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, Universit[umlaut]a Paris VI, Institut Biom[umlaut]adical des
Cordeliers,15 rue de l'[umlaut]acole de m[umlaut]adecine, 75270 Paris
C[umlaut]adex 06. France.
APStracts 2:0060C, 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 C358-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 27 February 1995.