Atrial natriuretic peptide enhances microvascular albumin permeability by the caveolae-mediated transcellular pathway.
OBJECTIVE
Cardiac atrial natriuretic peptide (ANP) participates in the maintenance of arterial blood pressure and intravascular volume homeostasis. The hypovolaemic effects of ANP result from coordinated actions in the kidney and systemic microcirculation. Hence, ANP, via its guanylyl cyclase-A (GC-A) receptor and intracellular cyclic GMP as second messenger, stimulates endothelial albumin permeability. Ultimately, this leads to a shift of plasma fluid into interstitial pools. Here we studied the role of caveolae-mediated transendothelial albumin transport in the hyperpermeability effects of ANP.


RESULTS
Intravital microscopy studies of the mouse cremaster microcirculation showed that ANP stimulates the extravasation of fluorescent albumin from post-capillary venules and causes arteriolar vasodilatation. The hyperpermeability effect was prevented in mice with conditional, endothelial deletion of GC-A (EC GC-A KO) or with deleted caveolin-1 (cav-1), the caveolae scaffold protein. In contrast, the vasodilating effect was preserved. Concomitantly, the acute hypovolaemic action of ANP was abolished in EC GC-A KO and Cav-1(-/-) mice. In cultured microvascular rat fat pad and mouse lung endothelial cells, ANP stimulated uptake and transendothelial transport of fluorescent albumin without altering endothelial electrical resistance. The stimulatory effect on albumin uptake was prevented in GC-A- or cav-1-deficient pulmonary endothelia. Finally, preparation of caveolin-enriched lipid rafts from mouse lung and western blotting showed that GC-A and cGMP-dependent protein kinase I partly co-localize with Cav-1 in caveolae microdomains.


CONCLUSIONS
ANP enhances transendothelial caveolae-mediated albumin transport via its GC-A receptor. This ANP-mediated cross-talk between the heart and the microcirculation is critically involved in the regulation of intravascular volume.
Institute of Physiology, University of Würzburg, Germany.
Wen
W
Chen
Birgit
B
Gassner
Sebastian
S
Börner
Viacheslav O
VO
Nikolaev
Nicolas
N
Schlegel
Jens
J
Waschke
Nadine
N
Steinbronn
Ruth
R
Strasser
Michaela
M
Kuhn
D000418:Albumins / Q000378:metabolism; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology* / Q000502:physiology*; D002199:Capillary Permeability / Q000187:drug effects* / Q000502:physiology*; D021941:Caveolae / Q000187:drug effects / Q000502:physiology; D051242:Caveolin 1 / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D004705:Endocytosis / Q000187:drug effects; D042783:Endothelial Cells / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D051381:Rats; D017461:Receptors, Atrial Natriuretic Factor / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D057900:Transcytosis / Q000187:drug effects
D000418:Albumins; D051242:Caveolin 1; D009320:Atrial Natriuretic Factor; D017461:Receptors, Atrial Natriuretic Factor; C091715:atrial natriuretic factor receptor A