A radioautographic comparison of glycerol‐H3 and galactose‐H3 uptake during intestinal glyceride synthesis

Radioautography was used to compare the in vivo incorporation of glycerol‐H3 and galactose‐H3 in intestinal absorptive cells in relation to glyceride synthesis. Each labeled compound was injected, either singly or mixed with linoleic acid chyme, directly into ligated segments of rat upper jejunum. The segments were removed at 5 and 20 minutes and prepared for light and electron microscopic radioautography. Following glycerol‐H3 and chyme injections, label is rapidly incorporated in the vicinity of newly formed fat droplets in the apical endoplasmic reticulum. Later, labeled droplets accumulate in dilated Golgi cisternae and intercellular spaces. Galactose label is initially found in the Golgi region and later in the apical cytoplasm. Glycerol labeling is considerably reduced in the cells when the fat is extracted prior to radioautography, or when glycerol alone is absorbed. Galactose labeling is not affected by these procedures. The results indicate a significant incorporation of glvcerol label into newly synthesized glycerides, as previously also shown for glucose label. Galactose label follows a different metabolic pathway not related to glyceride synthesis.