Dietary L-Carnitine Protects the Gills and Skin of Guppies ( Poecilia reticulata) Against Anionic Xenobiotics

Abstract

L-carnitine is a carrier of activated fatty acids into mitochondria, but it may also have other functions. Experiments were conducted to investigate possible influences of dietary L-carnitine at the cellular level. Contact fluorescent microscopy was used to compare the responses of tissues of fish fed different levels of dietary L-carnitine when exposed to the fluorescent markers fluorescein and acridine orange. The penetration and accumulation of these markers in living cells was estimated by measuring the intracellular intensity of their fluorescence (530 nm). The results showed that penetration of fluorescein from water via gills was significantly lower in L-carnitine fish than in control fish. Intact plasma membranes are almost impermeable to organic anions, such as fluorescein, but damage of plasma membranes increases their permeability. Thus, it appears that the membranes of L-carnitine fish may be better protected against the penetration of anionic xenobiotics than the membranes of control fish. Accumulation of acridine orange, a cationic compound, did not show any significant differences between L-carnitine fish and control fish. Organic cations penetrate plasma membranes via diffusion, and this is unlikely to be influenced by L-carnitine.