In vitro studies on intestinal calcium and phosphate transport in horses.

The research article evaluates the intestinal transport and absorption of major minerals like calcium and phosphate in horses. It employs an in vitro method using radioisotope tracers to investigate the molecular mechanisms that govern how these minerals are absorbed in different segments of the horse’s intestine.

Objective and Methodology

• The study’s objective was to better understand calcium (Ca(2+)) and inorganic phosphate (P(i)) transport in the horse’s gastrointestinal tract.
• Due to the widespread prevalence of intestinal disorders in horses that result in imbalances in the absorption and secretion of calcium and phosphate, this study was conducted.
• The researchers used the in vitro radioisotope tracer technique with Ussing chambers to characterize the intestinal Ca(2+) and P(i) transport functionally.

Main Findings

• The study found that among the different intestinal segments, the duodenum – the first part of the small intestine – showed the highest active absorption of calcium.
• Through reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis, the research identified potential components involved in the active transcellular transport of calcium.
• These components include the epithelial calcium channel named TRPV6, the cytosolic calcium binding protein known as calbindin-D(9K), and the plasma membrane calcium ATPase termed PMCA.

Phosphate Transport

• The research provides insights into phosphate transport, indicating significant active phosphates secretion in the jejunum, which is the middle section of the small intestine.
• The mechanisms contributing to such phosphate transport in the jejunum were not clear from this study.
• The study did discover that the use of ouabain, an antagonist of the basolateral Na(+)/K(+)-ATPase, significantly inhibits serosal-to-mucosal phosphate transport, meaning that sodium levels can play a significant role in jejunal phosphate transport in horses.