Year-end Sale % OFF 
Abstract
Abstract Rats fed a diet lacking calcium adapt to this deprivation by increased active transport of this ion across the intestine. When the characteristics of the transport system were analyzed in vitro by use of saturation kinetics, increased net absorptive calcium transport appeared to be the result of an increased affinity (decrease in Kt from 1.12 to 0.59 mm) rather than an increase in the capacity or Vmax of the transport process. Adaptation through substrate induction in yeast results in an analogous increase in carrier affinity for sugar transport by a linkage to metabolic energy. Such a mechanism could account for the lowered dietary calcium effect, however the authors suggest that rather than an actual change in carrier affinity a second molecule (such as intestinal calcium-binding protein) could also alter carrier-substrate equilibria and produce a decrease in the observed Kt if access to the carrier were rate limiting at low substrate concentrations and this second molecule increased access of substrate. This model is consistent with the changes in calcium transport system characteristics and calcium-binding protein levels under conditions of restricted dietary calcium levels.
Highlights
Rather than an increase in the capacity or Vm, of the transport process
We hi;e previously shown that net movement of calcium from the mucosal to serosal side of the tissue against this potential difference is compatible with thermodynamic criteria for active transport [7]
We will show that use of the Michaelis-Menten kinetic model may be an oversimplification
Summary
Rather than an increase in the capacity or Vm,, of the transport process. Adaptation through substrate induction in yeast results in an analogous increase in carrier affinity for sugar transport by a linkage to metabolic energy. Such a mechanism could account for the lowered dietary calcium effect, the authors suggest that rather than an actual change in carrier affinity a second molecule (such as intestinal calcium-binding protein) could alter carriersubstrate equilibria and produce a decrease in the observed
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
