A unique microvesicular sphere associated with the Golgi complex of gonadotrophs in the golden hamster.

A spherical accumulation of numerous, closely packed, minute vesicles, tentatively called a microvesicular sphere (MVS), was often found at the cis side of the Golgi complex in the gonadotroph of the hypophysis of the golden hamster. After prolonged impregnation with OsO4, the cis saccules of the Golgi stack and the MVS were stained with osmium. In gonadotrophs from normal and castrated hamsters, reaction products of thiamine pyrophosphatase (TPPase) and inosine diphosphatase (IDPase) were intensively localized in the trans and intermediate cisternae of the Golgi complex, respectively, but not in the MVS. Acid phosphatase (AcPase) reaction products were patchily distributed in the trans cisternae of the Golgi stack, but were not localized in the MVS in normal and castrated hamsters. However, in the blinded hamsters, in which gonadotrophs and their Golgi complexes were atrophic, AcPase reaction products were seen consistently in the MVS, and also in many of the Golgi cisternae in addition to those on the trans side. In such cells TPPase and IDPase activities were greatly decreased; the endoplasmic reticulum and Golgi complexes might be engaged in production of lysosomal proteins rather than secretory products. The MVS may represent an accumulation of special transfer vesicles between the endoplasmic reticulum and the Golgi complex, and may constitute an adjunct of the latter in certain cell types.