Ethionine 투여가 흰쥐 피부의 인지질대사(燐脂質代謝)에 미치는 영향

Abstract

[한글]

[영문]

It is evident that all cells have membranes - for the cell membrane proper, the mitochondria, the nucleus, the Golgi apparatus, the endoplasmic reticulum, and/or whatever other organelles are present - the epidermis, a highly cellular tissue,

must have phospholipid for its membranes. Insight as to how these phospholipids might function in these membranes should progressively increase as our knowledge of the composition of the lipids increases. Furthermore, it is necessary to investigate the metabolism of phospholipids in skin.

Farber and his associates (1950, 1951, 1958) reported that ethionine, an ethyl analogic of methionine, induced a fatty liver in female but not in male rats and also inhibited protein synthesis in the liver of rats. Farber interpreted that the sex difference in the effects of ethionine upon hepatic protein metabolism is mediated by androgens.

Shull (1962) has proposed a concept that the administration of ethionine markedly decreased the level of ATP as well as that of phosphorylase in the liver and also inhibited liver ribonucleic acid synthesis

Recently, Schluck (1968) et al. concluded that the low levels of plasma triglycerides observed in ethionine·treated rats after feeding corn oil are not a reflection of decreased fat absorption but result mainly from the developing fatty liver which traps chylomicron triglycerides and fails to release them back into the

systemic circulation.

According to these results, it is established that an accumulation of liver lipid and inhibition of protein biosynthesis were occured in response to ethionine administration.

It was also found that ethionine can produce profound alteration in the uptake of 32P into individual liver phospholipids (Ulsamer and Glenn, 1966).

Recently, many investigators demonstrated the metabolic activities of carbohydrates, fats and proteins in the human and animal skin (Brooks et al: 1959, Cruickskank: 1954, 1956, 1958, 1962, Freinkel; 1959, 1960, Gilbert; 1962, Triesemer: 1954, Mier; 1966, 1969, Yardley: 1963, Hsia; 1966, Lipkin; 1965,

Nicolaides: 1955, Wheatley; 1967, Rotkberg; 1964, Fukuyama and Epstein; 1968).

On the basis of animal experiments, Yardley and Godfrey (1963) postulated talc possibility that the administration of substrates might product marked alteration in 32P incorporation into the skin phospholipids.

However, it is not eluoidated whether and to what extent alteration in the phospholipid metabolism is influenced by ethionine in the skin.

For this reason, a comparative study was undertaken on talc incorporation of 32P·orthophospbate into skin and hepatic phospholipids in female rats treated with ethionine.

Materials and Methods

Treatment of animals: Female .rats weighing about 150∼200gm were fed ad libidum.

Rats were fasted of food for 24hours and then injected intraperitoneally with 3 divided doses of 2% DL·ethioninc in saline (100mg/100gm body weight) at one hour intervals.

In vivo experiments: Rats were injected intraperitoneally wish 1mCi/200gm body weight of 32P-orthophosphate 24 hours after the first injection of ethionine or saline and sacrifice 2, 6 and 24hours after 32P injection. 1,000mg of liver or skin were homogenized with 9 vol. of methanol, and then extracted with chloroform according to the procedure of Folch et at.

In vivo experiments: 1,000mg of skin from rat treated with saline and ethinone above, was sliced into small pieces and incubated with 10 ml. of Krebs-Ringer-bicarbonate solution(CaCl^^2 omitted) containing 0.1% glucose, streptomycin (50μg/ml) and 50 μCi of 32P-orthophosphate per ml. of medium under the air phase at 37℃ for 6 hours. Lipids were extracted as described above.

Lipid analysis

Phospholipids from each group wcrc separated by thin-layer chromatography using the solvent system chloroform-methanol-water (65:26:4, v/v) described by Skipski et al.

Phospholipid bands were visualized under ultraviolet light after being sprayed wish ninhydrin, Dragendorff's reagent and iodine vapor.

Measurement of radioactivity

Phospholipid areas on the thin-layer chromatogram were scraped into counting vitals containing a mixture of 0.4% 2.5-diphenyloxazole and 0.01% 1,4-bis 2-(5-Phenyloxazolyl) benzene in toluene and were counted with a liquid scintillation counter or extracted with chloroform-methanol mixture (2:1, v/v), transfered to planchet and counted with gas flow counter.

Results and Summary

The effects of ethionine on the incorporation of the 32P-orthophosphate into skin phospholipids are followings.

1. The administration of ethionine to rats exhibited no great differences in the concentration of phosphatidylcholine and phosphatifylserinc, however, contents of lysophosphatidylcholine and phosp-hatidyletbanolamine in the skin differed significantly between control and ethionine-treated rats.

2. Rats administered ethionine incorporated a relative lower proportion of the radioactivity into the skin than that of the liver. Such a response seen in rat skin can be observed throughout present experiments. In vivo incorporation studies

with skin from ethionine·treated rats showed that ethionine lowered the 32P incorporation into phosphatidylcholine and pbosphatidyletbanolamine. However, radioactivity of phosphatidylethanolamine counted only 7∼25% when compared with

that of phosphatidylcholine.

3. Incorporation in vitro of 32P into phosphatidylcboline elevated markedly and less into phosphatidylethanolamine of ethionine treated slice than slices from control rats.

4. The rat skin phospholipid fractions, i.e., phosphatidylcholine, lysophosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, sphingomyelin and phosphatidylserine have been shown to be actively incorporated by

37P·orthophosphate.

5. The present study have demonstrated the operation of Kennedy pathway of phospholipid metabolism in rat skin.