Researchers from the United Kingdom report there is a decrease in contractile function of the aortic valve with age, resulting in aortic valve disease.

Mark Bowen, BVetMed CertVA CertEM(IntMed) MRCVS, an associate professor in veterinary internal medicine at Nottingham Vet School, said, "Our aim was to define what is normal in the aging horse population."

He and his colleagues examined 142 valves from a local slaughter house. The valves were grouped by the age of the animal from which each came. The researchers measured the contractile function, collagen content, and content of a contractile protein in each valve in vitro (not in the live animal, but in the laboratory).

The contractile force decreased with increasing age, and horses older than 15 had significantly higher concentrations of hydroxyproline (a marker for collagen content) in their valves. Bowen said there is ongoing work to determine whether the increased collagen causes the reduction in contractile function, or whether the increased collagen is a natural response to a reduction in function