title: Protein kinase C regulation of p-glycoprotein-mediated xenobiotic secretion in renal proximal tubule.
abstract: Fluorescence microscopy, fluorescent substrates [daunomycin and a fluorescent cyclosporin A (CSA) derivative] and digital image analysis were used to examine the role of protein kinase C (PKC) in the control of p-glycoprotein in killifish renal proximal tubules. PKC activators, phorbol ester (phorbol 12-myristate 13-acetate, PMA) and dioctylglycerol, reduced luminal drug accumulation, and protein kinase inhibitors, staurosporine and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), increased luminal accumulation; a PMA analog that does not activate PKC was without effect. PMA effects were blocked by staurosporine. The increase in luminal fluorescence caused by staurosporine was blocked by the p-glycoprotein substrate, CSA, indicating that this component of transport was indeed mediated by p-glycoprotein. Neither PMA, dioctylglycerol, nor protein kinase inhibitors altered cellular drug accumulation. Finally, in primary cultures of flounder proximal tubule cells, PMA decreased transepithelial [3H]daunomycin secretion. This pharmacological approach demonstrates that in teleost renal proximal tubule, p-glycoprotein-mediated xenobiotic secretion is negatively correlated with changes in PKC activity, a finding that conflicts with results from studies using mammalian tumor cells that express p-glycoprotein.
authors.affiliation: Intracellular Regulation Section, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Miller
authors.forename: C R
authors.initials: CR
authors.lastname: Sussman
authors.forename: J L
authors.initials: JL
authors.lastname: Renfro
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D005399:Fishes; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D011493:Protein Kinase C / Q000378:metabolism*; D015262:Xenobiotics / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D015262:Xenobiotics; D011493:Protein Kinase C