Trans- and paracellular calcium transport along the small and large intestine in horses.

The research investigates how calcium is absorbed in the intestines of horses, mapping mechanisms such as paracellular and transcellular transport and identifying novel proteins involved in calcium regulation. The study offers insights into the unique aspects of equine calcium homeostasis.

Overview of the Research

• The focus hinges on understanding intestinal calcium absorption, a process that plays a significant role in maintaining calcium balance in the body. Absorption occurs through paracellular or transcellary means – two distinct routes along which substances move between or through cells.
• The research builds upon the understanding that horses exhibit unique characteristics concerning calcium homeostasis (internal balance), with high absorption capacities, plasma calcium concentrations, and renal excretion combined with low plasma concentrations of vitamin D metabolites.
• Prior studies suggested that horses’ intestinal calcium transport is less reliant on vitamin D compared to other species. However, other potential regulatory mechanisms are not well-documented, creating the gap this research aims to fill.

Horses’ Unique Calcium Homeostasis

• Horses exhibit peculiarities not always present in other species, such as greater intestinal absorption of calcium, higher plasma calcium levels, greater renal excretion, and lower plasma Vitamin-D metabolite concentrations.
• Even though the specific mechanisms and regulations of intestinal calcium absorption in horses are largely unknown, previous research suggests that the transportation of intestinal calcium in horses isn’t as dependent on Vitamin D compared to other species.

Identification of Transport Mechanisms

• The study identifies paracellular and transcellular mechanisms for intestinal calcium transport along the intestinal axis in horses, employing the Ussing chamber technique, which is a classic approach to evaluate how substances are transported across epithelial tissues.
• The researchers document the expression of transport proteins associated with calcium absorption including transient receptor potential vanilloid member 6, calbindin-D and calcium ATPase type 1. This documentation is done alongside the measurement of calcium flux rates, the pace at which calcium ions move across a membrane.

Novel Regulatory Proteins for Calcium Homeostasis

• The research investigates novel regulatory proteins that may play a role in maintaining calcium homeostasis. These proteins – B-box and SPRY-domain containing protein, and calmodulin – are studied within equine intestinal tissues for the first time in this research.
• Identifying and understanding these proteins and their role in horse calcium absorption presents a new avenue for understanding equine calcium homeostasis regulation.