Examination of the origin of increased equine serum alkaline phosphatase concentrations.

The research examines the origin of increased serum alkaline phosphatase in horses, finding that most of it seems to come from bone tissue. It’s based on an examination of equine samples from the Ontario Veterinary College over 18 months, using sensitivity to L-phenylalanine and heat to try to determine the enzyme’s origin.

Study Overview and Context

• The research was motivated by the observation that over 32% of equine serum samples analyzed at the Ontario Veterinary College over an 18 month period showed higher than normal concentrations of alkaline phosphatase. Alkaline phosphatase is an enzyme, commonly found in several tissues including liver, bones, and kidneys, that plays a substantial role in regulation of proteins.
• An increased concentration of this enzyme in blood serum is frequently indicative of a health issue. In the veterinary context, this can signal potential liver or bone disorders in horses.

Research Methods and Approach

• To trace the origin of these increased enzymes, researchers tested the isoenzymes’ sensitivity to L-phenylalanine and heat. Isoenzymes are different forms of an enzyme that perform the same action but can originate from different tissues.
• This sensitivity study was conducted on 44 clinical cases that represented different health problems in horses and foals. This was intended to explore if the pattern of sensitivity differed across different diseases or conditions.

Findings and Conclusions

• Contrary to what might be expected if differing health problems induced differing patterns of alkaline phosphatase production, the research found no difference in sensitivity to either L-phenylalanine or heat across the clinical cases studied. That is, the increased activity of the enzyme didn’t change regardless of the kind of health problem the horse had, or the age of the horse.
• However, the primary finding was that the excess alkaline phosphatase mainly came from bone tissue, regardless of health problem or the age of the horse. This suggests any condition or disorder that affects bone metabolism in horses can potentially lead to increased concentrations of this enzyme in the blood serum.