Ribeiriio P d t o , S.P., B r a d
ABSTRACTThe South American rattlesnake venom gland is made up of secretory tubules lined by a simple columnar epithelium containing horizontal cells, mitochondria-rich cells, and the principal cell type, the columnar secretory cells. This cell has a round basal nucleus and abundant rough endoplasmic reticulum, the cisternae of which are variably distended with flocculent material containing many dense intracisternal granules. The supranuclear Golgi apparatus is spherical, with stacks of flattened saccules at the periphery and large vacuoles containing masses of dense material, and other dense granules in the center. Similar but smaller granules are present at the apex where they fuse with the microvillus-covered apical membrane and release their content into the lumen. Protein synthesis was studied in snakes injected with 3H-tyrosine and sacrificed at several times after injection. Radioautographs showed reactions at one half and one hour over the ribosomes and membranes of the rough endoplasmic reticulum. At two hours the immature face of the Golgi apparatus was labeled. At four hours Golgi saccules and vacuoles with dense masses (secretory granules) were labeled, and at eight hours the dense masses within the secretory granules were heavily labeled both in the Golgi region and in the apex near the lumen. Labeled material was found in the lumen at two days. Intracisternal granules were first labeled at eight hours, and by two days reactions remained only over the flocculent content and intracisternal granules of the rough endoplasmic reticulum. Thus, venom protein was synthesized on the rough endoplasmic reticulum, migrated through the Golgi apparatus and accumulated in the dense masses of the secretory granules, which moved to the apex and were extruded. The labeling of intracisternal granules at eight hours and two days after injection indicated a storage nature for these granules.The venom glands of snakes are modified salivary glands with several cell types in their secretory epithelium (Kochva and Gans, '64, '65, '66, '70; Odor and Gennaro, '60; Odor, '65). With the exception of the work of Odor ('65), and more recently of Kochva and Gans ('70) and , no systematic study of the fine structure of the venom glands was found. Also, no dynamic studies, using radioactive precursors and electron microscopic radioautography have followed the cellular events involved in venom synthesis and secretion.Most radioautographic work on protein formation has been done on small mammals such as rats and mice (Leblond, '65) because of their availability and ease of handling. Despite this, many other organisms have systems which lend themselves much better to studies of protein synthesis. Among these systems are the exocrine venom glands of poisonous snakes. These glands produce large quantities of proteins, some of which have been well characterized and shown to possess the harmful enzymatic or neurotoxic properties of the venom (Gosh and Sarkar, '56). In addi-
WARSHAWSKY, HADDAD, GONCALVES,...
