Rapid absorption following yolk delivery of labeled fatty acid. BODIPY-labeled fatty acid (BODIPY^® FL C₁₂), dissolved in canola oil (0.5–1.5 ng/nl), was injected into the yolk of zebrafish larvae. (A1–A3) Timecourse of fatty acid absorption. BODIPY^® FL C₁₂ (0.5 ng/nl) was injected into larvae at 3 dpf. The images shown are representative (n=4) and are taken from the same larva at different timepoints after injection (indicated in the top right-hand corner). Brightfield images in the top panels show the location of the canola oil drop (white arrow). The second panel shows combined brightfield and BODIPY^® FL C₁₂ fluorescence (green) images. (A1) At 5–10 minutes post-injection. (A2) At 3 hpi. Bottom panels reveal BODIPY-labeled fatty acid in the heart (arrowhead) and head vessels (left) and tail vasculature (right). (A3) At 24 hpi. Bottom panel reveals BODIPY^® FL C₁₂ in the yolk and newly formed intestinal lumen (arrowheads). (B) Labeled fatty acid enters the circulation. BODIPY^® FL C₁₂ (1.5 ng/nl) was injected into 1.5-dpf larvae and analyzed 2 hours later. BODIPY-labeled fatty acid fluorescence is shown merged with Nomarski microscopy to reveal larval anatomy. Images shown are representative (n=4). BODIPY-labeled fatty acids were distributed in the caudal artery and the caudal vein. (B1) ×20 magnification. (B2) ×40 magnification. Arrowheads point to red blood cells (RBC).

Mtp mediates BODIPY^® FL C₁₂ absorption. BODIPY^® FL C12 (1.5 ng/nl) was injected into the yolk of 1.5-dpf larvae obtained from adult mtp heterozygote (mtp^+/-) crosses. Following injection, larvae were incubated for 3 hours and then analyzed for vascular fluorescence. mtp mutants were identified phenotypically, as described previously (Avraham-Davidi et al., 2012). The images shown are representative for (A) wild-type and/or heterozygous siblings and (B) mtp-mutant larvae. Nomarski images are shown in the left panels. Fluorescent images (right panels) reveal that BODIPY^® FL C₁₂ was distributed in the tail vasculature of wild-type and mtp^+/- larvae (A), whereas mtp-mutant larvae (B) have negligible levels of vascular BODIPY-labeled fatty acid fluorescence. (C) Circulating BODIPY^® FL C₁₂ fluorescence was quantified (shown in the right-hand panel) in the caudal artery and veins (area 1). A background correction was performed using a non-vascularized region (area 2). Four experiments were performed using 21–24 larvae per experiment. Data are represented as the mean of means±the pooled s.e.m., ***P<0.00001, Student’s t-test.