Effect of extracellular volume expansion on erythrocyte cation transport in cirrhotic rats.
Erythrocyte intracellular Na+ and K+, and ouabain- and bumetanide-inhibitable Na+ efflux and 86Rb uptake have been measured in control and cirrhotic rats with or without extracellular volume expansion (EVE, saline, 3% body wt., 3 h). Non-expanded, cirrhotic rats showed a lower Na+ excretion (UNaV) than controls. After EVE, control rats showed a significantly higher UNaV (90%) and urinary flow (40%), than non-expanded controls. In cirrhotics, the increases in urinary flow (10%) and UNaV (17%) were not significant. No differences in intracellular Na+ and K+ levels between control and cirrhotic rats were observed. In controls none of these values changed with volume expansion, but in cirrhotic rats intracellular Na+ was significantly higher in expanded than in non-expanded rats. No differences in 86Rb uptake between non-expanded control and cirrhotic rats were observed. In controls EVE induced a decrease of pump-mediated 86Rb influx, but in cirrhotic rats, total and pump-mediated 86Rb influxes were lower in expanded than in non-expanded animals. By contrast, EVE induced a decrease in ouabain-inhibitable 86Rb uptake. In conclusion, in spite of the limitations imposed by considering the erythrocyte as representative of the renal cells, these results do not support an alteration in the response of the ouabain-inhibitable sodium pump as responsible for the lack of natriuretic response to extracellular volume expansion in cirrhotic rats. However, modification of the cotransport system in cirrhosis could play some role in this impaired response.
Hernando
N
N
Department of Physiology and Pharmacology, Faculty of Medicine, University of Salamanca, Spain.
López-Novoa
J M
JM
D000818:Animals; D001692:Biological Transport; D002034:Bumetanide / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism*; D016623:Ion Pumps; D008106:Liver Cirrhosis, Experimental / Q000378:metabolism*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012414:Rubidium Radioisotopes / Q000493:pharmacokinetics; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism
D016623:Ion Pumps; D012414:Rubidium Radioisotopes; D002034:Bumetanide; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium