취장 및 간장에 미치는 식이성(食餌性) ethionine과 methionine의 독성(毒性)에 관한 연구
Studies on the toxicity of dietary ethionine and methionine to pancreas and liver
It has been demonstrated repeatedly that the administration of ethionine, a methionine analogue, will produce destruction of pancreatic tissue and liver cells.
Destruction of acinar cells of pancreas by the administration of excess methionine similar to that seen after feeding diets supplemented with ethionine was also reported but the liver was not involved by this amino acid. In an attempt to reproduce the results of these investigators the tissue damages were found to be slight and seen only irregulary in rats receiving ethionine on a complete diet and the result of tissue damages by excess methionine were also controversial.
The present studies describe the toxicity of dietary supplemented ethionine and methionine to liver and pancreas in rats fed a low protein diet.
Hundred five albino rats weighing around 120 gm were divided into three groups as follows;
1) Control group: A low protein diet containing 8% casein was fed throughout the experimental period.
2) Methionine group: A low protein diet(7% casein) supplemented with 1% methioine was used.
3) Ethionine group; A similar diet as methionine group except the supplementation of 1% ethionine instead of methionine was used.
Five animals per week from each group were killed for 6 weeks. The liver and pancreas were fixed in 10% formalin and histologic sections were prepared and stained with hematoxylin eosin. Serum amylase was expressed as much of glucose liberated from a starch substrate. The glucose was determined by the method of Nelson(1944). Serum glutamic pyruvic transaminase(SGPT) and glutamic oxaloacetic transaminase(SGOT) were determined by the technique described in Sigma Bulletin.
Summary and Conclusion
Toxicity of long term administration of ethionine or methionine to the liver and pancreas in rats on a low protein diet were studied weekly for 6 weeks and changes of serum enzymes and tissues are compared with control rats fed a low protein diet
1. Rats receiving ethionine on a low protein diet lost weight throughout the experimental period, however, animals receiving methionine on a similar diet gained weight.
2. The cumulative mortality of rats receiving ethionine on a low protein diet for 6 weeks was 33.3%, however, none of rats receiving methionine or a low protein diet alone was dead.
3. Inspite of the extensive destruction in pancreatic acini of rats receiving ethionine the serum amylase level was tend to continuously low. In methionine group serum amylase level was tend to elevate and pancreatic acine showed normal or a little hypertrophic features.
4. SGOT and SGPT levels were significantly elevated particularly at the second and third week in rats receiving ethionine, however, the enzyme level was not changed in methionine group.
5. Pancreatic and liver cell lesions in rats receiving ethionine were marked, particularly at the second week and no lesions ere found in rats receiving methionine throughout the experimental period.
6. Regeneration of pancreatic acini or liver cells were observed from the fifth week in receiving ethionine on a low protein diet.
By the above results it is to note that the toxicity of ethinoine to liver and pancreas were very striking on a low protein diet, however, no toxic effect was seen in rats receiving methionine on a low protein diet and it is felt that methionine supplementation rather prevents growth limitation and morphologic
changes caused by dietary low protein.