Plasma histamine levels in laminitic horses and in horses treated with a corticosteroid.

This research investigated the levels of histamine, a compound involved in local immune responses, in horses suffering from laminitis, a painful disease affecting horse’s hooves. It also explored how the administration of a specific corticosteroid affects this level. The study found that histamine levels were significantly higher in laminitic horses compared to healthy ones, while the tested steroid did not alter histamine levels.

Method of Evaluating Histamine Levels

• In this study, the histamine levels in the plasma of horses were quantified using a radioenzymatic method that employs the enzyme histamine-N-methyltransferase.
• The concentration of histamine in healthy horses, also known as “sound horses”, was measured as the mean and standard deviation (mean = 4.46 nmol/l, SD = 1.55 nmol/l).

Histamine Levels in Laminitic Horses

• Samples from 11 horses suffering from laminitis, a painful and debilitating condition affecting horse’s hooves often resulting from inflammation, were tested using the same method.
• Remarkably, the levels of histamine in the plasma of these horses were found to be higher (mean = 12.46 nmol/l, SD = 3.24 nmol/l), indicating a significant difference when compared to healthy horses.

Effect of Corticosteroid on Histamine Levels

• The study also investigated the impact of a corticosteroid, dexamethasone-21-isonicotinate, on plasma histamine level.
• This corticosteroid was administered in a dosage of 10 mg per 100 kg of body weight, twice to three healthy horses.
• The histamine levels in these horses were then monitored over a two-week period.
• Interestingly, the steroid treatment did not seem to change the histamine levels which remained within the range observed for sound control horses, demonstrating that dexamethasone-21-isonicotinate did not affect histamine levels under these conditions.