Tetrahydrobiopterin augments arginine transport in rat cardiac myocytes through modulation of CAT-2 mRNA

Idit F. Schwartz, Doron Schwartz, Yoram Wollman, Tamara Chernichowski, Miriam Blum, Yoram Levo, Adrian Iaina

Research output: Contribution to journalArticlepeer-review

Abstract

Tetrahydrobiopterin (BH4) has been shown to be required for dimerization and acquisition of nitric oxide (NO) generating capacity by nitric oxide synthase (NOS). In the present study we have investigated the hypothesis that BH4 may affect NOS activity through a novel mechanism - namely, modulating arginine transport in rat cardiac myocytes. Cardiac myocytes have been previously shown to express cationic amino acid transport proteins (y+ system) CAT-1 and CAT-2. Increasing extracellular BH4 concentrations up to 0.5 mmol/L augments arginine transport in 1 mmol/L arginine media (no BH4, 558 ± 42 fmol arginine/μg protein/min; 0.1 mmol/L BH4, 580 ± 11 fmol arginine/μg protein/min; 0.5 mmol/L BH4, 944 ± 71* fmol arginine/μg protein/min; 1.0 mmol/L BH4, 983±84* fmol arginine/μg protein/min, n = 4; *P < .05 vs no BH4). Treating the cells with lipopolysaccharide (LPS) (10 μg/mL) significantly augmented arginine transport only in the presence of BH4 (no BH4, 600 ± 33 fmol arginine/μg protein/min; 0.1 mmol/L BH4, 691 ± 29*† fmol arginine/μg protein/min; 0.5 mmol/L BH4, 1123 ± 32*† fmol arginine/μg protein/min; 1.0 mmol/L BH4, 1296 ± 42*† fmol arginine/μg protein/min, n = 4; *P < .01 vs no BH4, †P < .05 vs no LPS). The administration of biopterin, sodium nitroprusside (NO donor), 2,4-diamino-6-hydroxy-pyrimidine (inhibitor of BH4 synthesis), and sepiapterin (the precursor of de novo synthesis of BH4) to unstimulated cells had no effect on arginine uptake values. Using reverse trancriptase-polymerase chain reaction, we next studied the steady state levels for CAT-1 and CAT-2 mRNA. Incubation with BH4 significantly increased CAT-2 mRNA expression in a concentration-dependent manner in 0.1, 0.5, and 1 mmol/L BH4, respectively. Northern blotting analysis further confirmed this observation. We also found that in the presence of BH4 in these concentrations, CAT-1 mRNA expression was abolished. We suggest that BH4 augments intracellular arginine availability by modulating CAT-2 mRNA expression and suggest that its presence is required for the LPS effect on trans-membrane arginine traffic.

Original languageEnglish
Pages (from-to)356-362
Number of pages7
JournalJournal of Laboratory and Clinical Medicine
Volume137
Issue number5
DOIs
StatePublished - May 2001
Externally publishedYes

Fingerprint

Dive into the research topics of 'Tetrahydrobiopterin augments arginine transport in rat cardiac myocytes through modulation of CAT-2 mRNA'. Together they form a unique fingerprint.

Cite this