Connexin 30 deficiency impairs renal tubular ATP release and pressure natriuresis.
In the renal tubule, ATP is an important regulator of salt and water reabsorption, but the mechanism of ATP release is unknown. Several connexin (Cx) isoforms form mechanosensitive, ATP-permeable hemichannels. We localized Cx30 to the nonjunctional apical membrane of cells in the distal nephron and tested whether Cx30 participates in physiologically important release of ATP. We dissected, partially split open, and microperfused cortical collecting ducts from wild-type and Cx30-deficient mice in vitro. We used PC12 cells as ATP biosensors by loading them with Fluo-4/Fura Red to measure cytosolic calcium and positioning them in direct contact with the apical surface of either intercalated or principal cells. ATP biosensor responses, triggered by increased tubular flow or by bath hypotonicity, were approximately three-fold greater when positioned next to intercalated cells than next to principal cells. In addition, these responses did not occur in preparations from Cx30-deficient mice or with purinergic receptor blockade. After inducing step increases in mean arterial pressure by ligating the distal aorta followed by the mesenteric and celiac arteries, urine output increased 4.2-fold in wild-type mice compared with 2.6-fold in Cx30-deficient mice, and urinary Na(+) excretion increased 5.2-fold in wild-type mice compared with 2.8-fold in Cx30-deficient mice. Furthermore, Cx30-deficient mice developed endothelial sodium channel-dependent, salt-sensitive elevations in mean arterial pressure. Taken together, we suggest that mechanosensitive Cx30 hemichannels have an integral role in pressure natriuresis by releasing ATP into the tubular fluid, which inhibits salt and water reabsorption.
Sipos
Arnold
A
Department of Physiology and Biophysics and Department of Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA.
Vargas
Sarah L
SL
Toma
Ildikó
I
Hanner
Fiona
F
Willecke
Klaus
K
Peti-Peterdi
János
J
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000075302:Connexin 30; D017630:Connexins / Q000378:metabolism*; D053503:Epithelial Sodium Channels / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009318:Natriuresis; D011312:Pressure; D011983:Receptors, Purinergic / Q000378:metabolism
D000075302:Connexin 30; D017630:Connexins; D053503:Epithelial Sodium Channels; C100629:Gjb6 protein, mouse; D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate