NRP-1 protein expression in human colon epithelial cells. The percentage of NRP-1 positive staining cells was calculated in crypts in the field and mid-sigmoid samples. (A) Graphs showing no relationship between butyrate concentration and NRP-1 expression in the field (contra-lateral) but a strong inverse correlation at the mid-sigmoid (r = -0.622; p = 0.001) (B) Graph showing the data as mean ± SEM when grouped into tertiles according to butyrate concentration. In the contra-lateral samples there were no differences seen, but in the mid-sigmoid a significant difference was seen between the low butyrate and mid/high butyrate groups (p < 0.015). (C) Graph comparing butyrate concentration and the percentage of NRP-1 expression in the contralateral (white bars) and mid-sigmoid (filled bars) samples. NRP-1 expression was significantly higher in the low butyrate group in the mid-sigmoid compared to the field (p = 0.003), but no other differences between sample sites were seen.