Affordable Access

Regulation of UT-A1-mediated transepithelial urea flux in MDCK cells.

Published Article
American journal of physiology. Cell physiology
Publication Date
PMID: 16641165


Transepithelial [(14)C]urea fluxes were measured across cultured Madin-Darby canine kidney (MDCK) cells permanently transfected to express the urea transport protein UT-A1. The urea fluxes were typically increased from a basal rate of 2 to 10 and 25 in the presence of vasopressin and forskolin, respectively. Flux activation consisted of a rapid-onset component of small amplitude that leveled off within approximately 10 min and at times even decreased again, followed by a delayed, strong increase over the next 30-40 min. Forskolin activated urea transport through activation of adenylyl cyclase; dideoxyforskolin was inactive. Vasopressin activated urea transport only from the basolateral side and was blocked by OPC-31260, indicating that its action was mediated by basolateral V(2) receptors. In the presence of the phosphodiesterase inhibitor IBMX, vasopressin activated as strongly as forskolin. By itself, IBMX caused a slow increase over 50 min to approximately 5 8-Bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP; 300 microM) activated urea flux only when added basolaterally. IBMX augmented the activation by basolateral 8-BrcAMP. Urea flux activation by vasopressin and forskolin were only partially blocked by the protein kinase A inhibitor H-89. Even at concentrations >10 microM, urea flux after 60 min of stimulation was reduced by <50%. The rapid-onset component appeared unaffected by the presence of H-89. These data suggest that activation of transepithelial urea transport across MDCK-UT-A1 cells by forskolin and vasopressin involves cAMP as a second messenger and that it is mediated by one or more signaling pathways separate from and in addition to protein kinase A.

There are no comments yet on this publication. Be the first to share your thoughts.


Seen <100 times