Catecholamines in the coelenterate Renilla köllikeri

Summary The characteristics of uptake of ³H-noradrenaline (³H-NA) and ³H-adrenaline (³H-A) in the tissues of the sea pansy, Renilla köllikeri, were studied by in vivo incubations. Lineweaver-Burk plots indicated two components of catecholamine accumulation, one representing a high-affinity uptake with an apparent K _m of 4.91×10^-7 M (³H-NA) or 4.39×10^-7 M (³H-A), and the other a low affinity process with an apparent Km of 5.52×10^-5 M (³H-NA) or 1.49×10^-5 M (³H-A). The high-affinity uptake of both tracers was strongly inhibited at low temperature and in a calcium-free medium, thus suggesting the involvement of a carrier-mediated transport mechanism, but was largely insensitive to sodium omission and ouabain. Accumulations of ³H-NA, but not ³H-A, were highly desipramine-sensitive.Light-microscopic radioautographic studies demonstrated the presence of cells reactive to both ³H-NA and ³H-A in the ectoderm, mesoglea and endoderm. Extraneuronal accumulations of ³H-NA and ³H-A were prominent in some ectodermal cells, in amoebocytes and spicule cells. Reactive neuronal processes were tentatively identified throughout the mesoglea and over all muscle layers on the basis of several morphological criteria. ³H-A, but not ³H-NA label, was more intense over the presumed photocytic zone and circular muscle than elsewhere. These and other observations support a neurotransmitter role for adrenaline (and probably noradrenaline) in control of luminescence and modulation of slow rachidial contractions.Supported by a grant from the Natural Sciences and Engineering Research Council of Canada