Photic regulation of L-arginine uptake in the golden hamster retina.
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 of 56.1 +/- 2.0 microM 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(omega)-nitro-L-arginine methyl ester and N(omega)-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 Vmax 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.
Sáenz
Daniel A
DA
Laboratorio de Neuroquímica Retiniana y Oftalmología Experimental, Facultad de Medicina, Universidad de Buenos Aires, CONICET, Argentina.
Cymeryng
Cora B
CB
De Nichilo
Analia
A
Sacca
Geraldine B
GB
Keller Sarmiento
María I
MI
Rosenstein
Ruth E
RE
D000818:Animals; D001120:Arginine / Q000493:pharmacokinetics*; D027201:Cationic Amino Acid Transporter 1 / Q000235:genetics / Q000378:metabolism*; D027202:Cationic Amino Acid Transporter 2 / Q000235:genetics / Q000378:metabolism; D006224:Cricetinae; D006152:Cyclic GMP / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D008297:Male; D008647:Mesocricetus; D010775:Photic Stimulation; D017440:Photoperiod; D012333:RNA, Messenger / Q000032:analysis; D012160:Retina / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014316:Tritium
D027201:Cationic Amino Acid Transporter 1; D027202:Cationic Amino Acid Transporter 2; D012333:RNA, Messenger; D014316:Tritium; D001120:Arginine; D006152:Cyclic GMP