The expression of histamine H ₄ receptor mRNA in the skin and other tissues of normal dogs

The histamine4 (H ₄) receptor was first cloned and characterized in 2000 using the human H ₃ receptor DNA sequence. The H ₄ receptor has been shown to participate in various aspects of inflammation, such as chemotaxis, upregulation of adhesion molecule expression and modulation of cytokine secretion. The primary goal of this study was to determine whether H ₄ receptor mRNA is expressed in normal canine skin by performing an RT-PCR. An additional goal was to determine the expression of this receptor in the colon, liver, spleen and kidney. Tissues were collected from five healthy, young-adult pit bull dogs. Samples were immediately placed in RNAlater ^® solution and stored at -20°C until processed. The amplified products in all skin samples in addition to the colon, liver, spleen and kidney (variable expression) had the expected size of 400-500bp. The sequenced amplicons matched the National Center for Biotechnology Information published sequence for the canine H ₄ receptor. The study results showed that canine normal skin expresses the H ₄ receptor mRNA. Further studies using immunohistochemistry should be conducted to demonstrate the expression of the H ₄ receptor at the protein level and to localize the expression of this receptor in the skin.