Encystation of axenically grown Entamoeba histolytica: effect of bacterial endotoxins, starch and epinephrine

Abstract

Axenically grown trophozoites of Entamoeba histolytica, starch fed and toxin treated, when incubated in a minimal medium containing epinephrine and theophylline at 33° ± 1° C were transformed to a round form with a thick outer wall; in contrast, the untreated cells died. These round bodies or "precysts" hatched to the trophic form when transferred to fresh growth medium. Formation of round bodies occurred even in the absence of cysteine but they were not mature and readily disintegrated. The starch treated cells possessed nearly twice the activity of amylase as present in the control cells. The activity of glycogen phosphorylase was comparable in the control and starch fed cells. Glycogen synthetase activity was not detected in the control or starch fed cells. Axenically grown cells did not accumulate DL (7-³H) epinephrine, but after feeding on starch the cells accumulated the amine readily which was found distributed almost equally between the particulate fraction and the particulate-free cytoplasm. The uptake of epinephrine was significantly inhibited by propranolol, a β -adrenergic blocker but not by phentolamine, an α-adrenergic blocker. The amine was bound to the protein fraction of the particulate material.