Refeeding mice (RF) after a 6-h daytime fast (FD) increase oleic acid levels in duodenum (Duod.) and jejunum (Jej.) of wild-type (A), but not CD36-null mice (B). (C-E) duodenal infusion of the unnatural oleic acid analog 10Z-heptadecenoic acid (HAD) increases jejunal levels of (C) HDA, (D) heptadecenoylethanolamide (HDE), and (E) 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphoethanolamine-N-heptadecenoyl (NAPE), open bars, Vehicle (50 mM Tris buffer); closed bars, HAD infusion. Infusions were conducted at 0.5 ml/min for 10 min and jejunal tissue was harvested 30 min after starting the infusion. (F,G) Oral gavage of HDA (200 mg/kg in 1 ml of saline/polyethylene glycol/Tween 80, 90/5/5, vol/vol; closed bars) increases jejunal levels of HDA (F) and HDE (G) in wild-type (+/+), but not in CD36-null (-/-) mice, open bars, Vehicle (saline/polyethylene glycol/Tween 80, 90/5/5, vol/vol). One asterisk, p < 0.05; two asterisks, p < 0.01; three asterisks, p < 0.001; n = 5-6 per group.