Cholesterol metabolism in Asterias rubens

[4-C-14] cholesterol [26-C-14] cholesterol and [2-C-14] acetic acid were em ployed to study cholesterol metabolism in A. rubens. With [4-C-14] choleste rol highest radioactivity was found in free sterols (71%) and steryl esters (24%) and smallest in glycerides and free fatty acids. sterol sulphate wer e rico heavily labelled Fatty acid methyl eaters prepared from glycerides a nd free fatty acids contained negligible radioactivity. Incorporation of [26-(14)-C] cholesterol also resulted highest label in fre e sterols (75%) and steryl eaters (19%). Saponification of steryl esters di d not yield activity into fatty acid while sterols were labelled Again ster ol sulphates were labelled heavily. Incubation with [2-C-14] acetic acid recorded highest activity in triglycer ides (72%) and steryl esters (16%) while free sterol were significantly lab elled (5%). Moreover, situation of label in steryl esters and free sterols was opposite to that of [4-C-14] cholesterol. Cholesterol catabolism did not produce labelled precursors or support re-ut ilization of carbon for lipid/cholesterol synthesis.