The Saccus Vasculosus of the Rainbow Trout, Salmo Gairdneri Richardson

Abstract

The general cell metabolism of coronet cells of the saccus vasculosus of the rainbow trout, Salmo gairdneri Richardson, is clearly aimed at energy production, which may take place under aerobic as well as anaerobic conditions. The coronet cells are equipped with a structure (glycocalyx) and contain enzymes (alkaline phosphatase, acetylcholinesterase, (Na + + K + )-ATPase) which are generally connected with transport of ions and low-molecular organic substances. Lipids are not present in demonstrable quantities; the marked amounts of glycogen in coronet cells must therefore be considered as the energy source for the transcellular transport and for the extrusion of low-molecular substances, particularly of cations. No signs have been found of release of acid mucopolysaccharide by coronet cells into the cerebrospinal fluid. The role of this substance, as a possible intracellular ion-exchanger, has been discussed. The metabolism of the glial cells of the saccus vasculosus is aimed at synthesis, which may take place under aerobic as well as anaerobic conditions. Glycogen is mainly metabolized in the pentose phosphate cycle and therefore seems to be of lesser importance as energy source. Indications of a resorbing and transporting, secretory or sensory function of glial cells have not been observed. The high synthetic activity in the glial cells may point to a modulating and stabilizing function-similar to glial-neuron relations in the central nervous system-with regard to coronet cells.