Morphologic and cytochemical identification of microperoxisomes in human and non-human primate placental trophoblast.

Human and non-human primate placental villi (near term) were incubated in an alkaline 3,3' diaminobenzidine (DAB) medium to identify the distribution of microperoxisomes in these tissues. Catalase-positive microperoxisomes were present in small numbers in cytotrophoblast, but were virtually absent from syncytiotrophoblast. Microperoxisomes were roughly circular in shape and about 0.2-0.3 micrometer in diameter. They always had a close association with an element of agranular endoplasmic reticulum. The function of microperoxisomes in placenta, as in many other tissues, is uncertain. Whatever their function, they are presumably more important in cytotrophoblast metabolism than in syncytium.