CELL INWARD TRANSPORT OF L-DOPA AND 3-O-METHYL-L-DOPA IN RAT RENAL TUBULES

• Type: Article in International Scientific Journal
• Date: 1994

Authors

Soares-da-Silva P (Author) Other; Fernandes MH (Author) FMDUP; Pinto-do-Ó PC (Author) Other

Journal

Title: British Journal of Pharmacology

Vol. 112

Pages: 611-615

ISSN: 0007-1188

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 66 Citations

Scopus - 65 Citations

Scientific classification

FOS: Medical and Health sciences > Other medical sciences

Other information

Authenticus ID: P-001-JZF

Abstract (EN): 1 The present study has determined the kinetics of the uptake of L-3,4-dihydroxyphenylalanine (L-DOPA) and 3-O-methyl-L-DOPA (3-OMDOPA) in rat renal tubules and examined the effect of 3-OMDOPA on the inward transport of L-DOPA and on its conversion into dopamine in kidney homogenates. 2 The accumulation of both L-DOPA and 3-OMDOPA in renal tubules was found to occur through non-saturable and saturable mechanisms. The kinetics of the saturable component of L-DOPA and 3-OMDOPA uptake in renal tubules were as follows: L-DOPA, V-max = 11.1 nmol mg(-1) protein h(-1) and K-m = 216 mu M (n = 6); 3-OMDOPA, V-max = 8.1 nmol mg(-1) protein h(-1) and K-m = 231 mu M (n = 5). The diffusion constant of the non-saturable component for the accumulation of L-DOPA and 3-OMDOPA was 0.0010 and 0.0014 mu mol(-1), respectively. 3 3-OMDOPA (100 to 2000 mu M) was found to produce a concentration-dependent decrease (29% to 81% reduction) of the saturable component of the tubular uptake of L-DOPA; the K-i value of 3-OMDOPA for inhibition of L-DOPA uptake was found to be 181 mu M (n = 5). The accumulation of L-DOPA obtained in experiments conducted at 4 degrees C was not affected by 3-OMDOPA. 4 In experiments conducted in kidney homogenates only L-DOPA (10 to 5000 mu M) was found to be decarboxylated. The V-max and K-m values for aromatic L-amino acid decarboxylase determined in the absence of 3-OMDOPA (V-max = 14.1 nmol mg(-1) protein h(-1); K-m= 62 mu M) were not significantly different from those observed when the decarboxylation of L-DOPA was carried out in the presence of 1000 mu M 3-OMDOPA (V-max = 15.7 nmol mg(-1) L protein h(-1); K-m = 68 mu M).

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 5