PHYSICOCHEMICAL PROPERTIES AND METABOLISM OF LISSAMINE-RHODAMINE CERAMIDES - EFFECT OF ACYL-CHAIN LENGTH

The present report is a comparative study on physico-chemical properti es and metabolism of three different Lissamine-Rhodamine (LRh) derivat ives of ceramide (Cer), with twelve (C12-LRh-Cer), six (C6-LRh-Cer) ac yl linker spacers or with the fluorescent probe directly linked to the sphingosine moiety (C0-LRh-Cer). Transfer kinetics of the LRh-ceramid es from water dispersion, albumin complex and donor vesicles to accept or liposomes followed a double-exponential curve. Among the three cera mides, C12-LRh-Cer showed the lowest mobility. All ceramides were take n up by human fibroblasts and, with the exception of C0-LRh-Cer which was not metabolised, fluorescent sphingomyelin (SM) was the only detec table metabolite. Despite its low incorporation, C12-LRh-Cer was conve rted to the corresponding C12-LRh-SM with an efficiency roughly three times higher than that of C6-LRh-Cer. 'In vitro' enzymatic assays usin g cell homogenate gave similar results. These data indicate that C12-L Rh-Cer is the best mimic of the natural ceramide. (C) 1998 Published b y Elsevier Science Ireland Ltd. All rights reserved.