The Presence of L-Carnitine in Ocular Tissues of the Rabbit

Abstract

Carnitine plays an important role in the metabolism of fatty acids. Its presence is considerable in tissues that use fatty acids as an important source of energy, such as the heart and skeletal muscle. Free carnitine and acid soluble acylcarnitines are present in various tissues of the rabbit eye. The lowest concentration of carnitine was observed in the vitreous humor and the highest in the lens. The ratio, acid soluble acylcarnitine/free carnitine, was lower in the cornea, aqueous humor, vitreous humor and lens, than in iris, ciliary body and choroid-retina. The topical administration of carnitine increased both free carnitine and acetylcarnitine in cornea, and only free carnitine in aqueous humor and choroid retina. Only after intravenous administration, did the levels of free and acyl-carnitine increase in the iris and ciliary body. Neither of the two carnitine species was changed in vitreous humor. The determination of the activity of carnitine acetyltransferase in the eye showed that in the ciliary body the values of activity were three times higher than those in the iris and choroid-retina. The elevated ratio of acid soluble acylcarnitines with respect to free carnitine in iris, ciliary body, choroid-retina as well as the higher activity of carnitine acetyltransferase in the ciliary body, suggest that carnitine plays an important role in those tissues of the eye where cells of a muscular nature are present and may represent, after esterification, an important energy reserve.