P-glycoprotein phosphorylation/dephosphorylation and cellular accumulation of L-DOPA in LLC-GA5 Col300 cells

• Type: Article in International Scientific Journal
• Date: 1999

Authors

Benedita Sampaio-Maia (Author) FMDUP; Raquel Gomes (Author) Other; Soares-da-Silva P (Author) FMDUP

Journal

Title: Journal of Autonomic Pharmacology

Vol. 19 No. 3

Pages: 173-179

ISSN: 0144-1795

Publisher: Blackwell

Indexing

ISI Web of Knowledge - 4 Citations

ISI Web of Science

Scopus - 4 Citations

Pubmed / Medline

Scientific classification

FOS: Medical and Health sciences > Other medical sciences

CORDIS: Health sciences

Other information

Authenticus ID: P-001-46Z

Abstract (EN): 1. The present work was aimed to study the effect of PKC activation and protein-serine/threonine phosphatase (PP1/PP2 A) inhibition on P-glycoprotein (P-gp) mediated transport of L-DOPA in LLC-GA5 Col300 cells, a renal cell line expressing the human P-glycoprotein in the apical membrane. 2. L-DOPA accumulation was a time-and concentration-dependent process with the following kinetic characteristics: kin, 57.3 +/- 1.2 pmol mg protein(-1) min(-1); k(out), 3.3 +/- 0.1 pmol mg(-1) protein min(-1); Amax, 10.6 +/- 0.8; Kn, 198 +/- 64 microM; Vmax, 5.2 +/- 0.7 nmol mg protein(-1). 3. Verapamil (25 microM), a P-glycoprotein inhibitor, markedly increased (approximately 40% increase) the accumulation of a non-saturating concentration of L-DOPA (2.5 microM) at both initial rate of uptake (IRU, 6 min incubation) and at steady-state (SS, 30 min incubation). 4. PKC activation with phorbol 12,13-dibutyrate (PDBu, 1, 3 and 10 nM) produced a concentration-dependent decrease in L-DOPA accumulation at SS, but not at IRU. The inactive phorbol ester, 4alpha-phorbol 12,13-didecanoate (100 nM), produced no change in L-DOPA accumulation. The effect of PDBu was completely reverted by staurosporine (100 nM). The phosphatase inhibitor okadaic acid (100 nM) reduced by 20% the accumulation of L-DOPA at IRU, but not at SS. 5. It is suggested that P-glycoprotein plays a role in regulation of intracellular availability of L-DOPA in renal epithelial cells, and phosphorylation/dephosphorylation of P-glycoprotein may be involved in the regulation of the transporter.

Language: English

Type (Professor's evaluation): Scientific