In vivo induction of endothelial P-selectin protein by VAP-1/SSAO. (A) VAP-1–deficient mice (KO) and VAP-1–deficient mice expressing human VAP-1 as a transgene (KO-TG) were fed 0.4% methylamine for 3 days in their drinking water. The expression of human VAP-1, mouse CD62P (P-selectin), and mouse CD62E (E-selectin) protein was stained using immunohistochemistry from the heart and mesenteric lymph node. (B) Partial overlap in VAP-1 and P-selectin expression (yellow) is seen in 2-color immunofluorescence images. (C) Quantitation of P-selectin expression in the mesenteric lymph nodes of VAP-1 KO mice and VAP-1 KO-TG mice that received methylamine (MA) in the drinking water for the indicated time period (days). Data (means ± SEM) are shown as semiquantitative scores ranging from 0 (negative) to 3 (high expression). n = number of mice per group. **P < .01.