TRPV1 mRNA expression was observed in rat INS-1, RINm5F cells [54], and INS-1E cells [58], and immunostaining displayed TRPV1 expression in INS-1E cells [55], rat islet endocrine cells [54], but not in β-cells from ZDF rats [45], NOD mice [50], or from isolated human islets or insulinomas [55]. This evidence concerns the gene TRPV1 and pancreatic insulinoma.