BLASTS’

A single injection of puromycin was given to rats in a dose sufficient to produce almost total inhibition of protein synthesis in pancreas and liver. By 10 mm after injection, Golgi saccules in pancreatic acinar cells, hepatocytes and ameloblasts appeared grossly and irregularly distended, and almost devoid of content. In pancreas the condensing vacuoles near the inner face of the Golgi were often altered, and those normally present in ameboblasts were lacking. Between 2 and 3 hr after injection, protein synthesis had started anew. At this time, granules without limiting membranes appeared within cis-ternae of the rough endoplasmic reticulum in acinar cells and ameboblasts. These intra-cisternal granules are believed to consist of newly synthesized secretory protein which could not be transported through the disrupted Golgi apparatus to be packaged into secretory granules. Indeed, by 3 hr postinjection the secretory granules which normally abound in the apical processes of ameloblasts were sparce or absent. Thus, while bio-chemical evidence indicates that puromycin blocks protein synthesis on the ribosomes, the use of this antibiotic in vivo results in alterations in the Golgi apparatus and interrup-tion of the packaging of protein into secretory granules