K+ channels serve as a negative feedback in the development of arterial myogenic tone. In this study we investigated the role of K+ channels in veins and their dependency on intraluminal pressure (IP) Saphenous veins from rats, maintained in control or in head-up tilt position for two weeks, and from humans, subjected to coronary bypass surgery, were examined The cylindrical vein segments were cannulated, and their diameter was measured by videomicroscopy (rat) or a strain-gauge transducer (human). The IP of the vessel segments was set at different levels (2-30 mmHg). We found significant myogenic tone in both rat and human saphenous veins (Ca2+-free PSS dilalcd the veins by 12.8±2.3 and 17.3±5.2 %, respectively) Tetraethylammonium (TEA), an aspecific K+ channel blocker, had no effect in rat saphenous vein, even after pressure load induced by tilt However, in human saphenous vein TEA (10 mM) caused venoconstriction (at 20 mmHg IP: from 2.5±0.3 to 2.0±0.2 mm) Selective blockers of the Ca2+-dependent (KCa) and voltage-sensitive (KV) K. channels (iberiotoxin 12 nM and 4-amino-pyridine 5 mM) decreased the diameter by 9.0±5.4 and 19.5±4.7 %, respectively, while glibenclamide (200 nM) and Ba2+ (50 μM), blockers of ATP-sensitive and inward rectifier K+ channels had no effect. We conclude that (1) in human saphenous veins Kca and KV channels play a significant role in the counterregulation of myogenic tone. (2) this mechanism is pressure-dependent, and (3) the development of the regulatory effect of K+ channel function on venous myogenic tone is a long-term process.
|Publication status||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology