Inhibition of calcium-independent luminal uptake of L-dopa by calmodulin antagonists in immortalized rat capillary cerebral endothelial cells

• Type: Article in International Scientific Journal
• Date: 2001

Authors

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

Journal

Title: Cell Biology International

Vol. 25 No. 3

Pages: 245-252

ISSN: 1065-6995

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 3 Citations

ISI Web of Science

Scopus - 3 Citations

Pubmed / Medline

Scientific classification

FOS: Medical and Health sciences > Other medical sciences

CORDIS: Health sciences

Other information

Authenticus ID: P-000-WVT

Abstract (EN): The present study examined the involvement of protein kinase A (PKA), protein kinase G (PKG), protein kinase C (PKC), protein tyrosine kinase (PTK) and Ca(2+)/calmodulin mediated pathways on the luminal uptake of L-DOPA through the L-type amino acid transporter in immortalized rat capillary cerebral endothelial (REB-4) cells. Non-linear analysis of the saturation curve for L-DOPA revealed a K(m)value (in microM) of 71+/-9 and a V(max)value of 17+/-1 (in nmol mg protein/6 min). L-DOPA uptake at the luminal cell border was a sodium-independent process and insensitive to N-(methylamino)-isobutyric acid (MeAIB, 1 m m), but sensitive to 2-aminobicyclo(2,2,1)-heptane-2-carboxylic acid (BHC, IC(50)=140 microM). The Ca(2+)/calmodulin inhibitors calmidazolium and trifluoperazine inhibited L-DOPA (2.5 microM) uptake with IC(50)s of 23 and 33 microM, respectively. The inhibitory effect of BHC on the accumulation of L-DOPA was of the competitive type, whereas that of calmidazolium and trifluoperazine was of the non-competitive type. Modulators of PKA (cyclic AMP, forskolin, isobutylmethylxanthine and cholera toxin), PKG (cyclic GMP, zaprinast, LY 83583 and sodium nitroprusside), PKC (phorbol 12,13-dibutyrate, staurosporine and chelerythrine) and PTK (genistein and tyrphostin 25) failed to affect the accumulation of a non-saturating (2.5 microM) concentration of L-DOPA. It is concluded that L-DOPA uptake in RBE-4 cells is promoted through the L-type amino acid transporter and appears to be under the control of calmodulin mediated pathways.

Language: English

Type (Professor's evaluation): Scientific