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 × 10-11 M to 3 × 10-8 M stimulated phosphate transport (JPhos) in a dose-dependent fashion but did not affect volume absorption (Jv) or bicarbonate transport (JtCO2). At 3 × 10-7 M, EGF stimulated PCT Jv and JtCO2 in addition to the stimulation in JPhos. TGF-α stimulated Jv, JtCO2, and JPhos, but its effects were seen at a concentration that was 100-fold lower than that where EGF affected PCT transport. At 3 × 10-13 M, TGF-α stimulated JtCO2, and at 3 × 10-12 M, TGF-α also stimulated Jv and JPhos. EGF receptor downregulation with 3 × 10-8 M EGF was able to block the effect of 3 × 10-10 M TGF-α on Jv and JtCO2. 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 language | English (US) |
|---|---|
| Pages (from-to) | F459-F465 |
| Journal | American Journal of Physiology - Renal Fluid and Electrolyte Physiology |
| Volume | 266 |
| Issue number | 3 35-3 |
| State | Published - Mar 1994 |
Keywords
- Bicarbonate transport
- Glucose transport
- In vitro microperfusion
- Phosphate transport
- Volume absorption
ASJC Scopus subject areas
- Physiology