Intestinal Triglyceride Absorption in the Rat

Abstract

This report provides information on the morphology of fat absorption in rat intestinal epithelial cells. Three types of experiments were performed: (a) intubation of corn oil into fasted rats, (b) injection of physiological fatty-chyme prepared from fat-fed donor rats into ligated segments of jejunum of fasted animals, and (c) administration of electron-opaque particles in corn oil and markers given concurrently with the fat. These results support the hypothesis that fat is absorbed by selective diffusion of monoglycerides and fatty acids from micelles rather than by pinocytosis of unhydrolized triglycerides. Evidence is presented that the pits between the microvilli, previously believed to function in the transport of fat, are not involved in this process. Instead they appear to contribute their contents to lysosomes in the apical cytoplasm. Arguments are offered that the monoglycerides and fatty acids diffuse from the micelle while the latter is associated with the microvillous membrane of the absorptive cell. These micellar components penetrate the plasma membrane and diffuse into the cytoplasmic matrix where they encounter the SER. Triglyceride synthesis occurs in the SER and results in the deposition of fat droplets within its lumina. The synthesis of triglycerides and their sequestration into the SER establishes an inward diffusion gradient of monoglycerides and fatty acids.

Intestinal Transport of Antibodies in the Newborn Rat

“…2) . The vesicles stain less densely but otherwise appear similar to the apical lysosomes described in cells of the adult intestine (Cardell et al ., 1967) . The second type of vesicle consists of infrequent small vacuoles mostly free of visible contents (Fig.…”

“…The fact that the only ferritin tracer found within these cells was present within the small dense lysosomal bodies suggests that any material that does enter these cells is degraded rather than transported to the circula-2 0 8 J tion . This small amount of tracer seen in the dense bodies probably reflects a nonselective uptake similar to the uptake observed in cells of the adult (Cardell et al, 1967 ;Casley-Smith, 1967 ;Cornell et al ., 1971) . Quantitative estimates (Warshaw et al ., 1971 ;Walker et al ., 1972) indicate that transport of intact protein to the circulation is extremely small in the adult compared to the amount of antibody transport in the neonate (Halliday, 1955 b ;Rodewald, 1970) .…”

“…2, 4) . Coated vesicles do not seem to make contact with other organelles and, in particular, Golgi saccules, though such contacts have been reported for jejunal cells of the adult (Cardell et al ., 1967) . Two other vesicle types are noteworthy in the apical cytoplasm.…”

A Morphological Study of the Replication of Breda Virus (Proposed Family Toroviridae) in Bovine Intestinal Cells

“…3 are leaving the cell and not entering it. However, the plasma membrane of normal intestinal cells is highly polarized, and while both uptake and release via coated vesicles may occur at the apical membrane, only release has been described to occur at the basolateral membrane (Cardell et al, 1967;Steinman et al, 1983).…”

Intestinal absorption of triglycerols

“…According to Paris andClement (1965, 1969) Some studies using autoradiography with electron microscopy (Strauss and Ito, 1965 ;Cardell, Badenhausen and Porter, 1967 ;Dermer, 1968 ;Carlier, C[6ment and Noirot-Thimothée, 1969 ;Carlier, 1971Carlier, , 1973 have made it possible to determine lipids at some levels (microvilli, subjacent apical cytoplasm) where they could never have been detected by staining ( fig. 6A).…”