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Peroxisomes in pigment epithelium and Müller cells of amphibian retina possess D-amino acid oxidase as well as catalase.
Beard ME
,
Davies T
,
Holloway M
,
Holtzman E
.
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In this paper we identify peroxisomes in Müller cells and retinal pigment epithelial cells of Rana pipiens and Xenopus laevis by virtue of their content of cytochemically stainable catalase. These organelles have the form of an extensive, branched system of tubules in the retinal pigment epithelium and appear as discrete ovoid structures in the Müller cells. In both the pigment epithelium and the Müller cells a second peroxisomal enzyme, D-amino acid oxidase, can be detected in the same structures as catalase by means of a cerium-based cytochemical staining procedure. This oxidase is active only against nonpolar and polar, uncharged D-amino acids.
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2905671
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FIG. 1. In retinal pigment epithelial cells of Rana, catalase-reactive peroxisomes (arrows) appear as
elongate sacs or tubules as well as more dilated or discrete profiles. The peroxisomes frequently lie
adjacent to the myeloid bodies (mb; see also Fig. 3). x 4300C. Here and in all following figures the bar
represents = 0.1 pm.
FIG. 2. Cat&se-reactive bodies in Kuw retinal pigment epithelium often appear as clustered profiles
(arrowheads, a) as would be expected for sections through a branched. interconnected network (arrows.
a, b). Large granules (g). either pigment or lysosomes. may also stain (see Discussion) (a) x43000:
(b) x75000.
Fro. 3. Cerium reaction product indicative of n-amino acid oxidase activity is deposited in the
peroxisomes (arrows) of retinal pigment epithelial cells of Rana (cf. Figs 1 and 2). The large granules (g)
stein variably and nonspecifically (see Discussion). (a) u-Valine as substrate: (b) D-proline as substrate.
(a) x 75000: (b) xGOOOO.
FIG. 4. Peroxisomes (arrows) show no cerium deposits when o-amino acid oxidase is inhibited by kojic
acid (a)\ and little or no staining when aminotriazole is omitted from the medium (b). Peroxisomes arc
difficult to identif? definitively in such preparations because, in the absence of reaction product. they
show no clearly distinctive morphology. (a) x 33000: (b) x 45000.
FIG.
FIG. 5. Miiller cells show elongate to ovoid peroxisomes (arrows) stained for cat&se (a) and for
D-amino acid oxidase with proline as substrate (b). The disruption of the tissue in (b) is due to the use
of Triton to permeabilize the preparation in the cerium procedure. (a) x 45000; (b) x 35000.
