Involvement of ATP-sensitive K+ channels in spontaneous activity of isolated lymph microvessels in rats.

Physiological roles of ATP-sensitive K+ channels for spontaneous activity in isolated rat mesenteric lymph microvessels (maximum diameter ∼80-150 μm) were investigated. The lymph microvessels were cannulated with glass micropipettes and pressurized at a perfusion pressure of 6 cmH2O. Changes in the diameter and frequency of spontaneous contractions in the lymphatics were measured with videomicroscopy. Pinacidil (K+-channel opener) inhibited the spontaneous activity. In the presence of glibenclamide (selective ATP-sensitive K+-channel blocker; 10-7 and 10-6 M) and tetraethylammonium (TEA; nonselective K+-channel blocker; 10-4 and 10-3 M), the pinacidil-induced inhibition of the spontaneous contractions in lymph microvessels was significantly reversed. Glibenclamide and TEA themselves, however, did not affect the frequency of spontaneous activity in the lymph microvessels. These results suggest that ATP-sensitive K+ channels are involved in the regulation of spontaneous activity in the smooth muscles of isolated lymph microvessels of rat mesenteries.