The electric organ of Discopyge tschudii: Its innervated face and the biology of acetylcholinesterase

1. An ultrastructural, histochemical, and biochemical study of the electric organ of the South American Torpedinid ray, Discopyge tschudii, was carried out. 2. Fine structural cytochemical localization of acetylcholinesterase (AChE) indicated that most of the esterase was associated with the basal lamina. Electron microscopy indicated no marked differences in the electrocyte ultrastructure between Discopyge and Torpedo californica. 3. Discopyge electric organ possessed three molecular forms, two asymmetric forms (16 S and 13 S) and one globular hydrophobic form (6.5 S). The asymmetric 16 S AChE form was solubilized by heparin, a sulfated glycosaminoglycan, suggesting that heparin-like macromolecules are involved in the binding of the enzyme to the basal lamina. 4. Our results show that cell-free translated AChE peptides, synthesized using Discopyge electric organ poly (A⁺) RNA, correspond to a main band of 62,000 daltons which probably represents the catalytic subunit of the asymmetric AChE.