Forskolin and antidiuretic hormone stimulate a Ca2+-activated K+ channel in cultured kidney cells

Single channels in the apical cell membrane of primary cultured chick kidney cells were studied using the patch clamp technique. Cell-attached recordings revealed the presence of a 107 +/- 6 pS channel that increased fractional open time upon depolarization. Experiments with inside-out excised patches indicated that the channel is K+ selective, Ca2+ activated, and inhibited by Ba2+. The addition of forskolin or antidiuretic hormone (ADH) to the bath during cell-attached recordings caused an increase in the fractional open time of the channel. The activation of a K+ channel by increases in cAMP may be one way in which K+ secretion in the kidney is stimulated by ADH in vivo.