Vasopressin stimulates translocation of protein kinase C in the toad urinary bladder.
Incubation of the toad bladder epithelia with 100 nM 12-O-tetradecanoylphorbol 13-acetate (TPA) for 1, 3 and 5 min decreased cytosolic protein kinase C (PKC) activity to 85, 80 and 75% of control, while membrane-associated PKC activity increased to 127, 140 and 126% of control, respectively. Long-term treatment of epithelial cells with TPA caused downregulation of PKC with a loss of 80% of the enzymic activity. Incubation with vasopressin (AVP) for 2 min decreased cytosolic PKC activity by 20%, whereas the activity in the membrane fraction increased by 33%. PKC translocation did not occur when epithelia were stimulated with [deamino1-D-arginine8]-vasopressin which binds more specifically to the V2 receptor. Staurosporine inhibited PKC activity as well as the effect of AVP on translocation. Phorbol esters decreased the response to AVP on water transport, whereas staurosporine greatly increased the hormonal response. We conclude that TPA induces an intracellular translocation and downregulation of PKC. The translocation of PKC by AVP and the inhibition of AVP-stimulated water flow by TPA suggest a significant negative feedback loop involving PKC to modulate the action of AVP.
Sulimovici
S
S
Department of Pathology, Nassau County Medical Center, East Meadow, N.Y. 11554, USA.
Olmer
A J
AJ
Carvounis
C P
CP
D000818:Animals; D001001:Anura; D001127:Arginine Vasopressin / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004848:Epithelium / Q000201:enzymology; D005260:Female; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012076:Renal Agents / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D001743:Urinary Bladder / Q000201:enzymology* / Q000648:ultrastructure
D004791:Enzyme Inhibitors; D012076:Renal Agents; D001127:Arginine Vasopressin; D011493:Protein Kinase C; D003894:Deamino Arginine Vasopressin; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate