Sodium and glucose transport across the in vitro perfused midgut of the blue crab, Callinectes sapidus Rathbun
Chu, Ka Hou
MetadataShow full item record
The principal objectives of the present study are: (1) to investigate sodium transport across the midgut as well as the hindgut of Callinectes sapidus and the functioning of these two regions of the gut in osmotic and ionic regulation of the animal, and (2) to elucidate the mechanism of glucose absorption across the midgut of C. sapidus and to assess its role in nutrient absorption. The transport processes across the gut tissues were studied with an in vitro perfusion technique. I demonstrated a net mucosal to serosal sodium transport across the midgut of C. sapidus. This net flux was within the same order of magnitude as the fluxes of isolated gut tissues of many other animal species. The flux displayed saturation kinetics and was ouabain-sensitive. The flux did not vary with environmental salinity, thus providing no evidence for an active regulatory role of the midgut in sodium balance. A reduction of passive permeability with salinity, however, was suggested. There was no measurable net sodium transport across the hindgut of the animal. The midgut of C. sapidus was also capable of net transmural glucose absorption. The net flux was considerably less than the fluxes reported in mammalian intestine. The unidirectional mucosal to serosal glucose flux was depressed by metabolic inhibitors, the absence of mucosal Na+, and the presence of mucosal phlorizin or serosal ouabain. The flux was also decreased by the presence of mucosal D-galactose, but not D-fructose or L-glucose. The net glucose flux followed Michaelis-Menten kinetics. The mucosal glucose uptake by the midgut was composed of two processes: a sodium-dependent, saturable component, and a sodium-indenpendent, non-saturable counterpart. The kinetic characteristics of the uptake suggest that the midgut does not play a major role in total nutrient absorption. Nutrients taken up by the midgut may be largely utilized to provide energy for other physiological functions served by this tissue. Thin layer chromatographic analyses showed that whereas most glucose appeared as phosphorylated forms upon entering the midgut, free glucose was translocated across the tissue. These results suggest that the mucosal and serosal membrane transport processes are coupled to phosphorylation-dephosphorylation mechanisms, respectively. An alternative hypothesis is the presence of a high-affinity glucose carrier in the serosal border of the midgut.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution January 1984
Showing items related by title, author, creator and subject.
Biological-physical interactions on Georges Bank : plankton transport and population dynamics of the ocean quahog, Arctica islandica Lewis, Craig V. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1997-06)Advective losses of bank water during winter because of strong wind forcing were hypothesized to be a significant factor limiting recruitment of Georges Bank cormnunities. This hypothesis was examined using biological-physical ...
Evolution of oceanic margins : rifting in the Gulf of California and sediment diapirism and mantle hydration during subduction Miller, Nathamiel C. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2013-06)This thesis investigates three processes that control the evolution of oceanic margins. Chapter 2 presents seismic images of a ~2-km-thick evaporite body in Guaymas Basin, central Gulf of California. In rifts, evaporites ...
Silverthorne, Katherine E. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-06)Observational and modeling techniques are employed to investigate the thermal and inertial upper ocean response to wind and buoyancy forcing in the North Atlantic Ocean. First, the seasonal kinetic energy variability of ...