Effects of epidermal growth factor and transforming growth factor-α on rabbit proximal tubule solute transport

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Abstract

The present in vitro microperfusion study examined the direct effects of epidermal growth factor (EGF) and transforming growth factor α (TGF-α) on rabbit proximal convoluted tubule (PCT) solute transport. Tubules were perfused with an ultrafiltrate-like solution and bathed in an ultrafiltrate- like solution containing albumin. Albumin binding studies showed that both growth factors were highly protein bound with a free fraction of EGF of 0.31 ± 0.04% and TGF-α of 1.08 ± 0.15%. EGF at concentrations from 3 x 10- 11 M to 3 x 10-8 M stimulated phosphate transport (J(Phos)) in a dose- dependent fashion but did not affect volume absorption (J(v)) or bicarbonate transport (J(tCO2)). At 3 x 10-7 M, EGF stimulated PCT J(v) and J(tCO2) in addition to the stimulation in J(Phos). TGF-α stimulated J(v), J(tCO2), and J(Phos), but its effects were seen at a concentration that was 100-fold lower than that where EGF affected PCT transport. At 3 x 10-13 M, TGF-α stimulated J(tCO2), and at 3 x 10-12 M, TGF-α also stimulated J(v) and J(Phos). EGF receptor downregulation with 3 x 10-8 M EGF was able to block the effect of 3 x 10-10 M TGF-α on J(v) and J(tCO2). Neither luminal EGF nor TGF-α had an effect on PCT transport. PCT bicarbonate and mannitol permeabilities were also not affected by either growth factor. These results demonstrate that EGF and TGF-α have direct effects on PCT solute transport.

Original languageEnglish (US)
Pages (from-to)F459-F465
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Volume266
Issue number3 35-3
StatePublished - 1994

Keywords

  • bicarbonate transport
  • glucose transport
  • in vitro microperfusion
  • phosphate transport
  • volume absorption

ASJC Scopus subject areas

  • Physiology

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