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Photic regulation of l ‐arginine uptake in the golden hamster retina
Author(s) -
Sáenz Daniel A.,
Cymeryng Cora B.,
De Nichilo Analía,
Sacca Geraldine B.,
Keller Sarmiento María I.,
Rosenstein Ruth E.
Publication year - 2002
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.0022-3042.2001.00723.x
Subject(s) - arginine , nitric oxide , hamster , biochemistry , ornithine , biology , darkness , nitric oxide synthase , endocrinology , medicine , chemistry , amino acid , botany
One of the limiting steps in the regulation of nitric oxide (NO) synthesis is the availability of its precursor, l ‐arginine, which depends on the presence of a specific uptake system. A characterization of the l ‐arginine uptake mechanism in the golden hamster retina was performed. This mechanism was stereospecific, saturable, and monophasic, with an apparent K m of 56.1 ± 2.0 µ m and a maximum velocity of 36.0 ± 2.8 pmol/mg prot/min. The basic amino acids l ‐lysine and l ‐ornithine but not d ‐arginine or the nitric oxide synthase inhibitors, N ω ‐nitro‐ l ‐arginine methyl ester and N ω ‐nitro‐ l ‐arginine impaired l ‐arginine influx. Preincubation with l ‐lysine for 1 h prior to the transport assay significantly stimulated l ‐arginine uptake. Saturation studies of l ‐arginine uptake performed at 12.00 and 24.00 h indicated a higher value of V max at midnight than at midday. When the hamsters were placed under constant darkness or constant light for 48 h and killed at equivalent time points, representing subjective day and subjective night, the differences in l ‐arginine influx disappeared. Semiquantitative RT‐PCR analysis showed that the levels of mRNAs for both CAT‐1 and CAT‐2B were significantly higher at midnight than at midday. l ‐Arginine significantly increased cGMP accumulation in a time‐dependent manner, with maximal effects during the night. Based on these results, it might be presumed that hamster retinal l ‐arginine uptake is regulated by the photic stimulus.