Early embryonic renal tubules of wild-type and polycystic kidney disease kidneys respond to cAMP stimulation with cystic fibrosis transmembrane conductance regulator/Na(+),K(+),2Cl(-) Co-transporter-dependent cystic dilation.
Metanephric organ culture has been used to determine whether embryonic kidney tubules can be stimulated by cAMP to form cysts. Under basal culture conditions, wild-type kidneys from embryonic day 13.5 to 15.5 mice grow in size and continue ureteric bud branching and tubule formation over a 4- to 5-d period. Treatment of these kidneys with 8-Br-cAMP or the cAMP agonist forskolin induced the formation of dilated tubules within 1 h, which enlarged over several days and resulted in dramatically expanded cyst-like structures of proximal tubule and collecting duct origin. Tubule dilation was reversible upon withdrawal of 8-Br-cAMP and was inhibited by the cAMP-dependent protein kinase inhibitor H89 and the cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor CFTR(inh)172. For further testing of the role of CFTR, metanephric cultures were prepared from mice with a targeted mutation of the Cftr gene. In contrast to kidneys from wild-type mice, those from Cftr -/- mice showed no evidence of tubular dilation in response to 8-Br-cAMP, indicating that CFTR Cl(-) channels are functional in embryonic kidneys and are required for cAMP-driven tubule expansion. A requirement for transepithelial Cl(-) transport was demonstrated by inhibiting the basolateral Na(+),K(+),2Cl(-) co-transporter with bumetanide, which effectively blocked all cAMP-stimulated tubular dilation. For determination of whether cystic dilation occurs to a greater extent in PKD kidneys in response to cAMP, Pkd1(m1Bei) -/- embryonic kidneys were treated with 8-Br-cAMP and were found to form rapidly CFTR- and Na(+),K(+),2Cl(-) co-transporter-dependent cysts that were three- to six-fold larger than those of wild-type kidneys. These results suggest that cAMP can stimulate fluid secretion early in renal tubule development during the time when renal cysts first appear in PKD kidneys and that PKD-deficient renal tubules are predisposed to abnormally increased cyst expansion in response to elevated levels of cAMP.
Magenheimer
Brenda S
BS
Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
St John
Patricia L
PL
Isom
Kathryn S
KS
Abrahamson
Dale R
DR
De Lisle
Robert C
RC
Wallace
Darren P
DP
Maser
Robin L
RL
Grantham
Jared J
JJ
Calvet
James P
JP
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007684:Kidney Tubules / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009924:Organ Culture Techniques; D007690:Polycystic Kidney Diseases / Q000196:embryology* / Q000235:genetics / Q000503:physiopathology; D016891:Polycystic Kidney, Autosomal Dominant / Q000209:etiology / Q000235:genetics / Q000503:physiopathology; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters / Q000502:physiology; D050396:TRPP Cation Channels; D053778:Thiazolidines / Q000494:pharmacology
D015124:8-Bromo Cyclic Adenosine Monophosphate; D000577:Amides; D001565:Benzoates; D005576:Colforsin; D000242:Cyclic AMP; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D050396:TRPP Cation Channels; D053778:Thiazolidines; C482900:3-((3-trifluoromethyl)phenyl)-5-((3-carboxyphenyl)methylene)-2-thioxo-4-thiazolidinone; C002574:dopastin