Protein kinase c isoforms in rat kidney proximal tubule : acute effect of
angiotensin ii.
Karim, Z., N. Defontaine, M. Paillard, and J. Poggioli.
INSERM U356, Universite, Paris VI, Institut Biomedical des Cordeliers,15
rue de l'ecole de medecine, 75270 Paris Cedex 06. France.
APStracts 2:0062C, 1995.
We have previously shown that Angiotensin II (AII) activates the
inositolphosphate-Ca++ pathway through AT1 receptors in the rat proximal
tubule. The present study examined the effect of phorbol esters, Ca++ and AII
on protein kinase C (PKC) isoforms. The immunoblot analysis of PKC isoforms
of particulate and cytosolic fractions of proximal tubules in the absence of
stimulation revealed immunoreactive proteins when antibodies against PKC a,
d, e and z but not b, g were used. PKC a immunoreactivity was seen almost
exclusively in the soluble fraction, in contrast to PKC d, e and zwhich were
present in both soluble and particulate fractions. Phorbol dibutyrate (PDBU,
10-7M,4min ) induced the translocation of PKC a, d, e, while the inactive
phorbol ester 4-a phorbol didecanoate had no effect. The presence of 2 M
Ca++in the homogenizing medium elicited the translocation of PKC a only. PKC
activity assessed by histone phosphorylation was 0.94 0.19 and 0.67 0.09
pmol/mgP/2min in the soluble and particulate fractions . PDBU and Ionomycin
(10-6M, 4min ) increased particulate PKC specific activity to 1.56
0.18pmol/mgP/2min and 0.96 0.04pmol/mgP/2min, respectively. AII (10-7M)
induced a time-dependent increase in particulate PKC a immunoreactivity
observed after 2min and maintained during 12min. Particulate PKC e
immunoreactivity increased later, after 4min . Meanwhile PKC d and z were not
modified by AII . Accordingly, AII elicited a rise in the specific activity
of the particulate PKC which increased to 0.89 0.09pmol/mgP/2min after 2min.
This was inhibited by a 4min preincubation in the presence of 10-5M Losartan,
indicating that it was mediated through AT1 receptor activation. These data
indicate that PKC a and PKC e are potential candidates to regulate the
activity of Na+/H+ and Na+-HCO3- transporters because they are translocated
with a time course fitting with that of the reported effect of AII on those
transporters.
Received 24 June 1994; accepted in final form 6 January 1995.
APS Manuscript Number C0358-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 27 February 1995.