DIETARY L-CARNITINE PROTECTS THE GILLS AND SKIN OF GUPPIES (POECILIA-RETICULATA) AGAINST ANIONIC XENOBIOTICS

L carnitine is a carrier of activated fatty acids into mitochondria, b ut it may also have other functions. Experiments were conducted to inv estigate possible influences of dietary L-carnitine at the cellular le vel. Contact fluorescent microscopy was used to compare the responses of tissues of fish fed different levels of dietary L-carnitine when ex posed to the fluorescent markers fluorescein and acridine orange. The penetration and accumulation of these markers in living cells was esti mated 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 anion s, 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 xenobiotic s 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 m embranes via diffusion, and this is unlikely to be influenced by L-car nitine. (C) 1997 Elsevier Science Inc.