Metallothionein shows an age-related decrease in human macular retinal pigment epithelium.
OBJECTIVE
To investigate the possible role of zinc-metallothionein in human retinal pigment epithelium with regard to age-related changes.


METHODS
A cadmium/heme assay was used to quantitate metallothionein in isolated macular and peripheral retinal pigment epithelium from donors ranging in age from 28 to 91 yr (n = 16, mean age = 68.6 yr).


RESULTS
It was found that peripheral retinal pigment epithelium contained significantly more metallothionein and zinc than macular retinal pigment epithelium. Macular retinal pigment epithelium cells contained 17.6 +/- 2.2 micrograms metallothionein/mg cytosolic protein in donors younger than 70 yr, compared to 5.6 +/- 0.9 in macular retinal pigment epithelium from donors older than 70 yr, a 68% decline (P = 0.0007). In cultured retinal pigment epithelium, when we lowered the zinc concentration in the medium, metallothionein was reduced by 72% after 1 wk of incubation.


CONCLUSIONS
It is suggested that lower levels of metallothionein in retinal pigment epithelium are caused by reduced metallothionein gene activity or a faster rate of protein degradation, both of which are known to be regulated, at least partly, by bioavailable zinc.
Tate
D J
DJ
Sensory and Electrophysiology Research Unit, Touro Infirmary, New Orleans, LA 70115.
Newsome
D A
DA
Oliver
P D
PD
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D008266:Macula Lutea / Q000378:metabolism*; D008668:Metallothionein / Q000378:metabolism*; D008875:Middle Aged; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
D008668:Metallothionein; D015032:Zinc