DERANGEMENT OF PH HOMEOSTASIS IN THE RENAL PAPILLA - OCHRATOXIN-A INCREASES PH IN VASA-RECTA BLOOD

It is reported that ochratoxin A (OTA) impairs urinary acidification b y increasing the urinary pH and also increases the intracellular PPI i n Madin-Darby canine kidney cells. This study was designed to examine whether OTA deranges pH homeostasis in the interstitium for vasa recta l of the renal papilla. Rats were injected once with OTA (3 mu mol/kg body weight) intravenously (acute application) or with OTA (1.25 mu mo l/kg body weight/day) intraperitoneally for 6 days (subchronic applica tion). We measured the pH values in both the descending and ascending vasa recta blood (VR) in the renal papilla. Both the acute and subchro nic applications of OTA led to significant increases in pH values in b oth descending and ascending VR by 0.4-0.6 pH units, However, no signi ficant increases in pH values in renal arterial and aortic blood in OT A-treated rats were observed. We also examined the pH changes in colle cting-duct urine after OTA injection (3 mu mol/kg body weight). We fou nd a significant increase in pH values 30 min after OTA injection; thi s significant elevation of pH values was present during the whole expe riment (120 min). The results of this study suggest that OTA deranges pH homeostasis in the interstitium of the renal papilla, in addition t o the impairment of urinary acidification.