Ascorbate in the rat lens: dependence on dietary intake.
OBJECTIVE
To establish a method for sample preparation to measure ascorbate in whole lenses and to investigate whether lens ascorbate concentration is dependent on dietary ascorbate intake.


METHODS
Four groups of 3 young Sprague-Dawley rats each were fed chow containing L-ascorbate, either 0.0, 5.7, 57.0 or 114.0 mmol/kg for a duration of 4 weeks. Thereafter, each rat was sacrificed. The lens was extracted, photographed, and lens wet weight was measured. The lens was homogenized in 1.0 ml of 0.25% metaphosphoric acid, the homogenate was centrifuged and the supernatant ultrafiltered. The filtrate was injected into an ion exchange, reversed-phase Polypore H HPLC column equipped with a 254-nm ultraviolet detector. Samples were calibrated against an L-ascorbate standard. Polynomial regression analysis was performed on the data.


RESULTS
All lenses were devoid of cataract. A 95% confidence interval for baseline content of ascorbate without any dietary intake was estimated to be 0.16+/-0.01 micromol/g wet weight of lens. The lens ascorbate concentration increased linearly with dietary ascorbate intake with an increased rate, estimated as a 95% confidence interval of 0.33+/-0.18 (micromol ascorbate) (g lens)-1)(mol ascorbate)-1 (kg chow) with r2=0.62.


CONCLUSIONS
Lens ascorbate concentration linearly increases with dietary ascorbate intake without cataract development in the rat. The currently presented method for sample preparation to measure the whole-lens content of ascorbate is applicable.
Mody
Vino C
VC
St. Erik's Eye Hospital, and Department of Physiology and Pharmacology, Division of Pharmacology, Karolinska Institutet, Stockholm, Sweden. vino.mody@ste.ki.se
Kakar
Manoj
M
Elfving
Ase
A
Söderberg
Per G
PG
Löfgren
Stefan
S
D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage* / Q000378:metabolism*; D001205:Ascorbic Acid / Q000008:administration & dosage* / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004032:Diet; D004435:Eating; D005260:Female; D007908:Lens, Crystalline / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013048:Specimen Handling
D000975:Antioxidants; D001205:Ascorbic Acid