D-Alanine Is Reduced by Ocular Hypertension in the Rat Retina

ABSTRACT

Purpose: The purpose of this study was to investigate the physiological changes of amino acids in the rat retina caused by ocular hypertension.

Methods: Adult Wistar rats were used as an experimental model of ocular hypertension. Retinas were hydrolyzed with HCl at 108°C to isolate amino acids. Residual amino acids were measured by reverse-phase high-performance liquid chromatography and the total volume of residual amino acids and the ratio of D- and L-amino acids were analyzed. Free D- and L-alanine levels were also measured using two-dimensional HPLC.

Results: The amount of retinal alanine decreased in ocular hypertension compared with the control (p < .05, Student’s t-test); the amounts of other amino acids did not differ between the two conditions.

The D/L ratio of alanine was higher than that of other amino acids. Ocular hypertension reduced the D/L ratio of retinal alanine, while that of other amino acids was unchanged. Ocular hypertension increased the D/L ratio of free alanine.

Conclusions: Ocular hypertension reduced the D/L ratio of retinal alanine, presumably due in large part to alanine peptides.

Keywords:

• D-alanine
• ocular-hypertension
• rat
• retina

Acknowledgments

We are grateful to Dr. Kenji Hamase (Kyushu University.), Masao Mita, and Maiko Nakane (Shiseido Corp.) for the measurement of the D-and L-alanine concentrations. This study was collaborated with the Research Reactor Institute (Kyoto University).

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Authors’ contributions

TK was primarily responsible for experimental concept, design, and drafting of the manuscript. HS performed data acquisition and analysis. YK collected the animal samples. YI, YM, RA, KI, and YK were involved in drafting of the manuscript. All authors read and approved the final manuscript.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Supplemental material

Supplemental data for this article can be accessed here.