Aquaporin-1 and endothelial nitric oxide synthase expression in capillary endothelia of human peritoneum

Am J Physiol. 1998 Jul;275(1):H234-42. doi: 10.1152/ajpheart.1998.275.1.H234.


Water transport during peritoneal dialysis (PD) requires ultrasmall pores in the capillary endothelium of the peritoneum and is impaired in the case of peritoneal inflammation. The water channel aquaporin (AQP)-1 has been proposed to be the ultrasmall pore in animal models. To substantiate the role of AQP-1 in the human peritoneum, we investigated the expression of AQP-1, AQP-2, and endothelial nitric oxide synthase (eNOS) in 19 peritoneal samples from normal subjects (n = 5), uremic patients treated by hemodialysis (n = 7) or PD (n = 4), and nonuremic patients (n = 3), using Western blotting and immunostaining. AQP-1 is very specifically located in capillary and venule endothelium but not in small-size arteries. In contrast, eNOS is located in all types of endothelia. Immunoblot for AQP-1 in human peritoneum reveals a 28-kDa band (unglycosylated AQP-1) and diffuse bands of 35-50 kDa (glycosylated AQP-1). Although AQP-1 expression is remarkably stable in all samples whatever their origin, eNOS (135 kDa) is upregulated in the three patients with ascites and/or peritonitis (1 PD and 2 nonuremic patients). AQP-2, regulated by vasopressin, is not expressed at the protein level in human peritoneum. This study 1) supports AQP-1 as the molecular counterpart of the ultrasmall pore in the human peritoneum and 2) demonstrates that AQP-1 and eNOS are regulated independently of each other in clinical conditions characterized by peritoneal inflammation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aquaporin 1
  • Aquaporin 2
  • Aquaporin 6
  • Aquaporins*
  • Biopsy
  • Blood Group Antigens
  • Capillaries
  • Child
  • Child, Preschool
  • Endothelium, Vascular / metabolism*
  • Female
  • Humans
  • Immunohistochemistry
  • Ion Channels / analysis
  • Ion Channels / biosynthesis*
  • Kidney Failure, Chronic / metabolism
  • Kidney Failure, Chronic / pathology
  • Kidney Failure, Chronic / therapy
  • Male
  • Middle Aged
  • Nitric Oxide Synthase / analysis
  • Nitric Oxide Synthase / biosynthesis*
  • Nitric Oxide Synthase Type III
  • Peritoneum / blood supply
  • Peritoneum / cytology
  • Peritoneum / pathology
  • Reference Values
  • Renal Dialysis
  • Uremia / metabolism
  • Uremia / pathology
  • Uremia / therapy
  • Venules


  • AQP1 protein, human
  • AQP2 protein, human
  • Aquaporin 2
  • Aquaporin 6
  • Aquaporins
  • Blood Group Antigens
  • Ion Channels
  • Aquaporin 1
  • NOS3 protein, human
  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type III