ULTRASTRUCTURAL LOCALIZATION OF A CHARACTERISTIC ACID PHOSPHATASE IN GRANULES OF RABBIT BASOPHILS

Abstract

Bone marrow basophils incubated in Gomori medium at pH 6.0-6.8 exhibited strong acid phosphatase activity suggestive of a potential role in endocytosis in one-third of the cytoplasmic granules and also in Golgi elements. Buffy coat basophils contained about one-third as many reactive granules. Reaction product was confined to the threadlike component of the larger granules predominant in early basophils and was absent from the denser-type granules predominant in late basophils. In centrioles of basophils acid phosphatase appeared localized between triplet fibers. Reactivity with the Gomori medium was diminished at pH 5.0, absent at pH 8.0 and only slightly decreased with p-nitrophenyl phosphate as substrate. Basophils incubated in Barka-Anderson medium at pH 5.0-6.8 revealed light acid phosphatase activity in the Golgi lamellae but essentially none in cytoplasmic granules. Tris-maleate buffer of the Barka-Anderson medium replacing the sodium acetate of the Gomori medium inhibited the reactivity in the granules. Incubation in media containing NaF, or lacking substrate, eliminated the heavy precipitates in granules and Golgi elements but yielded light, nonenzymatic lead staining in Golgi and tubulovesicular structures and atypical granules present only in buffy coat basophils.