Messenger RNA expression and immunolocalization of psoriasin in the goat mammary gland and its milk concentration after an intramammary infusion of lipopolysaccharide.

Psoriasin (S100A7) is a member of the S100 protein family of calcium-binding proteins and plays a crucial role in local host defenses. The present study aimed to identify the expression of S100A7 in the goat mammary gland and in milk. The goat S100A7 coding DNA sequence was identified using direct sequencing. An S100A7 antibody was raised in rabbits by immunization with a synthetic S100A7 peptide consisting of 13 amino acids. Messenger RNA expression and protein localization in different regions of a healthy mammary gland were detected by reverse transcription-polymerase chain reaction and immunohistochemistry. Changes in the concentration of S100A7 in the milk after an intramammary infusion of Escherichia coli lipopolysaccharide (LPS) were examined by an enzyme immunoassay. The goat S100A7 peptide had 98% and 86% sequence similarity to that of sheep and bovines, respectively. The S100A7 mRNA expression was higher in the teat and udder skin than in the cistern and parenchyma of the mammary gland. Immunoreactive S100A7 was localized in the epithelial cells of the alveolus and gland cistern, and stratified squamous epithelium of the teat. Psoriasin as a secreted protein was detectable in healthy milk, and an intramammary LPS infusion increased the concentration of S100A7 in the milk. The results suggest that S100A7 is produced in the epithelial cells of the mammary gland and is secreted into the milk.