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The effect of triton WR-1339 on the subcellular distribution of trypan blue and 125 I-labelled albumin in rat liver.

ABSTRACT: 1. The density-gradient distribution patterns of acid phosphatase, Trypan Blue and denatured (125)I-labelled albumin were studied by discontinuous sucrose- and isopycnic sucrose-density-gradient centrifugation on combined heavy and light mitochondrial (M+L) fractions of liver isolated from normal rats and from rats injected with Triton WR-1339. 2. The results obtained from the subfractionation of the M+L pellet of normal animals indicate that the equilibrium density of Trypan Blue and acid-insoluble radioactivity is the same as that for acid phosphatase, which suggests they are bound by a common membrane to form a distinct subcellular population of lysosomal nature. 3. In contrast, the analysis of the isopycnic gradients obtained on subfractionation of M+L pellets of liver isolated from rats treated with Triton WR-1339 show that the acid-insoluble radioactivity has an equilibrium density around 1.21, whereas the acid hydrolases, including cathepsin D, show the characteristic shift to an equilibrium density of around 1.12. Trypan Blue is distributed along the gradient with distinct peaks at densities 1.22 and 1.12. 4. Similar equilibrium-density distribution patterns were obtained with M+L pellets isolated from rats pretreated with Triton WR-1339 but not injected with Trypan Blue. 5. Treatment of the rats with Triton WR-1339 does not affect albumin digestion of isolated intact lysosomes despite the fact that most of the cathepsin D and the albumin ingested by phagocytosis are located in different vacuoles. 6. It is concluded from these experiments that in the liver of animals treated with Triton WR-1339 (125)I-labelled albumin is located within heterophagosomes which do not fuse with heterolysosomes containing the non-ionic detergent Triton WR-1339. The inability of these two lysosomal populations to fuse is not due to Trypan Blue.

SUBMITTER: Davies M

PROVIDER: S-EPMC1165924 | biostudies-other | 1973 Sep

REPOSITORIES: biostudies-other

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Project description:Selenium (Se)-deficient mice were labelled in vivo with single pulses of [75Se]selenite, and the intrahepatic distribution of the trace element was studied by subcellular fractionation. At 1 h after intraperitoneal injection of 3.3 or 10 micrograms of Se/kg body weight, 15% of the respective doses were found in the liver. Accumulation in the subcellular fractions followed the order: Golgi vesicular much greater than lysosomal greater than cytosolic = microsomal greater than mitochondrial, peroxisomal, nuclear and plasma-membrane fraction. At a dose of 3.3 micrograms/kg, more than 90% of the hepatic Se was protein-bound. When cross-contamination was accounted for, the following specific Se contents of the subcellular compartments were extrapolated: Golgi apparatus, 7.50 pmol/mg; cytosol, 0.90 pmol/mg; endoplasmic reticulum, 0.80 pmol/mg; mitochondria, 0.49 pmol/mg; nuclei, lysosomes, peroxisomes and plasma membrane, less than 0.4 pmol/mg. At 10 micrograms/kg, a roughly 2-3-fold increase in Se content of all fractions was found without major changes in the intrahepatic distribution pattern. An extraordinary rise in the cytosolic fraction was due to an apparently non-protein-bound Se pool. At 24 h after dosing, total hepatic Se had decreased to 6% of the initial dose and had become predominantly protein-bound. The 60% decrease in hepatic Se was reflected in a similar fall in the subcellular levels of the trace element. The Golgi apparatus still had the highest specific Se content, although accumulation was 5 times less than that after 1 h. The cytosolic pool accounted for 50% of the hepatic Se at both labelling times. After 1 h the Golgi apparatus was, with 19%, the second largest intrahepatic pool, followed by the endoplasmic reticulum with 16%. The high affinity and fast response of the Golgi apparatus to Se supplementation of deficient mice is interpreted in terms of a predominant function of this cell compartment in the processing and the export of Se-proteins from the liver.

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The effect of triton WR-1339 on the subcellular distribution of trypan blue and 125 I-labelled albumin in rat liver.

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