PGE2 reverses AVP inhibition of HCO3- absorption in rat MTAL by activation of protein kinase C

• Published in: American journal of physiology. Renal physiology Vol. 270; no. 6 Pt 2; pp. F978 - F985
• Main Author: Good, D W
• Format: Journal Article
• Language: English
• Published: United States 01.06.1996
• Subjects: Absorption - drug effects; Animals; Arginine Vasopressin - pharmacology; Bicarbonates - pharmacokinetics; Dinoprostone - antagonists & inhibitors; Dinoprostone - pharmacology; Enzyme Activation; Loop of Henle - drug effects; Loop of Henle - metabolism; Male; Pertussis Toxin; Protein Kinase C - metabolism; Rats; Rats, Sprague-Dawley; Tetradecanoylphorbol Acetate - antagonists & inhibitors; Tetradecanoylphorbol Acetate - pharmacology; Virulence Factors, Bordetella - pharmacology
• ISSN: 0002-9513; 1931-857X; 1522-1466
• DOI: 10.1152/ajprenal.1996.270.6.f978

In the medullary thick ascending limb (MTAL) of the rat, prostaglandin E2 (PGE2) reverses inhibition of HCO3- absorption (JHCO3) by arginine vasopressin (AVP) by inhibiting AVP-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) production. To determine whether this regulation by PGE2 involves protein kinase C (PKC), MTAL segments were perfused in vitro with physiological solutions containing 25 mM HCO3- (pH 7.4). With 10(-10) MAVP 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-1.mm-1 (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-1.mm-1 (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 12-myristate 13-acetate (PMA, 10(-6) M) to the bath increased JHCO3 from 5.0 +/- 0.5 to 9.1 +/- 1.0 pmol.min-1.mm-1 (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 HCO3- absorption by activation of PKC, 2) PKC likely increases JHCO3 by inhibiting AVP-stimulated cAMP production via a Gi-dependent mechanism, and 3) PKC activity has no influence on basal HCO3- absorption rate.