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The effect of Giardia lamblia trophozoites on trypsin, chymotrypsin and amylase in vitro

Published online by Cambridge University Press:  06 April 2009

F. Seow ,
P. Katelaris  and
M. Ngu
F. Seow
Affiliation:
Gastroenterology Unit, Repatriation General Hospital, Concord 2139, Sydney, Australia
P. Katelaris
Affiliation:
Gastroenterology Unit, Repatriation General Hospital, Concord 2139, Sydney, Australia
M. Ngu
Affiliation:
Gastroenterology Unit, Repatriation General Hospital, Concord 2139, Sydney, Australia
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Summary

Giardia lamblia localize and multiply in the small intestine and may cause acute or chronic diarrhoea with malabsorption of fat, protein and other nutrients. Abnormal pancreatic function has been documented in giardiasis and trophozoites directly inhibit pancreatic lipase activity in vitro. The aim of this study was to examine the effect of Giardia trophozoites on pancreatic trypsin, chymotrypsin and amylase activity in vitro. Axenically cultured Giardia trophozoites (Portland-1 stock) were incubated with a range of concentrations of trypsin, chymotrypsin and amylase and enzyme activity assayed over time. Tryptic activity was decreased after incubation with Giardia trophozoites. This reduction was time dependent and linear over the incubation period of 2 h. At a trypsin concentration of 18 BAEE units/ml, there was a 35.5±4% reduction in enzyme activity after 2 h compared to controls. The total amount of activity lost was proportional to the initial trypsin concentration up to 185 BAEE units/ml. At this initial concentration, the activity was reduced by 46.5±3 units/ml after 2 h. Above this concentration, little further loss of enzyme activity was seen. To investigate the nature and specificity of this effect, similar experiments were conducted using killed trophozoites and with a related protozoan. Trichomonas vaginalis. No loss of enzyme activity was evident. Media previously incubated for 2 h with trophozoites did not diminish tryptic activity. Trophozoites had no effect on chymotrypsin or amylase activities over the range of concentrations tested. Giardia trophozoites directly diminish pancreatic tryptic activity in vitro, by an active process which appears specific and not mediated via a secretory product. This mechanism may enhance parasite survival in the small intestine by allowing trophozoites to escape destruction by luminal proteases and may also contribute to malabsorption.

Keywords

Giardia lambliatrypsinchymotrypsinamylasepancreatic functionmalabsorption
Type
Research Article
Information
Parasitology , Volume 106 , Issue 3 , April 1993 , pp. 233 - 238
Copyright
Copyright © Cambridge University Press 1993

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