Origin an importance of increased alkaline phosphatase activity in peritoneal fluids of horses with colic.

The researchers studied the reasons behind the increased activity of alkaline phosphatase (ALP) in the peritoneal fluid of horses experiencing colic. They found that the enzyme ALP in the fluid primarily came from granulocytes, a type of white blood cell, rather than from small intestinal injuries.

Research Purpose and Methods

• This study aimed to investigate the source of increased alkaline phosphatase (ALP) activity in equine peritoneal fluid (a fluid in the stomach cavity). This was important due to the observation that horses with abdominal pain symptoms demonstrated higher ALP activity. Identifying the origin of the increased ALP would provide insights into its diagnostic value for small intestinal injuries in horses.
• The researchers compared ALP isoenzymes in peritoneal fluid from 10 healthy horses and 50 horses with acute abdominal pain. The study looked at how these enzymes reacted to inhibitors like L-phenylalanine, L-homoarginine, and levamisole, and to heat inactivation. These enzymes were also differentiated based on their migration patterns during a technique called polyacrylamide gel disc electrophoresis.

Findings and Implications

• 20 out of the 50 horses with colic had abnormally high levels of ALP activity in their peritoneal fluids, 10 of which demonstrated marked increases of ALP activity, from 10 to 150 times the normal range.
• Interestingly, ALP values in serum samples from these horses were within the normal range, suggesting that the elevated ALP was predominantly present in the peritoneal fluid.
• In 19 out of these 20 horses, the properties of the ALP in the peritoneal fluid differed from those found in the small intestine, indicating a different origin.
• Of the 10 peritoneal fluid samples with extremely high ALP activity, nine displayed properties typical of granulocytic ALP, indicating that the ALP originated from granulocytes – a type of white blood cell. This suggests that the increased ALP activity in these horses may be linked to an immune response.
• Different clinical conditions were diagnosed in these horses, including thromboembolic colic, colonic torsion, small intestinal volvulus, peritonitis, and salmonellosis.
• Of the 50 horses with colic, six had severe small intestinal disease but did not show increased ALP activity in their peritoneal fluid.
• These findings indicate that increased ALP activity in the peritoneal fluid may not be a reliable indicator of small intestinal injury in horses, as initially hypothesized. The increased ALP appears to be predominantly granulocytic and might be more related to an immune response rather than intestinal injury.