Fine structural demonstration of tyrosinase activity in the retinal pigment epithelium of normal and PTU-treated chick embryos.
The effect of phenylthiourea (PTU) on the retinal pigment epithelium of chick embryo was studied by using electron microscopy and electron-microscopic histochemistry. In the retinal pigment epithelium of PTU-treated, 10-day-old chick embryo, there is an abundance of premelanosomes and relative increases in the smooth endoplasmic reticulum (ER), and in the smooth-surfaced anastomosing tubular channels. Reaction products resulting from electron-microscopic histochemistry are first observed in some cisternae of the distal or active face of the Golgi apparatus and occasionally in small vesicles in the 5-day-old embryo, and these reactions become more intense with time. PTU treatment blocks melanin synthesis in the premelanosomes of 10-day-old chick embryo. Electron-microscopic histochemistry is completely inhibited by PTU treatment. Removal of PTU allows a weak positive reaction to histochemistry in some elements of the Golgi apparatus and in some small vesicles.
D000818:Animals; D004156:Catechol Oxidase / Q000502:physiology*; D002642:Chick Embryo; D006056:Golgi Apparatus / Q000648:ultrastructure; D006651:Histocytochemistry; D008543:Melanins / Q000096:biosynthesis; D014442:Monophenol Monooxygenase / Q000502:physiology*; D010670:Phenylthiourea / Q000494:pharmacology*; D010857:Pigment Epithelium of Eye / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure
D008543:Melanins; D010670:Phenylthiourea; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase