Isoforms of Na, K‐ATPase in epithelial and endothelial barriers in the equine hoof

Abstract

Na, K‐ATPase is essential for the maintenance of intracellular sodium and potassium concentrations, thereby maintaining cell volume and electrochemical gradients. Currently, the presence and distribution of sodium pumps has not been characterised in equine hoof tissues. The aim of this study was to characterise the distribution of Na, K‐ATPase pump subunit isoforms within hoof lamellar keratinocytes and small vessels, as well as the digital artery supplying the hoof. Using various isoform specific monoclonal and polyclonal antibodies, we have examined the cellular localization of Na, K‐ATPase α1, α2, α3, β1, and β2, subunits within normal equine hoof tissues using immunohistochemistry. Moderate immunoreactivity for Na, K‐ATPase α1, α2, β1 and weaker staining for Na,K‐ATPase α3 was observed in the cytoplasm and plasma membrane of lamellar keratinocytes. All antibodies except α1 and α3 also demonstrated moderate to strong staining in the smooth muscle and endothelium of small vessels within the dermal hoof tissue. α3, β1, and β2 moderately stained the endothelium, smooth muscle and smaller vessels of the digital artery, while α2 stained only the smooth muscle and small vessels of the digital artery, with no staining observed for α1. These results confirm that Na, K‐ATPase isozymes are present in the equine hoof and may play a functional role in maintaining electrochemical gradients across its epithelial and endothelial barriers. This research was supported by the University of Nottingham.