Electron-Opaque, Lipid-Containing Bodies in Mouse Liver at Early Intervals After Partial Hepatectomy and Sham Operation

Insulin in the presence of high concentrations of glucose has a beneficial trophic effect on the development of primary cultures of hepatocytes. Compared to the situation observed in hormone-free control cultures, the flattening of the reaggregated hepatocytes is enhanced, and the reconstituted cell trabeculae are enlarged and tend to form a confluent monolayer after 3 days; the survival time is prolonged from 3 to 5 or 6 days. Ultrastructural modifications are also initiated by insulin; numerous glycogen particles appear, after 24 h, in between the cisternae of the proliferated smooth endoplasmic reticulum. After 48 h, large amounts of glycogen are stored, and numerous polysomes are present. A small number of cells show an increased synthesis of lipid droplets in the lumen of the smooth endoplasmic reticulum and form liposomes at the same time. After 72 h, cytolysomes filled with glycogen develop, simulating glycogenosis type II. Simultaneously, microtubules and microfilaments, closely related to numerous polysomes, appear in cytoplasmic extensions constituting undulating membranes.The biochemical data demonstrate that, in the absence of insulin, a high concentration of glucose stimulates glycogenesis and hinders glycogenolysis. This effect of glucose on polysaccharide synthesis is progressively lost. The addition of insulin to the cultures induces, after 48 and 72 h, a three-to fivefold increase of the glucose incorporation into glycogen, as compared to the controls. The presence of insulin is required to maintain the hepatocyte's capacity to store glycogen. Glycogen synthetase is converted into its active form under the influence of glucose. Insulin increases the rate of activation.Primary cultures of hepatocytes isolated from adult rats were used to study the effect of insulin on various metabolic pathways in the liver. As stated by Krahl (48), the primordial function of insulin consists of promoting the formation and storage of macromolecules such as glycogen, lipids, and proteins. Particular efforts were devoted to the study of the effects of insulin on glycogenesis, but contradictory results on the rapid effect of the hormone were obtained during in vivo (6,10,22,24) and in vitro investigations (35,55,64,65). In isolated hepatocytes, the early stimulation of glycogen synthetase and of the synthesis of polysaccharide by insulin has not been demon-

Section: Lipid Accumulationsupporting

confidence: 67%

Effect of insulin on ultrastructure and glycogenesis in primary cultures of adult rat hepatocytes

Bernaert¹,

Wanson²,

Drochmans³

et al. 1977

“…15), or (2) particles, of varying electron opacity, 40-200 m/~ in diameter, surrounded by well demonstrable membranes. Structures similar to the latter have been called granules (9), droplets (36), bodies (43), masses (22), or liposomes (10). The term "particle" has been chosen in order to differentiate these bodies from the lipid droplets, defined above.…”

Section: Fate Of Label During Specimen Preparationmentioning

confidence: 99%

Lipid Synthesis, Intracellular Transport, Storage, and Secretion

Stein

1967

257

A time sequence study of intracellular movement of labeled lipid in the liver was carried out on fasted and ethanol-treated rats injected with either palmitate-3H or glycerol-3H by electron microscopic radioautography. The elimination of water-soluble lipid precursors during specimen preparation was checked and found to be complete. The labeled lipid product in the tissue was identified as mostly triglyceride. A dehydration procedure was adapted to minimize the loss of lipid during specimen preparation. At 2 min after injection, the earliest time interval studied, both precursors were found to have penetrated the liver cells, and the label was found over both rough and smooth elements of the endoplasmic reticulum, which is the site of glyceride esterification. From 5 min on, in fasted and especially in ethanol-treated rats, the label was seen also over lipid droplets 0.5-2.0 # in diameter, which represent "storage lipid" (slowly turning over compartment). Mitochondria became labeled mostly at later time intervals after injection. From 10 rain on, concentration of label was seen over the Golgi apparatus, containing small osmiophilic particles. Association of label with groups of particles in smooth-surfaced vesicles and vacuoles in and near the Golgi apparatus and in the vicinity of the sinusoidal border was seen, both after palmitate-SH and glycerol-SH. It is proposed that these particles represent lipoproteins which are formed in the endoplasmic reficulum, "processed" in the Golgi apparatus, and transported in vacuoles to the sinusoid surface to be discharged into the circulation.

“…Many electron-opaque bodies may be observed in regenerating mouse liver after partial hepatectomy. These bodies occur in both intracellular and extracellular locations and are thought to contain some lipid component (1,2). In the present study two sets of experimental conditions known to affect lipid metabolism have been established in order to obtain more information concerning the electron-opaque bodies.…”

Section: Introductionmentioning

confidence: 99%

Electron-Opaque Bodies and Fat Droplets in Mouse Liver After Fasting or Glucose Injection

Trotter

1967

Self Cite

Fasting produces an increased mobilization of lipid from adipose tissue to the liver and a decreased hepatic lipogenesis, but the administration of glucose stimulates lipid synthesis by the liver. After fasting of C3H mice numerous electron-opaque bodies and large lipid droplets were present in the liver. In the liver of untreated controls only a few small electronopaque bodies and an occasional fat droplet were observed. After glucose injection the number of electron-opaque bodies in the liver was no greater than that observed in livers of saline-injected controls. In the livers of all groups these bodies were located intracellularly within cytoplasmic vesicles; those in extracellular locations were not membrane bounded and were located at indented and thickened hepatocyte plasma membranes or within the space of Disse. In fasted liver the dense bodies were often associated with large fat droplets.