IN-VITRO STIMULATION OF RENAL TUBULAR P-AMINOHIPPURATE TRANSPORT BY DEXAMETHASONE IN RAT KIDNEYS AND IN INTACT KIDNEY TISSUE OF PATIENTS SUFFERING FROM RENAL-CELL CARCINOMA

The aim of this study was to test whether or not the accumulation of p -aminohippurate (PAH) can be increased in intact human renal cortical slices obtained from tumor-bearing kidneys of patients suffering from renal cell carcinoma (RCC). Tissue slices were incubated for 24 h in W illiams medium E containing 0.01-50 mu M dexamethasone. Thereafter sli ces were placed in PAM-containing Cross-Taggart medium and PAH uptake into kidney tissue was measured for 2 h. In both rat and human renal t issue slices, PAH uptake capacity increased significantly in a concent ration-dependent manner after 24 h of incubation in dexamethasone-cont aining medium (rat, 136%; man, 156%). The stimulatory effect was alrea dy significant after 12 h of incubation. In additional experiments it was shown that incubation in triiodothyronine (T-3)-containing medium has different effects: in man, T-3 does not influence the PAH accumula tion capacity of renal cortical slices whereas in rats PAH accumulatio n is significantly lower after 24 h of incubation with T-3 Thus stimul ation of tubular transport capacity can be performed in vitro in human renal cortical slices. Discrepancies between the effects of dexametha sone and T-3 indicate different modes of action of the two hormones at the cellular level.