Wb. Reeves et al., CL- CHANNELS IN BASOLATERAL RENAL MEDULLARY VESICLES .9. CHANNELS FROM MOUSE MTAL CELL PATCHES AND MEDULLARY VESICLES, American journal of physiology. Renal, fluid and electrolyte physiology, 38(5), 1995, pp. 621-627
The experiments reported herein compared Cl- channels fused into bilay
ers from rabbit outer medullary vesicles with Cl- channels in excised
patches of basolateral membranes from cultured mouse medullary thick a
scending limb (MTAL) cells and evaluated whether the latter were plaus
ible candidates for the Cl- channels mediating net NaCl absorption in
microperfused mouse MTAL segments. The unique signature characteristic
s of Cl- channels incorporated into lipid bilayers from outer medullar
y vesicles include activation of open probability (P-o) by increases i
n the Cl- concentrations bathing intracellular faces; activation of P-
o by protein kinase A (PKA) + ATP, when the Cl- concentrations bathing
intracellular faces are low; and no effect of PKA + ATP on P-o with h
igh cytoplasmic-face Cl- concentrations. These same properties were ob
served in Cl- channels studied using excised patches of basolateral me
mbranes from mouse MTAL cells. Moreover, in both bilayers and in excis
ed patches, the sharpest fractional increase in Cl- channel P-o occurr
ed with cytosolic-face Cl- concentration increases to values similar t
o the antidiuretic hormone (ADH)-dependent Values of intracellular Cl-
activity in microperfused mouse MTAL segments, and these fractional P
-o increases were adequate to account quantitatively for the ADH-depen
dent increase in basolateral membrane Cl- conductance in microperfused
mouse MTAL segments. Thus the excised-patch basolateral Cl- channels
reported here are reasonable candidates for those mediating net Cl- ab
sorption in the MTAL.