ABSTRACT
The isolated midgut of the adult blowfly, Calliphora vicina, can be maintained under internal perfusion for over 6h, and calcium absorption measured by including 45Ca in the perfusing saline with [3H] inulin as a volume marker. The midgut has a considerable capacity to transport calcium from the lumen (L) to the bathing saline (BS) against its electro-chemical gradient and in the absence of an appreciable net water flux across the gut. Calcium absorption (L-BS) shows saturation kinetics, is totally and reversibly inhibited by metabolic poisons and is accompanied by a negligible backflux (BS-L). It is concluded that the midgut of C. vicina is capable of active calcium transport and that the entire transepithelial calcium flux occurs via a transcellular route. This contrasts with the mammalian duodenum, where absorption occurs via a combination of transcellular and paracellular routes.
