OCHRATOXIN-A DISTURBS PH HOMEOSTASIS IN THE KIDNEY - INCREASES IN PH AND HCO3(-) IN THE TUBULES AND VASA-RECTA

This study was designed to elucidate the effects of ochratoxin A (OTA) on pH homeostasis in the kidney. We measured pH in the proximal (PT) and the distal (DT) tubular fluid, the collecting duct urine (CD), the descending and the ascending vasa recta blood (VR), and the renal art erial blood (RA). OTA increased PII significantly in PT DT, CD as well as in the descending and ascending VR, whereas pH in RA remained unch anged. We further determined CO2 tension (pCO(2)) and HCO3- in PT, CD as well as in the descending and ascending VR. OTA significantly incre ased HCO3- in PT, CD and the descending and ascending VRI with no chan ges in pCO(2). Therefore, the increases in pH in PT, CD and the descen ding and ascending VR result from the increase in HCO3-. Our results s uggest that OTA inhibits HCO3- reabsorption in the tubules, leading to the impairment of urinary acidification, and that OTA further leads t o the disturbance of the acid-base state (alkalinization) in the inter stitium in renal papilla, The impairment of urinary acidification may contribute to the disturbance of pH homeostasis in the renal papilla. The disturbance of pH homeostasis by OTA could be related to its nephr otoxicity.