L-Asparaginase가 백서간에 미치는 영향

Abstract

[한글]

[영문]Introduction

In 1953, Kidd reported that the administration of guinea pig serum caused the regression of certain mouse and rat lymphomas. Later, Broome(1961), Old et al.(1963), Boyse et al,(1963), Capizzi(1969), Leventhal(1970) and Ohno(1970) demonstrated that this tumor inhibition was due to the L-asparaginase content of

guinea pig serum. The discovery by Mashburn and Wriston(1964) that the L-asparaginase as present in escherichia coli had tumor inhibiting properties made it possible to obtain a purified enzyme for evaluating antitumor activity in man.

Hill(1968) suggested that it might be a promising agent for the treatment of acute leukemias and that its action was accompained by a minimum of toxic side effects.

The side effects encountered were chills, fever, hypersensitivity reaction, changes in liver function, pancreatitis, and central nervous system dysfunction by

Zubrod(1970), Shaw et al.(1970), Bettigolo(1970) and Heskell(1969).

Hepatic toxicity was observed more frequently than toxicity to other organs. But the pathogenesis of the toxic effects on the liver is presently unknown.

The purpose of the present investigation s to determine toxicity and ultrastructural alterations of rat liver cells following the administration of different dosis of L-asparaginase.

Materials and Methods

Rats weighing about 180∼200gm were used for the experiment. L-asparaginase was the product of Merk Sharp and Dohme Research Laboratories, L-asparaginase was dissolved immediately before used in saline solution.

Experimental Schedule

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Group Dose No. of animals

----------------------------------------------------------------- Group-1 0.5cc NaCl 21

Group-2 L-asp. 2,000IU/kg with 0.5cc NaCl 21

Group-3 L-asp. 6,000IU/kg with 0.5cc NaCl 21

Group-4 L-asp. 20,000IU/kg with 0.5cc NaCl 21

----------------------------------------------------------------- Animals were sacrified at 3 hours, 6 hours, 18 hours, 24 hours, 48 hours, 72 hours and 5 days after a single subcutaneous injection of L-asparaginase. White blood cell count, and determination of serum total protein, albumin and alkaline phosphatase were made. The WBC count was done by a modification of the method described by Conway(1958). Total protein and serum albumin were measured by a method of Mallowy(1937) and Durum technique. Alkaline phosphatase was measured by the method of Bower and Mc Comb(1966) and expressed in Bodansky units.

The tissues of the liver, Kidney, pancreas and lymph nodes were fixed in neutral formalin and sections were prepared by standard paraffin embedding procedure and stained routinely with Hematoxylin and Eosin, and sections of the liver were also

stained by Methyl-green pyronin and Oil red-O for light microscopy.

Electron Microscopy specimens of the liver were taken from the median lobe and fixed for 2 hours 40℃ in one percent osmium tetraoxide in veronal buffer with pH7.4(Palade, 1952). All tissues were dehydrated in graded alcohol and embedded in Epon 812 according to standard procedures.

Thin sections were cut with LKB Ultratome, then stained with uranyl acetate and lead citrate, and observed with the Hitachi HU 11-E Electron Microscope.

Results and Disscusions

WBC count dropped in all L-asparaginase treated groups, and gradually returned to normal value around 5th days. Abnormalities on liver function was indicated by a slightly decreased serum albumin. The histological changes were most notable in the

liver, whereas changes in other organs were insignificant. Pyronophilic materials

decreased markedly around the nuclei of liver cells of L-asparaginase in 6 hours and 18 hours after the injection of L-asparaginase in group 3 and 4. The ultrastructural alterations consisted of disorganization, dilation of rough endoplasmic reticulum and detachment of ribosome from 3 hours till 18 hours in all animals treated with L-asparaginase.

Six hours after injection the nucleolar change consisted of slight segregation of small amounts of granular and fibrillar elements.

In summary, the data obtained by the present study indicate that the administration of various doses of L-asparaginase bring about an inhibition of protein synthesis of the liver cells as evidenced by reduction of pyronophilia, dilatation of rough endoplasmic reticulum, and detachment of ribosome and this

effect leads to accumulation of lipids in the liver cells.