EFFECTS OF HEMIN ON NEURONS DERIVED FROM THE NEURAL CREST

Hemin at high concentrations promoted the survival and neuritic outgrowth in vitro of dissociated sensory and parasympathetic neurons from 8-day-old chick embryos. Similar concentrations of hemin increased the activities of the neutrotransmitter biosynthetic enzymes, tyrosine hydroxylase and choline acetyltransferase, in explant cultures of neonatal rats sympathetic ganglia and in explant and dissociated 14-day-old embryonic chick parasympathetic ganglia, respectively. Enzyme activities of both dissociated neonatal rat sympathetic ganglia and explant and dissociated 8-day-old embryonic chick parasympathetic ganglia were not affected by hemin. Since the neurotrophic effects of hemin were small compared to those of tissue extracts, and were seen mainly at concentrations approaching the limits of its solubility, hemin resulting from the breakdown of heme proteins in tissue extracts is unlikely to contribute significantly to their effects.