Targeted delivery of a substrate for P-glycoprotein to renal cysts in vitro.

Bodipy-verapamil has been tested as a fluorescent substrate for P-glycoprotein-mediated transepithelial secretion in MDCK-C5A epithelia. Net transepithelial secretion (Jnet) of [3H]vinblastine from basal-to-apical surfaces of monolayer epithelia is inhibited by taxotere, verapamil and Bodipy-verapamil primarily by a reduction in basal to apical vinblastine (Jb-a) transport. Bodipy-verapamil is itself subject to transepithelial net secretion by MDCK-C5A epithelia; at 5 microM a Jnet of -310 +/- 32 nmol cm-2 h-1 (n = 3) was observed. When MDCK-C5A cells are grown to form enclosed cysts in hydrated collagen gel. Bodipy-verapamil is accumulated within the cyst lumen showing that epithelial P-glycoprotein function may be used to target substrates to renal cysts.