The ontogeny of electrical activity associated with absorption of solutes across the developing small intestine of the chick (Gallus domesticus).

1. Electrical potentials across the developing intestine of the chick were measured in vitro 3-4 days before and up to 32 days after hatching.2. Embryonic intestine had a very high endogenous p.d. (serosa positive to mucosa) which decreased up to hatching. This decrease continued during intestinal maturation, reaching a basal level several days after hatching.3. Transfer potential differences were caused only by the actively transferred hexoses both in embryonic and post-embryonic intestine. These potentials decreased concomitantly with the decrease in the endogenous p.d. Kinetic analysis showed that the ;apparent K(m)' of glucose for the glucose transfer p.d. generating mechanism did not change over the period of hatching.4. Both the embryonic and post-embryonic transmural p.d. either in the presence or absence of metabolizable hexose was dependent upon aerobic metabolism.5. The transmural p.d. of hatched chick small intestine (with and without hexoses) was linearly related to log(10)[Na(+)] of the mucosal fluid. The magnitude of the glucose transfer p.d. both in embryonic and post-embryonic small intestine, however, was not lowered by decreasing the mucosal [Na(+)].6. Amino acid transfer potentials were of small magnitude at all stages of development.