Electron-microscopic localization of cholinesterase activity in Pacinian corpuscles of the cat mesentery

The authors studied nCHE activity in Pacinian corpuscles of the mesentery of adult cats and 14-day-old kittens. The localization of nCHE was performed on non-frozen sections in Karnovsky's method (1964) with inhibitor application. The nCHE activity was by means of reaction product deposits always localized on plasmic membranes of inner core lamellae and on the axon axolemma. On capsule lamellae no nCHE activity was found. In inner core cells of Pacinian corpuscles of adult individuals, owing to sporadic occurrence of organelles their relationship to nCHE activity failed to be established. It was possible only in Pacinian corpuscles of 14-day-old kittens, where organelle findings are substantially more frequent and furthermore the lamellae broader, which facilitates the localization of deposits on plasmic membranes. The nCHE activity was proved here on the rough endoplasmic reticulum and on vesicles of the Golgi complex. For the above-mentioned reasons Pacinian corpuscles of kittens are substantially more suitable for the ultrahistochemical localization of enzymes than those of adult cats. The difference in nCHE activity localization, as it was established by Idé and Saito (1980), is probably caused by the different preparation of sections for incubation (cryostat sections were used). The occurrence of nCHE isoenzymes with different binding to the membranes of inner core cells of the Pacinian corpuscle not only renders exact electron-microscopic localization more difficult but it also shows that, similarly as ACHE, nCHE is synthetized in the rough endoplasmic reticulum in soluble oligomeric form. Only after aggregation of these subunits is it bound to the membranous structures of the inner core. The reversibility of this process can explain the irregular findings of the precipitate, mainly on pinocytotic vesicles. The localization of nCHE on inner core cells supports the opinion that inner core lamellae of Pacinian corpuscles are formed by Schwann cells. The nCHE activity found on all inner core lamellae of Pacinian corpuscles from the axon to the capsule lamellae is further evidence for the nonexistence of a special zone of lamellae, the so-called outer core, between the inner core and capsule.