Pharmacodynamic evaluation of the effects of oral melatonin on expression of the T-cell cytokines interleukin-2 and interferon gamma in the dog.

Abstract

To determine the effects of exogenous melatonin administration on activated whole blood expression of the T-cell cytokines interleukin-2 (IL-2) and interferon gamma (INF-γ) in dogs. Ten healthy dogs. Heparinized whole blood was collected from 10 dogs for analysis of cytokine expression before administration of melatonin (baseline). Each dog was then administered melatonin at a dosage of approximately 1mg/kg, PO, q 12hr for 14days. On day 14, whole blood was again collected from each dog at the time points of trough (0hr) and 6hr postmelatonin administration to evaluate the effects of melatonin on cytokine expression. At all evaluated time points, analysis of activated whole blood expression of mRNA coding for both IL-2 and IFN-γ was performed using quantitative reverse transcription polymerase chain reaction to determine whether a difference existed for any time point. Blood melatonin concentrations were also measured at comparable time points. A statistical difference in the expression of either cytokine was not appreciated at any time point, despite attainment of expected blood concentrations of the drug. Results indicate that melatonin therapy does not significantly affect IL-2 or IFN-γ expression in healthy dogs. While melatonin is thought to have an effect on the immune system in dogs, it does not appear this effect is through altering T-cell IL-2 or IFN-γ expression. Further studies investigating the effects of melatonin on the immune system of dogs are warranted.