Abstract
Digoxin secretory transport across renal tubular cell monolayers (LLC-PK1) grown on permeable filters was characterized. Metabolic inhibitors reduced total and specific basolateral to apical (B-A) flux of digoxin and conversely increased the apical to basolateral (A-B) flux. The specific transport of digoxin from the basolateral to the apical compartment was saturable, with a maximum velocity of transport of 184.5 ± 38.0 pmol · cm-2 · h-1 and a Michaelis-Menten constant (K(m)) of 14.1 ± 1.6 μM. In addition, B-A flux of digoxin resulted in accumulation of digoxin in the apical compartment against the concentration gradient. P-Glycoprotein inhibitors such as quinidine, verapamil, vincristine, and cyclosporine increased the net A-B flux and inhibited the total B-A flux without affecting the nonspecific flux significantly. Tetraethylammonium, a prototype substrate for an organic cation transport system, had no such effect. Our results suggest that digoxin undergoes transepithelial secretion by an energy-dependent, carrier-mediated process in renal tubules, a process that seems to be distinct from the tetraethylammonium transport system.
| Original language | English |
|---|---|
| Pages (from-to) | 40-47 |
| Number of pages | 8 |
| Journal | Canadian Journal of Physiology and Pharmacology |
| Volume | 71 |
| Issue number | 1 |
| DOIs | |
| State | Published - 1993 |
| Externally published | Yes |
Keywords
- P-glycoprotein
- cyclosporin e
- quinidine
- renal tubular secretion of digoxin
- tetraethylammonium
- verapamil
- vincristine