Uroguanylin and guanylin regulate transport of mouse cortical collecting duct independent of guanylate cyclase C.
BACKGROUND
Electrolyte and water homeostasis mostly depend on differentially regulated intestinal and renal transport. Guanylin and uroguanylin were proposed as first hormones linking intestinal with renal electrolyte and water transport, which is disturbed in pathophysiology. Guanylate cyclase C is the intestinal receptor for these peptides, but in guanylate cyclase C-deficient mice renal effects are retained. Unlike for the intestine the sites of renal actions and cellular mechanisms of guanylin peptides are still unclear.


METHODS
After first data on proximal tubular effects in this study their effects are examined in detail in mouse cortical collecting duct (CCD). Effects of guanylin peptides on principal cells of isolated mouse CCD were studied by slow whole-cell patch-clamp analysis, reverse transcription-polymerase chain reaction (RT-PCR), and microfluorimetric measurements of intracellular Ca2+.


RESULTS
Guanylin peptides depolarized or hyperpolarized principal cells. Whereas 8-Br-cyclic guanosine monophosphate (8-Br-cGMP) hyperpolarized, 8-Br-cyclic adenosine monophosphate (8-Br-cAMP) depolarized principal cells. All effects of guanylin peptides were inhibited by Ba2+. Hyperpolarizations were blocked by clotrimazole or protein kinase G (PKG) inhibition, suggesting an involvement of basolateral Ca2+- and cGMP-dependent K+ channels. Effects remained in CCD isolated from guanylate cyclase C-deficient mice. Depolarizations were inhibited by arachidonic acid or inhibition of phospholipase A2 (PLA2), but not by protein kinase A (PKA) inhibition. Conclusion. These results suggest the existence of two signaling pathways for guanylin peptides in principal cells of mouse CCD. One pathway is cGMP- and PKG-dependent but not mediated by guanylate cyclase C, the second involves PLA2 and arachidonic acid. The first pathway most likely leads to an activation of the basolateral K+-conductance while the latter probably results in decreased activity of ROMK channels in the luminal membrane.
Sindić
Aleksandra
A
Universitätsklinikum Münster, Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Münster, Germany.
Velic
Ana
A
Başoglu
Candan
C
Hirsch
Jochen R
JR
Edemir
Bayram
B
Kuhn
Michaela
M
Schlatter
Eberhard
E
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D005768:Gastrointestinal Hormones / Q000378:metabolism* / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D045265:Natriuretic Peptides / Q000378:metabolism* / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism; D054467:Phospholipases A2; D011188:Potassium / Q000378:metabolism; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D005768:Gastrointestinal Hormones; D045265:Natriuretic Peptides; D018000:Receptors, Peptide; C072685:guanylin; C084362:uroguanylin; D016718:Arachidonic Acid; D019869:Phosphatidylinositol 3-Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D006162:Guanylate Cyclase; C000613655:Gucy2c protein, mouse; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D006152:Cyclic GMP; D011188:Potassium; D002118:Calcium