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  • Title: Organic anion secretion by winter flounder renal proximal tubule primary monolayer cultures.
    Author: Dawson MA, Renfro JL.
    Journal: J Pharmacol Exp Ther; 1990 Jul; 254(1):39-44. PubMed ID: 2366188.
    Abstract:
    Recent models of para-aminohippuric acid (PAH) transport by renal proximal tubule have been deduced from isolated membrane vesicles and stopped flow microperfusion. The flounder proximal tubule primary monlayer cultures mounted in Ussing chambers have provided a means to examine the relationship of these models to transepithelial transport. Unidirectional transepithelial 3H-PAH fluxes were determined in 12-day-old monolayers on floating collagen gels under continuously short-circuited conditions. The kinetic values of PAH secretory flux were complex. Over the range of 0.6 microM to 1.5 mM the K1/2 was 0.4 mM and Vmax was 80 nmol/cm2/h. Reabsorptive flux did not saturate. 1 mM probenecid inhibited 95% of the secretory flux (0.07 +/- 0.18 compared with control of 1.38 +/- 0.34 nmol/cm2/h at 10 microM PAH) and had no significant effect on reabsorptive flux (probenecid, 0.07 +/- 0.04; control, 0.05 +/- 0.01 nmol/cm2/h). 0.1 mM 4-acetamido-4'-isothiocyanalostilbene-2,2'-diasulfonic acid and 1 mM benzoylpropionic acid also significantly inhibited secretory flux (95 and 78%, respectively). These inhibitors appeared to be specific in that no effects on transepithelial potential difference, resistance or phlorizin-sensitive current were seen. Removal of Na during flux measurement reduced net PAH secretion to zero, and 1 mM ouabain reduced PAH secretory flux to 10% of control within 90 min with no effect on reabsorptive (leak) flux. Clamping transepithelial voltage to +/- 10 mV had no significant effect on PAH fluxes. Addition of glutarate to flounder saline significantly inhibited PAH secretory flux starting at 0.1 mM and caused 90% inhibition at 1 mM; no stimulation of transport was noted at any glutarate concentration.
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