The anatomy of the parotoid gland in Bufonidae with some histochemical findings. II. Bufo alvarius.

The gross and microscopic anatomy of the venom producing parotoid glands of Bufo alvarius has been studied by light and electron microscopy. Histochemical reactions for the presence of venom constituents and of components in biochemical pathways in the synthesis and release of venom were performed. The gland is composed of numerous lobules. Each lobule is an individual unit with a lumen surrounded by a double cell layer. Microvilli of the outer layer interdigitate with microvilli of the inner layer. Cells of the outer layer resemble smooth muscle cells, are rich in adenosine triphosphatase and glucose-6-phosphatase, and contain numerous pinocytotic vesicles, glycogen granules and various organelles. These organelles include "crystalloids" of what seem to be highly organized agranular reticulum. These outer layer cells probably function in some aspects of venom synthesis, active cellular transport and contraction in the discharge of the secretory product. The inner cell layer demonstrates a positive chromaffin reaction, contains steroid material, various organelles, some pinocytotic vesicles and glycogen granules, and appears devoid of a plasmalemma on its inner surface. This layer is probably involved in venom formation and release via an apocrine type of secretion. Bufo alvarius parotid gland shows significant morphological and histochemical differences from that of B. marinus and more nearly resembles a typical steroid producing organ.