La Struttura Delle Proteine Epatiche in Corso Di Cancerogenesi Da P-Dimetilaminoazobenzene: Osservazioni Viscosimetriche e Denaturazione Da Urea

The viscosimetric behaviour of three protein fractions from liver has been studied in 4 groups of rats (normal rats, rats fed Cantero diet alone, Cantero diet + DAB, rats bearing developed hepatoma). The treated rats were sacrificed at different times from the beginning of treatment. The protein fractions were obtained from 3 subsequent extractions from liver and from hepatoma:

1) 0,9 per cent NaCl solution buffered with phosphates (pH 7).

2) 10 per cent NaCl solution (pH 6,25).

3) 0,2 per cent NaOH solution (pH 12).

The starting point of these researches is to be looked for in the conception supported by Rondoni that the cell cancerization does not represent a chemical modification at the atomic level but rather an architectural modification of protoplasmatic macromolecules, of their configuration and of intermolecular relation at supermolecular and ultrastructural level.

The following conclusions may be drawn:

I) A decrease of total N content has been observed in the liver during hepatomas formation. Some hypothesis on this subject are advanced, basing upon N distribution in the three groups of the examined proteins.

II) In the four animal groups no significant viscosimetric differences have been observed in the protein extracts in saline solution and in NaCl.

III) A significant increase in viscosity has been observed for the nucleoprotein fraction extracted by sodium hydrate: such increase is progressive in the treated animals and reaches the highest value in those bearing hepatomas. The altered viscosity is likely ascribable to a structural alteration of some protein or nucleoprotein macromolecules (denaturation or polymerization) of liver cells during carcinogenesis.

IV) The viscosimetric determinations have been repeated after denaturation of the protein solution by urea: concordant results have been observed in the 4 groups of animals as concerns the obtained fractions.

After treatment, the viscosimetric behaviour confirms the presence of globular proteins in the first fraction and filamentous proteins in the second one. In the third fraction, proteins having globular behaviour are observed, likely due to the splitting of the filamentous structure brought about by sodium hydrate.