Yellow Phosphorus, one of the allotropic forms of elemental phosphorus, is highly
toxic to human being but yellow phosphorus-containing roach poisons and other
chemical substances are still available. When sufficient quantities have been ingested,
acute hemorrhagic inflammation of the esophagus and stomach is induced and followed
by fatty degeneration of the liver, kidneys, heart, and the voluntary muscles, but liver
damage is considered as the most significant one since cirrhosis or acute yellow atrophy
of the liver can occur and death may result from these causes (LaDue et al., 1944;
Goodman and Gilman, 1965; Harrison et al., 1966). The morphologic changes of the liver
induced by yellow phosphorus had been rather well established with light microscopic
studies and fatty degeneration and necrosis at the peripheries of lobules of the liver
have been accepted as a characteristic findings of phosphorus intoxication (Popper and
Schaffner, 1957; Robbins, 1967). The ultrastructural changes at the early stage of
intoxication, however, not fully established yet because previous studies on the
ultrastructural changes of the phosphorus-intoxicated rat liver are extremely variable in
result and not reproducible(J z quel, 1958; Ghoshal et at., 1969; Ganote and Otis, 1969).
The mechanism of fatty degeneration is still controversial. Recently, however, a very
interesting speculation was postulated by Choshal et al. (1969, 1971) explaining that
lipoperoxidation theory, which was very attractive in case of carbon tetrachloride
poisoning, was consistent with mechanism of yellow phosphorus intoxication in
morphological aspects.
The purpose of this paper is to describe the ultrastructural changes in the liver cells
of the yellow phosphorus intoxicated rat on the early stage and to discuss the
possibility of lipoperoxidation mechanism by studying the effect of DL-alpha-tocopherol,
a very powerful antioxidant.
Materials and Methods
Thirty two adult albino rats weighing around 200 gm. each were used regardless of
their sex. The animals were divided into three groups as follows:
Group Ⅰ: control animals
Group Ⅱ: yellow phosphorus treated animals
Group Ⅲ: vitamin E and phosphorus treated animals
Phosphorus was suspended in olive oil (0.5% mixture w/v) and administered into
peritoneal cavities in the amount of 0.75mg. per 100gm of body weight.
DL-alpha-tocopherol (Tofaxin, made by Wintrop-Steams Co.) was injected
intramuscularly in a dosage of 10 mg. per 100 gm. of body weight daily for 3 days
prior to yellow phosphorus treatment and at time of yellow phosphorus injection.
The control animals received olive oil only with the same volume with animafs of
group Ⅱ or Ⅲ. At intervals of 6, 12, 24 and 48 hours after the administration of yellow
phosphorus, the aninlals were killed. The liver and other organs were examined grossly
and the specimens for the light and electron microscopic examination were obtained
immediately from the liver.
Specimens for the light microscopic examinations were fixed in 10% neutral formalin
and embedded in paraffin. Sections of 6 micron thick were made and stained with
hematoxylin-eosin for studies of overall histologic change and periodic acid Schiff
reaction for glycogen. Frozen sections were also made and stained with oil red O for
demonstration of fat.
Specimens for the electron microscopic examinations were cut in 1 mm3
size and fixed in 6% glutaraldehyde in phosphate buffer pH 7.4 for 2 hours at 4℃ and
post fixation was followed in 1% osmium tetraoxide in phosphate buffer at pH 7, 4 for
2 hours. They were embedded in Epon 812 and cut into 400-500Å thickness with glass
knife. After staining with uranyl acetate and lead hydroxide, observation was made with
Hitachi model HU 11-E electron microscope.
Result and Discussion
In the liver of control rats, no stainable fat was demonstrated by oil red O method,
but in group Ⅱ, fatty metamorphosis was demonstrable at 6 hours after administration
of yellow phosphorus and involved almost the entire lobule except some hepatic
parenchymal cells adjacent to central vein. It advanced in degree through 12th hour and
reached its peak at 24th hour and maintained this until the 48th hour. Scattered
parenchymal cell necrosis and round cell infiltrations were also noted but did not reveal
any zonal character. In group Ⅲ, the fatty metamorphosis did not occur at the 6th hour
but at 12th hour mild changes were noted which also advanced with time. Vitamin E
failed to prevent inflammation and necrosis. PAS positive material was mildly decreased
in the liver throughout the experimental periods as compared with the control liver.
The most significant ultrastructural changes were found in rough endoplasmic
reticulum and were very distinctive. The rough endoplasmic reticulum was markedly
hyperplastic and arranged in parallel fashion occupying large areas of cytoplasmic
spaces. The studyed ribosome was intact and free ribosome was not increased.
Polysome formation, however, was not demonstrable. These changes were noted at the
6th hour and maintained these patterns until 24 hours after phosphorus injection but
markedly decreased in degree at 48th hour. The fat globules were identified at 6th hour
not in the cisternae but in cytoplasm and these findings were considered as evidences of
difference between carbon tetrachloride and yellow phosphorus intoxication.
In group Ⅲ, the same morphologic changes took place except the absence of fat
globule at 6th hour.
The smooth endoplasmic reticulum, lysosome, mitochondria, microbody, Golgi complex
and nucleus were not significantly altered in their morphologic characters in both groups
Ⅱ and Ⅲ.
In summary, the fatty changes induced by yellow phosphorus were not confined to
the periphery of the hepatic lobule but involved in almost the entire lobules even in the
early stage. The most significant and quite distinctive ultrastructural changes were early
hyperplasia of the rough endoplasmic reticulum and their parallel arrangement. Vitamin
E failed to prevent the toxic effect of yellow phosphorus completely and the
lipoperoxidation theory seems not to be convincing in cases of fellow Phosphorus
poisoning.
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