Flow Cytometric Analysis of Eimeria tenella Sporozoites Exposed to Nigericin, Monensin and Lasalocid In Vitro

Abstract

Loss of membrane integrity and intracellular esterase activity in Eimeria tenella sporozoites after exposure to polyether ionophorous antibiotics lasalocid (LAS), monensin-Na (MON) and nigericin (NIG) were analysed by means of flow cytometry (FCM) using one-dimensional frequency distribution of measured intracellular fluorescein fluorescence (520nm) and propidium fluorescence (640nm), respectively. The polyether antibiotics were dissolved in dimethylformamide (DMF) and adjusted to concentrations of 100, 10, 1 and 0.1 μg/ml by dilution with medium 199. Thereafter, freshly excysted sporozoites were exposed to the above mentioned drug concentrations for 20, 40 and 70min and analysed by FCM. Compared with the DMF (1%) control, sporozoites exposed to 100 μg/ml LAS for 20min showed a strong reduction of esterase activity and a high degree of membrane damage, as well as 10μg/ml LAS after 70min incubation. NIG had a similar activity profile with respect to membrane damage indicating that this polyether is a powerful ionophore in killing E. tenella sporozoites in vitro. In contrast, MON which is known to be a strong anticoccidial in vivo, exhibited only a weak effect on sporozoites in vitro, and there was a time and dose-dependent decrease of sporozoites showing enhanced esterase activity but no membrane damage.