Chondroitin sulfate proteoglycans are structural renewable constituents of the rabbit vitreous body.
OBJECTIVE
To characterize the vitreous intrinsic proteoglycans, investigate their dynamics, and examine their role in the supramolecular organization of the vitreous.


METHODS
Vitreous from normal rabbits was collected and processed for observation with the transmission electron microscope after treatment with glycosidases. Also, rabbits were injected intravitreally with [35S]-sodium sulfate and sacrificed at several time intervals after the injection. Proteoglycans (PGs) were assayed in the vitreous supernatant or in whole samples extracted with guanidine hydrochloride by polyacrylamide or agarose gel electrophoresis, followed respectively by fluorography or autoradiography, and ion-exchange chromatography and gel-filtration chromatography, combined with glycolytic treatment of the samples. The sulfated glycosaminoglycans (GAGs) were characterized by agarose gel electrophoresis after treating vitreous samples with protease and specific glycosidases.


RESULTS
The electron microscopic study revealed a network with hyaluronic acid (HA) as thin threads coating and connecting collagen fibrils. The elimination of the HA coat showed chondroitin sulfate granules (8-25 nm) arranged at regular intervals on the fibril surface. The chondroitinase ABC digestion, besides removing the granules, also caused the formation of thicker bundles of the collagen fibrils. The PG and GAG analysis indicated that there are three renewable PGs in the vitreous (e.g., one heparan- and two chondroitin-sulfate ones).


CONCLUSIONS
At least one of the chondroitin sulfate PGs is involved in the interactions that occur in the vitreous structure, mainly by providing adequate spacing between the collagen fibrils, a condition that is probably required for the transparency of the vitreous.
Góes
Rejane M
RM
Departamento de Biologia, UNESP, São José do Rio Preto, Brazil.
Nader
Helena B
HB
Porcionatto
Marimelia A
MA
Haddad
Antonio
A
Laicine
Eduardo M
EM
D000818:Animals; D011508:Chondroitin Sulfate Proteoglycans / Q000032:analysis* / Q000302:isolation & purification / Q000648:ultrastructure; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003094:Collagen / Q000032:analysis; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006026:Glycoside Hydrolases / Q000494:pharmacology; D019812:Heparan Sulfate Proteoglycans / Q000032:analysis / Q000302:isolation & purification; D006820:Hyaluronic Acid / Q000032:analysis; D008854:Microscopy, Electron; D011817:Rabbits; D014822:Vitreous Body / Q000737:chemistry* / Q000187:drug effects / Q000648:ultrastructure
D011508:Chondroitin Sulfate Proteoglycans; D019812:Heparan Sulfate Proteoglycans; D006820:Hyaluronic Acid; D003094:Collagen; D006026:Glycoside Hydrolases