Date of Award


Degree Type


University or Center

Atlanta University (AU)

Degree Name




First Advisor

Gordon J. Leitch


Axenically cultured Entamoeba histolytica trophozoites of the pathogenic strain HM-1 were harvested in phosphate buffered saline (PBS). The cells were disrupted with ultrasonic energy, centrifuged, and the supernatant fluid tested for enterotoxic activity in the i[n vivo rabbit ileum loop .and-the rat proximal colon loop. This HM-1 extract, equivalent to 106 trophozoites/ml, had no effect on intestinal absorption in either animal model, but secretion resulted in both preparations when indomethacin (0.1 mg/kg) was administered subcutaneously to reduce cytoprotection. In the rat colon a lower dose of indomethacin was ineffective in allowing the ameba preparation to cause frank secretion, while higher doses, 1 and 10 mg/kg, directly inhibited this secretory response. In the absence of indomethacin, a preparation equivalent to 107 trophozoites/ml reduced colonic absorption without producing secretion, while a preparation of 107 trophozoites/ml of the non-pathogenic E_. histolytica-like Laredo strain was ineffective even in the presence of 0.1 mg/kg indomethacin. The HM-1 enterotoxic activity was heat labile. Prior exposure of the loop lumen to fetuin (100 wg/ml) blocked the secretory response to subsequent enterotoxin exposure in indotnethacin-treated animals. Fetuin inhibition of secretion could not be reversed by inoculating the loop with fresh trophozoite extract at hourly intervals for 4 hours.

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