Mannitol metabolism in Eimeria tenella.

, and 1992. Mannitol metabolism in Eimeria tenella. International Journal for Parasitology 22: 1157–1163. Unsporulated oocysts of Eimeria tenella contain large quantities of carbohydrates, namely amylopectin, mannitol and glucose. Analysis of the carbohydrate content of sporulating oocysts revealed that mannitol content increased markedly during early stages of sporogony (first 4–6 h) but slowly diminished during the next 40 h of sporulation. Accumulation of mannitol was accompanied by a rapid decrease in amylopectin and free glucose, suggesting that mannitol might be synthesized from glucose released from amylopectin. Mannitol was also detected in sporozoite and merozoite extracts. All four mannitol cycle enzymes were detected in oocysts. Sporozoites excysted in vitro had lower activities of all four enzymes. Mannitol-1 -phosphatase and mannitol dehydrogenase activity was also detected in merozoites obtained from the second stage schizonts. Sporozoites incubated with ¹⁴C-glucose accumulated radioactively labelled precursor continuously for over 12 h and some of the ¹⁴C-glucose was converted into ¹⁴C-mannitol. These results indicate that mannitol plays an important role in the metabolism and development of the intracellular stages of the parasite.