Pge2 reverses avp inhibition of hco absorption in rat mtal by
activation of protein kinase c.
Good, David W.
Departments of Medicine and Physiology & Biophysics, University
of Texas Medical Branch, Galveston, Texas 77555
APStracts 3:0031F, 1996.
In the medullary thick ascending limb (MTAL) of the rat, prostaglandin
E2 (PGE2) reverses inhibition of HCO absorption (JHCO3) by
vasopressin (AVP) by inhibiting AVP-stimulated cyclic AMP production.
To determine whether this regulation by PGE2 involves protein kinase
C (PKC), MTAL were perfused in vitro with physiologic solutions
containing 25 mM HCO (pH 7.4). With 10-10 M AVP in the bath, addition
of 10-6 M PGE2 to the bath increased JHCO3 from 7.8 +/- 0.4 to 13.0
+/- 1.1 pmol/min/mm (P < 0.01). This effect was blocked
completely by pretreatment with the PKC inhibitors staurosporine or
chelerythrine chloride (10-7 M in the bath). With both AVP and PGE2
in the bath, addition of staurosporine or chelerythrine to the bath
decreased JHCO3 from 12.2 +/- 1.1 to 7.3 +/- 0.6 pmol/min/mm (P
< 0.005). Neither staurosporine nor chelerythrine affected JHCO3
under basal conditions or in the presence of AVP alone. With AVP in
the bath, addition of phorbol myristate acetate (PMA, 10-6 M) to the
bath increased JHCO3 from 5.0 +/- 0.5 to 9.1 +/- 1.0 pmol/min/mm (P
< 0.01). Similar to PGE2, PMA had no effect on JHCO3 in the
absence of AVP or in the presence of 10-6 M bath forskolin. The
effect of PMA to stimulate JHCO3 in the presence of AVP was abolished
by pretreatment with pertussis toxin (2 x 10-11 M). We conclude that:
1) PGE2 reverses AVP inhibition of HCO absorption by activation of
PKC, 2) PKC likely increases JHCO3 by inhibiting AVP-stimulated
cyclic AMP production via a Gi-dependent mechanism, 3) PKC activity
has no influence on basal HCO absorption rate.
Received 15 November 1995; accepted in final form 9 February
1996.
APS Manuscript Number F386-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 24 February 96