Methotrexate가 白鼠胃腸管粘膜에 미치는 影響

Abstract

[한글]

[영문]

Since the report of aminopterine --folic acid antagonists -as a chemotherapeutic agent for the remissions in acute leukemia in chidren by Farber et al. (1948), investigators (Burchenal et al., 1951; Schoenbach et al., 1952; Li et al,, 1960) have proven folic acid antagonists to be of definitely effective although limited

value in the treatment of a variety of malignancies as well as in benign hyperplastic skin disorders (Gubner, 1951; van Scott et al., 1964).

The anticancerous activity of the folic acid antagonists is based on inhibition of mitoses by interference of synthesis with deoxyribonucleic acid (DNA) and ribonucleic aoid (RNA) (Werkheizer, 1963). This inhibitory activity of cellular

proliferation, however, is a non-specific one, and affects not only cancer cells, but also any rapidly growing normal cells which cause cellular injuries and a variety of side effects. The important toxic effects of methotrexate includes injuries to the hematopoietics(Phillips et al., 1950; Elison, 1957; Lipsett, 1963; Heiderberger and Anshfield, 1963), and to the gastrointestinal tract (Taylor et al., 1950; Dacie et al., 1951 ; Condit, 1960).

Clinical use of this agent is frequently limited by its toxic effects on the gastrointestinal tract, the most important of which are nausea, vomiting, diarrhea and stomatitis. It is now generally appreciated that the rate of cell turnover in the intestinal epithelium is extremely rapid (Leblond and Stevens, 1948; Leblond and Messier, 1958; Quastler and Sherman,1959). Associated with this rapid turnover is a very high degree of mitotic activity. Therefore, it seems likely that the folic acid antagonists, which probably exert their therapeutic effect by mitotic inhibition, produce severe gastrointestinal disturbances by interfering with the replacement of the digestive epithelium. The gastrointestinal tract thus provides an interesting model in which to study the effects of the folic acid antagonists.

A few reports of the studies, concerning the effects of methotrexate on the intestinal mucosa have dealt mainly with the alterations by administration of a single doss of methotrexate but no attention has been paid to the effect of repeated administrations of methotrexate. Therefore, to study and characterize the histopathologic alterations in the gastrointestinal tract after repeated administrations of methotrexate seems appropriate and important. At the same time,

the morphologic changes are precisely studied at regular intervals, 1 day, 5 days, 10 days and 20 days after cessation of methotrexate.

Materials and Methods

Healthy albino rats weighing around 200 grams were used. A total of survived 55 rats were subjected to the experiment. The animals were divided into 5 major groups and treated as follows.

Group Ⅰ; Methotrexate administration for 1 course (19 rats)

A. 1 day after cessation

B. 5 days after cessation

C. 10 days after cessation

D. 20 days after cessation

Group Ⅱ; Methotrexate administration for 2 courses (19 rats)

A. 1 day after cessation

B. 5 days after cessation

C. 10 days after cessation

Group Ⅲ; Methotrexate administration for 3 course7(5 rats)

A. 1 day after cessation

Group Ⅳ: Methotrekate administration for 4 courses (5 rats)

Group Ⅴ: Normal entreated controls (7 rats)

Methotrexate was given orally in a dose of 0.5 mg. per kg of body weight daily for 5 consecutive days for 1 course, and second, third and fourth courses of 5 days with 0.4 mg. per kg of body weight daily were given intraperitoneally 10 days after

the end of the previous courses.

During the experimental period, body weight was measured at intervals of 5 days.

Surving animals were sacrificed at the end of the experimental period. At autopsy, the organs particularly gastrointestinal tracts were grossly examined and histological examinations of gastrointestinal tract, bone marrow, spleen and liver were made.

Tissues for histologic examinations were fixed in 4% neutral formalin, and cut in 6 micron thickness after paraffin embedding, and stained with routine hematoxylin-eosin, periodic acid Schiff(PAS) for mucin, Feulgen for deoxyribonucleic acid (DNA), methyl green pyronin for ribonucleic acid (RNA), and trichrome for connective tissue.

Result and Summary

The body weight in untreated normal controls gradually increased, but in the methotrexate administered groups the body weight remained stationary.

Gross examination of the gastrointestinal tract presented no significant changes, and also microscopic examination with low magnification showed no remarkable changes, but with high magnification a variety of significant and interesting changes were identified.

Histopathologic changes of the gastrointestinal tract were marked in the small intestine, lesser in the large intestine, and mildest in the stomach. Those histologic changes consisted of atrophic and hypoplastic glands with occasional cystic dilatation and loss of goblet cells, decreased mitoses, decreased DNA and

RNA contents, and also decreased mucus secretion. Infiltration of inflammatory cells was also noted in the stroma.

In the small intestine, Group I-A, one day ofter cessation of one course, showed atrophic and hypoplastic changes of the glands and surface epithelium with loss of goblet cells. Mitoses were makedly decreased in the surface epithelium and Crypts of Lieberkohn. PAS stain showed markedly reduced mucus secretion, and also DNA and RNA contents were significantly reduced. Hyperemia and infiltration of inflammatory cells in the stroma were also noted. But these changes gradually returned to normal

from the 10th day after cessation. In Group A of Group Ⅱ, Ⅲ, and Ⅳ, those histologic changes were accentuated and occasionally cystic dilatation of the atrophic glands was also noted. However, the changes gradually returned to normal as in Group Ⅰ.

The spleen showed hyperplasia of lymphoid follicles on the 10th to 20th day after cessation of the administration. Extramedullary hematopoiesis were marked on the 10th day and reticulum cell hyperplasia marked on the 20th day after cessation.

The bone marrow showed marked hypoplasia with congestion and even hemorrhage immediately after the cessation. This was more accentuated in Group Ⅱ, Ⅲ, and Ⅳ, but it returned promptly to normal or even hyperplastic state by the 10th day after cessation.

The changes in the liver consisted of a mild degree of cloudy swelling, focal necrosis, and a moderate degree of fatty metamorphosis. A liver on the 20th day after cessation in Group Ⅰ disclosed a moderate degree of liver cirrhosis.

In summary, administration of methotrexate induced a variety of morphological changes in the mucosa of the gastrointestinal tract, most marked in the small intestine, leaser in the large intestine, and least in the stomach. And repeated administerations accentuated the morphological changes, but these histologic alterations promptly or gradually returned to normal by the 20th day after cessation of the administration.