Figure 1.

Macula densa-glomerular preparation and NaCl-activated ion channel in the macula densa plasma membrane. (A Left) Schematic diagram of the macula densa–juxtaglomerular apparatus, which illustrates that the macula densa lies within the TAL and is adjacent to the mesangial/arteriolar complex. (Right) Photomicrograph of macula densa–glomerular preparation. The glomerulus was fixed to the bottom of the chamber with a holding pipette (HP). The TAL was removed by dissection, thereby allowing free access of patch pipette (PP) to the macula densa cells. (B) Single-channel recordings from a cell-attached patch on a macula densa cell. An active channel in control Ringer's bath ([NaCl] = 135 mM; Left) was inactivated after removal of NaCl from the bath (Center). Return of NaCl to the bathing solution reactivated the channel (Right). Arrowheads, the closed level of channel current. Arrows, onset of step pulses. The voltage applied to the cell (−V_p) is indicated beside each current trace. Data represent nine similar experiments.