Recherches histoenzymologiques sur le système neurosécréteur caudal de quelques Téléostéens ( Cyprinus carpio L., Tinca tinca L. et Salmo fario L.)

Abstract

Comparative histochemical investigations on the localization of some enzymatic activities at the level of the caudal neurosecretory system in three species of freshwater teleosts have confirmed the analogy of this system with the hypothalamo-hypophyseal one: (1) The nonspecific alkaline phosphatase activity is localized in the capillary walls and is lacking in the neurosecretory neurons. (2) The nonspecific acid phosphatase is demonstrable in a sharply defined perinuclear area in the perikaryon of the neurosecretory neurons. (3) The glucose 6-phosphatase activity appears to be uniformly distributed in the cytoplasm and in the capillary walls. (4) An intense ATPase activity is also present in the capillaries, but it is absent from the cytoplasm of the secretory cells. (5) Succinic dehydrogenase and cytochrome-oxidase activities seem extremely weak in the neurosecretory neurons and are lacking in the urophysis. (6) Nonspecific esterases and cholinesterases could not be demonstrated. The occurrence and distribution of the phosphatase activities may be related (acid phosphatase) to the intense elaboration of secretion products within the secretory cells and (glucose 6-phosphatase) to the ensuing high metabolism of these elements. The alkaline phosphatase, ATPase, and glucose 6-phosphatase activities may be associated with transport through the vessel walls in both directions. The extremely low succinic dehydrogenase and cytochrome oxidase activities and the lack of ATPase activity in the cytoplasm of the secretory cells suggest that in these cells the energy may be supplied by nonoxidative processes.