Characterization of the Cl- conductance in the granular duct cells of mouse mandibular glands.
We have previously shown that mouse mandibular granular ducts contain a hyperpolarization-activated Cl- conductance. We now show that the instantaneous current/voltage (I/V) relation of this Cl- conductance is inwardly rectifying with a slope conductance of 15.4 +/- 1.8 nS (n = 4) at negative potentials and of 6.7 +/- 0.9 nS (n = 4) at positive potentials. Thus, the inward rectification seen in the steady-state I/V relation is due, not only to voltage activation of the Cl- conductance, but also to the intrinsic conductance properties of the channel. We show further that the ductal Cl- conductance is not activated by including ATP (10 mmol/l) in the pipette solution. Finally, we show that the conductance is not blocked by the addition of any of the following compounds to the extracellular solution: anthracene-9-carboxylate (A9C, 1 mmol/l), diphenylamine-2-carboxylate (DPC, 1 mmol/l), 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB, 100 mumol/l), 4,4'-diisothiocyanato-stilbene-2,2'-disulphonate (DIDS, 100 mumol/l), indanyloxyacetic acid (IAA-94, 100 mumol/l), verapamil (100 mumol/l), glibenclamide (100 mumol/l) and Ba2+ (5 mmol/l). The properties of the ductal Cl- conductance most nearly resemble those of the ClC-2 channel. Both channel types have instantaneous I/V relations that are slightly inwardly rectifying, are activated by hyperpolarization with a time-course in the order of hundreds of milliseconds, have a selectivity sequence of Br- > Cl- > I-, and are insensitive to DIDS. The only identified difference between the two is that the ClC-2 channel is 50% blocked both by DPC and A9C (1 mmol/l), whereas the ductal Cl- conductance is insensitive to these compounds.
Department of Physiology, University of Sydney, NSW, Australia.
P
P
Komwatana
A
A
Dinudom
J A
JA
Young
D I
DI
Cook
D000818:Animals; D018118:Chloride Channels / Q000502:physiology*; D004553:Electric Conductivity; D006016:Glycolates / Q000494:pharmacology; D051379:Mice; D009579:Nitrobenzoates / Q000494:pharmacology; D012469:Salivary Glands / Q000502:physiology*; D062367:ortho-Aminobenzoates / Q000494:pharmacology
D018118:Chloride Channels; D006016:Glycolates; D009579:Nitrobenzoates; D062367:ortho-Aminobenzoates; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; C015765:MK 473; C001209:fenamic acid