engleski

Hyperbaric environment downregulates renal CD77 expression in rat

During mixed gas saturation diving daily urine flow increases by about 500 ml/day, with no changes in fluid intake and glomerular filtration rate. The threshold pressure for hyperbaric diuresis appears to be from 3-7 absolute atmospheres (ATA). The excretion of Na+ is increased in the face of enhanced aldosterone secretion indicating that the Na+ transport in the proximal tubule is markedly inhibited by unknown mechanism. Na+/K+-ATPase is located in caveolae, the specific forms of lipid rafts that contain the marker proteins caveolins. Lipid rafts are the plasma membrane microdomains that are rich in cholesterol and sphingolipids. Caveolae of renal endothelial plasma membranes are particularly rich in neutral glycosphingolipid globotriaosylceramide, Gb3 or CD77. CD77 is cell receptor for Shiga toxin from Escherichia coli. Hyperbaric oxygen treatment has a beneficial effect on renal dysfunction in sepsis induced by Escherichia coli. In adult healthy kidneys, antibodies against progenitor cells marker, CD34, labelled almost all endothelial cells. The aim of this study was to determine renal CD77 and CD34 expression following exposure to hyperbaric pressure. Rats (n=11) were exposed to air pressure of 7, 5 atm (65 m of depth) for 30 min followed by decompression stops (total time of hyperbaric treatment was 150 min). CD77 and CD34 expression on suspended renal cells of hyperbaric treated rats were determined by flow cytometry and compared to untreated rats (n=12). Hyperbaric treatment significantly decreased CD34+CD77+ (from 5.93.5 to 2.92.3) as well as total CD77 positive renal cells (from 9.85.2 to 5.44.9). Total CD34 positive renal cells were not affected. Considering the colocalization of CD77 with Na+/K+-ATPase in caveolae, our results indicate at possible involvement of CD77 in mechanisms responsible for development of hyperbaric diuresis. In addition, beneficial effects of hyperbaric oxygen treatment on renal dysfunction in sepsis induced by Escherichia coli could also me modulated by CD77 decrease.

hyperbaric; kidney; CD77

nije evidentirano