Protein kinase c stimulates the small-conductance k+ channel in the
basolateral membrane of the ccd.
Lu, Ming, and Wenhui Wang.
Department of Pharmacology, New York Medical College, Valhalla, NY
10595
APStracts 3:0142F, 1996.
We have used the patch-clamp technique to study the regulation of the
activity of the basolateral small-conductance K+ channel (SK) in the
cortical collecting duct (CCD) of the rat kidney. Addition of 50-75
nM calphostin C, an agent which specifically inhibits protein kinase
C (PKC), reduced channel activity by 90% in cell-attached patches. In
contrast, addition of 1 [mu]M phorbol 12-myristate 13-acetate (PMA),
a stimulator of PKC, led to addition of "new " K+ channel
currents in 9 patches out of 20 in the basolateral membrane of the
CCD, and the mean increase in NPo, a product of channel number (N)
and open probability (Po), was 0.90 in these 9 patches. However,
application of 1 nM exogenous PKC had no significant effect on
channel activity in inside-out patches, suggesting that the PKC
effect on the activity of the SK observed in cell-attached patches
was not a result of a membrane-delimited action, such as a direct
phosphorylation of the SK or closely associated proteins. The effect
of calphostin C on the SK can be reversed by addition of either 10
[mu]M S-nitroso-N-acetyl-penicillamine (SNAP), a donor of nitric
oxide, or 100 [mu]M 8-bromoguanosine 3':5'-cyclic monophosphate. In
addition, the inhibitory effect of calphostin C on the SK was
completely abolished by pretreatment of the cells with 1 [mu]M
okadaic acid, an inhibitor of protein phosphatase. However, 100 [mu]M
Nw-nitro-L-arginine methyl ester (L-NAME), an agent that inhibits
nitric oxide synthases (NOS), blocked the SK in cell-attached patches
in the presence of okadaic acid, suggesting that the effect of
okadaic acid on calphostin C-induced inhibition of the SK was a step
before formation of nitric oxide. We conclude that PKC is involved in
the stimulation of the SK and that the effect of PKC on the SK may be
mediated by regulation of NOS activity in the CCD of the rat kidney.
Received 14 February 1996; accepted in final form 1 August 1996.
APS Manuscript Number F51-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996