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Increase of Extravascular Albumin Pool and the Intracellular Accumulation of Vesicles in Transplanted Morris Hepatoma 9121¹

Biochemisches Institut [J. U., P. z., J. T., G. S.], Institut Biologie II [J. K.], and Pathologisches Institut [R. L.] der Universität Freiburg im Breisgau, Freiburg im Breisgau, Germany

Biosynthetically labeled albumin-³H from donor rats was injected into the femoral vein of 18 tumor-bearing rats. Blood samples, hepatomas (two per animal), and livers were removed at 10, 25, or 40 min after injection. Albumin, protein, and radioactivity were measured and albumin pool sizes were calculated. The values obtained for 10, 25, or 40 min after injection did not differ significantly. This demonstrates that the injected albumin-³H was distributed homogeneously in the blood stream throughout the body, including liver and hepatomas, and that no detectable change of the distribution of albumin between intravascular and extravascular compartments occurred during the experiment. The mean vascular albumin content of host liver was 2.1 ± 0.1 mg/g, wet weight, and that of Morris hepatoma 9121 was 1.4 ± 0.1 mg/g, wet weight. The mean extravascular albumin content of the hepatoma was considerably larger (3.5 ± 0.1 mg/g, wet weight) than that of host liver (1.0 ± 0.1 mg/g, wet weight). The ratio of extravascular albumin to total soluble protein was about 6 times larger in the hepatoma than in host liver. These values were independent of tumor size (weight range, 3.6 to 10.1 g).

Eighteen of the Morris hepatomas 9121 with weights ranging from 0.6 to 14.5 g were examined by light microscopy. The proportion of solid tumor tissue to tubular and necrotic areas decreased with increasing tumor weight.

The fine structure of the hepatoma cells differed from the appearance of a hepatocyte most conspicuously by the accumulation of clustered vesicles. Well-developed Golgi complexes with many associated secretory vesicles were more numerous than in liver parenchyma. The rough endoplasmic reticulum was less frequent than in liver and usually formed slender and isolated cisternae, characteristic of minimal-deviation hepatomas. Free polysomes appeared to predominate over bound ones. Microvilli-like structures were rare.

¹ This work was supported by grants from the Deutsche Forschungsgemcinschaft, Bad Godesberg, and the Stiftung Volkswagenwerk, Hannover, Germany.

² Miss Timko's work was supported by Fulbright grants, Bad Godesberg, Germany.

Received 10/20/71. Accepted 6/ 5/72.