Related Experiment Video
Updated: Jul 20, 2026

Models and Methods to Evaluate Transport of Drug Delivery Systems Across Cellular Barriers
Published on: October 17, 2013
Modeling of transcellular Ca transport in rat duodenum points to coexistence of two mechanisms of apical entry
1Department of Physiology, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
Abstract:
Employing realistic parameters, we have demonstrated that a relatively simple mathematical model can reproduce key features of steady-state Ca2+ transport with the assumption of two mechanisms of Ca2+ entry: a channel-like flux and a carrier-mediated transport. At low luminal [Ca2+] (1-5 mM), facilitated entry dominates and saturates with Km = 0.4 mM. At luminal [Ca2+] of tens of millimolar, apical permeability is dominated by the channel flux that in turn is regulated by cytosolic Ca2+. The model reproduces the linear relationship between maximum Ca2+ transport rate and intestinal calbindin D9K (CaBP) content. At luminal [Ca2+] > 50 mM, local sensitivity analysis shows transcellular transport to be most sensitive to variations in CaBP. At low luminal [Ca2+], transport becomes sensitive to apical entry regulation. The simulations have been run within the Virtual Cell modeling environment, yielding the time course of external Ca2+ and spatiotemporal distributions of both intracellular Ca2+ and CaBP. Coexistence of two apical entry mechanisms accords with the properties of the duodenal Ca2+ transport protein CaT1 and the epithelial Ca2+ channel ECaC.
Related Concept Videos
Transcellular Transport of Solutes
Introduction to Membrane Traffic
The transport of soluble and membrane proteins is mediated by transport vesicles that collect cargo from one cellular compartment and deliver it to another by fusing with the target organelle membrane. The Rab...
Glucose Absorption Into the Small Intestine
Transport Across the Golgi
Reabsorption and Secretion in the DCT and Collecting Duct
The distal part of the DCT, along with the...
Mechanisms of Drug Absorption: Paracellular, Transcellular, and Vesicular Transport
However, most drugs use the transcellular route, traversing directly through the cell membranes via two mechanisms: passive and active transport. Passive...

