Na+: K+: ATPase mRNA expression in the kidney during adaptation to sodium intake and furosemide treatment

Background. Nephron tubular epithelium possesses the capacity of adaptation to any salt ingestion condition. The mechanism of adaptation is due in par t to an increase in the activity of Na+:K+:ATPase at the basolateral membra ne. The goal. of the present study was to analyze the long-term regulation of the Na+:K+:ATPase alpha (1)-subunit mRNA expression during changes in Na Cl metabolism. Methods. Male Wistar rats given a normal, high, or low NaCl diet,and intrap eritoneal administration of the loop diuretic furosemide from 12 h to 7 day s were studied. Rats were kept in metabolic cages 4 days before and through out the study to determine daily urinary electrolyte excretion and osmolari ty. At the end of each experimental period, creatinine clearance and serum electrolytes were also measured. Total RNA was extracted from each individu al cortex or outer medulla and from pooled inner medullas using the guanidi ne/cesium chloride method. Na+:K+:ATPase alpha (1)-subunit mRNA expression was assessed by nonradioactive dot-blot analysis. Results. Experimental maneuvers were well tolerated and all groups develope d the appropriate renal response to each experimental condition. Urinary so dium excretion was significantly higher in rats administered a high sodium diet or furosemide and lower in rats treated with a low sodium diet after 7 days of treatment. Glomerular filtration rate was similar among all groups . However, the level of expression of the Na+:K+:ATPase alpha (1)-subunit d id not change in any model. Conclusions. Nephron adaptation to the modification in NaCl intake or furos emide administration over 7 days did not include changes in Na+:K+:ATPase a lpha (1)-subunit mRNA levels. (C) 2001 IMSS. Published by Elsevier Science Inc.