Silicone Oil （Dimethylpolysiloxane）と神経障害—その一典型としてのSilicone Retinopathy発生病理

PATHOGENESIS OF NERVE TISSUE DAMAGE INDUCED BY POLYDIMETHYLSILOXANE:SILICONE RETINOPATHY AS AN EXAMPLE

緒言

　Silicone oilの毒性に関する記載は殆んど全面的にそのchemical inertnessを肯定するものに限られ^1），まして，発癌性高分子化合物としての認識は，本邦においても，米国と同様現実的な重みを欠くのが現状である。

　1970年，成毛^2）は，Silicone注入後一定の期間をへて発生した乳癌組織内に，明らかにSudanで濃染するSilicone-lipid-complexを記載，中性脂肪凝塊に埋没された腺組織中に注入されたSilicone oilの一部が，脂肪酸とcross linkageによってcomplexを形成しうることを暗示した。

(1) The biologic interaction of polydimethylsiloxane has long been speculated as having no con- troversial implication in terms of the chemical inertness. This is not true, particularly for nervous tissues under certain circumstances.

(2) Since silicone fluid in vitreous body creates an ideal oil-in-water dispersion at the vitreo-retinal interface, it is reasonable to assume that the principle of partition coefficients can be applied to the case.

(3) The first step of enzymatic lesions is a steep increase in alkaline phosphomonoesterase ac- companied with a rapid liberation of phospho- lipids. Lipids readily emulsify in alkaline mi- lieu, so that splitting by hydrolysis may be persistently accentuated.

(4) Disruption of mitochondria cristae due to acute swelling is also the initial and most striking phenomenon. Low-amplitude swelling potential of the neuronal mitochondria suggests that this may be irreversible.

This lesion perhaps occurs by exposure of double bonds of the unsaturated fatty acids to oxygen molecules and their subsequent autoxidation.

(5) Sticking-up of the hydrophilic polar group out of the silicone-phospholipid complex may pro- mote water swelling. Thus the intercellular space, which is comprised of an aqueous dif- fusion pathway, opens in a way that enables smaller particles of this complex to pass through it, and their water shells to coalesce.

(6) Equilibrium in silicone-lipid complex in an oil- in-water compariment at the vitreo-retinal in- terface may hardly be attained because of the ocular movement, although it is conceivable that a tentative stabilization would have main- tained between Cl and C2 compartments.

(7) Deprivation of the electron transport vehicle is of direct relevance to almost instantaneous depression of b-wave in ERG. Depression of ATP/ADP ratio under aerobic condition may exert a disastrous influence to already swollen- up mitochondria.