Related Experiment Video

Updated: Aug 6, 2026

The Mesenteric Lymph Duct Cannulated Rat Model: Application to the Assessment of Intestinal Lymphatic Drug Transport
13:17

The Mesenteric Lymph Duct Cannulated Rat Model: Application to the Assessment of Intestinal Lymphatic Drug Transport

Published on: March 6, 2015

Magnesium transport across colon ascendens of the rat

U Karbach1

  • 1University of Munich, Medizinische Klinik Innenstadt, FRG.

Digestive Diseases and Sciences
|December 1, 1989
PubMed

Insights

The rat colon absorbs magnesium (Mg) similarly to calcium (Ca), with both ions utilizing separate cellular pathways and paracellular diffusion. Magnesium significantly reduces calcium absorption by decreasing diffusive flux.

Area of Science:

  • Physiology
  • Gastroenterology
  • Renal and Urological Physiology

Background:

  • Magnesium (Mg) and calcium (Ca) are essential divalent cations with complex absorption mechanisms.
  • The colon ascendens plays a role in electrolyte absorption, but its specific mechanisms for Mg and Ca transport are not fully elucidated.
  • Understanding these transport systems is crucial for managing electrolyte balance and related disorders.

Purpose of the Study:

  • To investigate the concentration and voltage dependence of unidirectional Mg fluxes across the rat colon ascendens.
  • To compare Mg and Ca transport mechanisms in the rat colon ascendens.
  • To determine the influence of Mg on Ca absorption and its underlying mechanism.

Main Methods:

  • Utilized a modified Ussing chamber to measure unidirectional Mg and Ca fluxes across rat colon ascendens.
  • Employed voltage clamp experiments and a paracellular marker (mannitol) to differentiate between cellular and diffusive transport.
  • Assessed the effect of varying Mg concentrations on Ca transport.

Main Results:

  • Mucosa-to-serosa Mg flux demonstrated a cellular component, while serosa-to-mucosa flux was purely diffusive.
  • Net Mg absorption occurred across the colon ascendens at physiological concentrations.
  • 5 mmol/liter Mg significantly decreased mucosa-to-serosa Ca flux by 70%, primarily by reducing diffusive Ca movement, not cellular transport.
  • Mg and Ca appear to be transported via separate cellular mechanisms, with paracellular diffusion being important for both.

Conclusions:

  • The rat colon ascendens actively absorbs Mg at rates comparable to Ca.
  • Mg transport involves a cellular component and paracellular diffusion.
  • Mg reduces Ca absorption by inhibiting its diffusive paracellular flux, possibly by affecting fluid absorption.
  • Separate cellular mechanisms exist for Mg and Ca transport in the rat colon, highlighting distinct physiological roles.

More Related Videos

Methods to Study Epithelial Transport Protein Function and Expression in Native Intestine and Caco-2 Cells Grown in 3D11:27

Methods to Study Epithelial Transport Protein Function and Expression in Native Intestine and Caco-2 Cells Grown in 3D

Published on: March 16, 2017

Demonstration of Membrane Transport of Histidine using Goat Intestinal Inverted Sacs: An Experiential Pedagogical Tool for Undergraduates04:40

Demonstration of Membrane Transport of Histidine using Goat Intestinal Inverted Sacs: An Experiential Pedagogical Tool for Undergraduates

Published on: October 4, 2024

Related Concept Videos

Transcellular Transport of Solutes01:23

Transcellular Transport of Solutes

Transcellular transport of solutes is the movement of substances like monosaccharides and amino acids through polarized cells. This transport mechanism is primarily seen in epithelial and endothelial cells aided by membrane transport proteins such as channels and transporters. The tight junctions between these cells confine the membrane proteins to the two sides of the cell. The epithelial cells have distinct apical and basolateral domains. In contrast, the endothelial cells show the luminal...
Glucose Absorption Into the Small Intestine01:26

Glucose Absorption Into the Small Intestine

Complex carbohydrates consumed cannot be absorbed into the small intestine in their original form. First, they must be hydrolyzed to a monosaccharide form such as glucose or galactose. These monosaccharides are then transported across the intestinal membrane and into the blood via transcellular transport. The intestinal epithelial cells allow the movement of these monosaccharides with a defined 'entry' through membrane transporter proteins present on their apical membrane and 'exit' via the...
Reabsorption and Secretion in the Loop of Henle01:17

Reabsorption and Secretion in the Loop of Henle

The thick ascending limb of the nephron loop has Na+–K+–2Cl− symporters in the apical membranes of its cells. These symporters simultaneously reclaim one sodium ion, one potassium ion, and two chloride ions from the tubular fluid. Sodium ions are actively transported into the interstitial fluid at the base and sides of the cell, diffusing into the vasa recta. Chloride ions move through leakage channels in the basolateral membrane into the interstitial fluid and then into the vasa recta.
Pore Transport and Ion-Pair Transport01:17

Pore Transport and Ion-Pair Transport

Pore transport and ion-pair formation are critical mechanisms for the absorption and distribution of drugs in the body.
Pore transport, also known as convective transport, is a process where small molecules like urea, water, and sugars rapidly cross cell membranes as though there were channels or pores in the membrane. Although direct microscopic evidence is limited  but the concept of pores or channels is widely accepted based on physiological evidence. Despite the lack of direct microscopic...
Carrier-Mediated Transport01:06

Carrier-Mediated Transport

Carrier-mediated transport is a pivotal process in drug absorption, particularly for lipid-insoluble drugs, and encompasses facilitated diffusion and active transport. Facilitated diffusion allows drugs to move along their concentration gradient without energy expenditure, while active transport utilizes ATP to drive drug movement against this gradient.
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...
Methods for Studying Drug Absorption: In situ01:09

Methods for Studying Drug Absorption: In situ

In situ experiments, such as the Doluisio method and Single-Pass Perfusion technique, provide critical insights into drug uptake by simulating in vivo conditions for drug absorption.
The Doluisio method involves perfusing a prepared segment of a rat's small intestine with a solution of radiolabeled drug and a non-absorbable marker. This helps to differentiate between absorbed and non-absorbed drug concentrations. The intestinal segment is connected at both ends using tubing and syringes,...