Age-related melanogenesis in the eye of mice, studied by microautoradiography or 3H-methimazole, a specific marker of melanin synthesis

被引:24
作者
Lindquist, NG
Larsson, BS
Stjernschantz, J
Sjöquist, B
机构
[1] Uppsala Univ, Dept Pharmaceut Biosci, Div Toxicol, BMC, S-75124 Uppsala, Sweden
[2] Pharmacia & Upjohn Inc, Glaucoma Res Labs, S-75182 Uppsala, Sweden
关键词
autoradiography; eye; iris; melanin; melanocytes; melanogenesis; methimazole; pigment epithelium;
D O I
10.1006/exer.1998.0513
中图分类号
R77 [眼科学];
学科分类号
100212 ;
摘要
Whether melanogenesis occurs in adult eyes is still a matter of controversy. It has been widely held that the pigment epithelial cells are fully melanized at birth, and that the uveal melanocytes cease their melanin production in the very young individual. Therefore there should be no turnover of melanin in the adult eye. A number of studies have, however, demonstrated that the enzyme involved in melanin synthesis, tyrosinase, seems to be active also in the adult eye. The recent observation that a prostaglandin analogue, used in glaucoma therapy, caused increased iridal pigmentation in the treated eye, but not in the untreated eye, of adult monkeys and in humans, indicate that the adult eye at least has the capacity to produce melanin. In the present study (3)H-methimazole, a false melanin precursor, was administered to a series of DBA-mice, 3 weeks to one year of age. The eyes were removed 24 hr after a single i.p. injection of 3H-methimazole. Using microautoradiography the incorporation of radioactivity was studied in X-ray film covered sections comprising the entire eye. A very selective accumulation of radioactivity was seen in uveal melanocytes and in the pigment epithelial cells in the iris and the ciliary body. The level in the retinal pigment epithelium was low in the eyes of all ages. No uptake was seen in any non-pigmented ocular tissue. The most pronounced accumulation was seen in the pigment epithelium and melanocytes in the iris of the young mice, but some activity was seen in these cells also in the older mice. The presence of immature melanosomes seen in electron micrographs from iridal pigment cells and melanocytes of one year old mice indicate that new melanosomes are formed in these cells also in adult animals. The results of this study thus strongly indicate that there seems to be an active melanin synthesis in the adult eye of the mouse, most pronounced in iridal melanocytes and in the iridal pigment epithelium. (C) 1998 Academic Press.
引用
收藏
页码:259 / 264
页数:6
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