title: Ascorbic acid uptake by young and aged guinea pig lenses.
abstract: The dynamics of in vitro uptake of [14C]-ascorbic acid into intact lenses of young (50 days old) and old (730 days old) guinea pigs was evaluated in this study. Two-dimensional protein gel analysis of [35S]-methionine labeled proteins provided evidence that the isolated lenses were viable throughout the culture period. It was found that the in vitro uptake of ascorbate into these lenses follows similar saturation kinetics for lenses from both age groups. Moreover, the linear uptake rate was identical. Ascorbate transport was inhibited by phloretin, p-chloromercuribenzoate, insulin, glucose and ouabain; however, no inhibition was observed with 2,4-dinitrophenol or NaF. These results suggest that the lenticular ascorbate concentration is regulated by a facilitated diffusion process and it not energy-dependent. Data on ascorbate transport into lenses from aged guinea pigs provide strong evidence that the abnormally low ascorbic acid concentrations in lenses of old mammals is not likely the result of a decreased lenticular uptake ability.
authors.affiliation: Sasakawa Center for Aging Research, Linus Pauling Institute of Science and Medicine, Palo Alto, California 94306.
authors.forename: J E
authors.initials: JE
authors.lastname: Fleming
authors.forename: S
authors.initials: S
authors.lastname: Choi
authors.forename: K G
authors.initials: KG
authors.lastname: Bensch
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D001205:Ascorbic Acid / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001692:Biological Transport; D005260:Female; D005947:Glucose / Q000494:pharmacology; D006168:Guinea Pigs; D007903:Lens Capsule, Crystalline / Q000737:chemistry / Q000378:metabolism*; D009924:Organ Culture Techniques
chemical_list: D005947:Glucose; D001205:Ascorbic Acid