ channels; Na+/K+-ATPase; endothelium; femoral artery; homocysteine.