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  • Key words Renal tubular transport  (2)
  • Stimulation  (2)
  • 1
    ISSN: 1434-0879
    Keywords: Key words Renal tubular transport ; p-Aminohippurate ; Stimulation ; Renal cell carcinoma ; Dexamethasone ; Triiodothyronine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This paper is the third of a long-term planned series of papers dealing with ex vivo investigations of drug transport in human kidney. The aims of this study are (a) to investigate whether or not human renal cell carcinoma (RCC) can actively accumulate p-aminohippurate (PAH) and (b) to test the response of RCC on dexamethasone or triiodothyronine (T3) using tissue slices ex vivo. By this approach, the accumulation capacity of RCC should be stimulated as a prerequisite for an increased uptake of anti-tumour drugs. Tissue slices of RCC samples of 30 patients were incubated for 24 h in Williams medium E containing 0.01–50 μM dexamethasone or T3. Thereafter, slices were placed in PAH-containing Cross–Taggart medium, and PAH uptake into kidney tissue was measured for 2h under standardised conditions as described previously. In intact human renal cortical slices, PAH uptake capacity, expressed as slice to medium ratio (Q S/M), was about 2.8 ± 0.16 after 24 h of incubation and increased significantly in dexamethasone-containing medium in a concentration-dependent manner, up to ∼150%, whereas T3 did not influence PAH accumulation. On the other hand, in RCC the PAH accumulation capacity was completely abolished (Q S/M∼1). However, after administration of dexamethasone, the accumulated amount of PAH increased significantly in RCC tissue in a concentration-dependent manner, up to ∼190%. T3 was without effect in RCC, too. Surprisingly, the dexamethasone-mediated stimulation could be differentiated into responders and non-responders, with maximal effects at different concentrations for each patient. Nevertheless, the maximal transport rates remained low in RCC, even under hormone influence. In conclusion, a moderate stimulation of tubular transport capacity can be shown ex vivo in human RCC. This phenomenon is only of a relatively low degree compared with intact renal tissue. However, in principle, the response of RCC on dexamethasone could form a basis for further therapeutic strategies to overcome multi-drug resistance in RCC patients. For this purpose, additional experiments analysing the expression of transporters of the ABC cassette-type are in progress.
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  • 2
    ISSN: 1434-0879
    Keywords: Key words Renal tubular transport ; p-aminohippurate ; Stimulation ; Renal cell carcinoma ; Dexamethasone ; Triiodothyronine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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 Williams medium E containing 0.01–50 μM dexamethasone. Thereafter slices were placed in PAH-containing Cross-Taggart medium and PAH uptake into kidney tissue was measured for 2 h. In both rat and human renal tissue slices, PAH uptake capacity increased significantly in a concentration-dependent manner after 24 h of incubation in dexamethasone-containing medium (rat, 136%; man, 156%). The stimulatory effect was already significant after 12 h of incubation. In additional experiments it was shown that incubation in triiodothyronine (T3)-containing medium has different effects: in man, T3 does not influence the PAH accumulation capacity of renal cortical slices whereas in rats PAH accumulation is significantly lower after 24 h of incubation with T3. Thus stimulation of tubular transport capacity can be performed in vitro in human renal cortical slices. Discrepancies between the effects of dexamethasone and T3 indicate different modes of action of the two hormones at the cellular level.
    Type of Medium: Electronic Resource
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