Effects of diet on amylase expression in the mosquitofish

Diets high in various carbohydrates were fed to mosquitofish,Gambusia affinis holbrooki, to determine the effects on amylase expression. Both amylase activity and amount of amylase protein were used as measures of amylase expression. Fish were fed for 21 days in one experiment, seven days in a second experiment and 24 h in a third. The first experiment compared responses of fish fed on a high-starch diet relative to a control diet. The second and third experiments compared responses on four diets relative to the control diet: maltose, starch, glucose, and glucose + cyclic adenosine monophosphate (cAMP). In the first two experiments whole visceral extracts were used. In the third experiment, gut and hepatopancreatic extracts were examined separately. Diet had a significant affect on the amount of amylase in all three experiments but affected amylase activity only in the 24 h experiment. Generally, glucose decreased amylase expression while maltose or cAMP + glucose increased it. Length of feeding period and tissue type also had significant effects on amylase expression.