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 i n isolated rat mesenteric lymph microvessels (maximum diameter similar to 8 0-150 mu m) were investigated. The lymph microvessels were cannulated with glass micropipettes and pressurized at a perfusion pressure of 6 cmH(2)O. C hanges in the diameter and frequency of spontaneous contractions in the lym phatics were measured with videomicroscopy. Pinacidil (K+-channel opener) i nhibited the spontaneous activity. In the presence of glibenclamide (select ive ATP-sensitive K+-channel blocker; 10(-7) and 10(-6) M) and tetraethylam monium (TEA; nonselective K+-channel blocker; 10(-4) and 10(-3) M), the pin acidil-induced inhibition of the spontaneous contractions in lymph microves sels was significantly reversed. Glibenclamide and TEA themselves, however, did not affect the frequency of spontaneous activity in the lymph microves sels. These results suggest that ATP-sensitive K+ channels are involved in the regulation of spontaneous activity in the smooth muscles of isolated ly mph microvessels of rat mesenteries.