The Kinetics of Fatty Acid Uptake By Paramecium Tetraurelia

Abstract

The kinetics of radiolabeled fatty acid uptake by the ciliate Paramecium tetraurelia was examined on a homologous series of saturated, straight chain fatty acids of even carbon numbers. Uptake rates increased with chain length from acetate to palmitate. Saturation kinetics was demonstrated for most fatty acids examined, thus ruling out simple diffusion as the major mechanism for fatty acid transport and implicating carrier-mediated, facilitated transport as the major mechanism. Data from most competitive inhibition experiments were too scattered to determine the number of transporter systems present. Cholesterol uptake also exhibited saturation kinetics and hence other sterols, which can satisfy this nutritional requirement, may also be transported by a carrier-mediated mechanism. The uptake of the essential fatty acid oleate was faster than those observed for the saturated acids and could not be explained by only one transport mechanism. Therefore, fatty acid transport also occurs via other kinetically significant routes.

Mapping cholesteryl ester analogue uptake and intracellular flow in Paramecium by confocal fluorescence microscopy

“…There are numerous and extensive studies on phagocytosis in Paramecium (reviewed by Fok & Allen, 1990, 1993; Allen & Fok, 2000), whereas only a few papers have been devoted to fluid phase and receptor‐mediated endocytosis (Wyroba, 1991; Allen et al ., 1992; Ramoino et al ., 2001) or to lipid internalization (Kaneshiro et al ., 1989; Reuter et al ., 1989, 1993). By studying the kinetics of radiolabelled fatty acid incorporation, it was found that the rate of fatty acid uptake is unrelated to the rate of food vacuole formation (Reuter et al ., 1993). Furthermore, using a fluorescent fatty acid (1‐pyrenedodecanoic acid), Kaneshiro et al .…”