Porphyrin synthesis in primary nervous tissue cultures from 10(-3) M delta-aminolaevulinic acid in the presence of melatonin and neuropeptides.

Of the primary neuronal tissue cultures (glia cell, neuronal cells, mixed and retina cultures), the neuronal cells of (cells + medium) display the highest total porphyrin production from 10(-3) M delta-aminolaevulinic acid (ALA). In the presence of 10(-3)-10(-6) M melatonin, the quantity of total porphyrins produced by the neuronal cultures decreases in inverse proportion to the concentration. Oxytocin, lysine-vasopressin, CCK-8 sulphate ester and des-Tyr-gamma-endorphin in concentrations of 10(-5) and 10(-6) M block the porphyrin synthesis of the glia cells and display different effects on that of the neuronal cells. They enhance the total porphyrin synthesis of the cell cultures, with the exception of 10(-5) M des-Tyr-gamma-endorphin, which exerts an inhibitory effect on the glia cells.