Intestinal α-glycosidase transcriptional responses during development and diet adjustment in altricial birds

We describe developmental changes in maltasic activity and its mRNA until adulthood, and in response to an increase in dietary starch. We studied house sparrows (Passer domesticus), which undergo a natural switch from insects to a starch-containing seed diet during development, and zebra finches (Taeniopygia guttata), which have a relatively fixed starchy seed diet during development. In zebra finches, in which maltasic activity increased with age but not with dietary starch, α-glycosidase (AG) mRNA was not affected by either age or dietary starch level. In house sparrow nestlings, in which maltasic activity increased with age and with added starch, AG mRNA was higher when birds were fed a diet with added starch but did not increase with age. These results are consistent with the idea that the apparent programmed developmental increase in maltasic activity is not mainly under transcriptional control of AG mRNA, whereas induction of maltasic activity by increased dietary starch is.