Biosynthesis of carnosine in primary cultures of rat olfactory bulb.

Primary cultures of glia cells obtained from adult rat olfactory bulb synthesize carnosine (beta-alanyl histidine). The rate of synthesis increases the older the culture is and is enhanced by the addition of dibutyrylcyclic-AMP (dBcAMP) to the medium. Millimolar concentrations of this agent intensify galactocerebroside (GalC) staining compared to control cultures. Removal of GalC positive cells through antibody and complement cell killing decreases carnosine synthesis to a minimum. Cultures prepared from olfactory bulb of new-born rats contain neuron specific enolase (NSE) positive neurons and GalC positive ensheathing cells. Such cultures produce carnosine. When switched to nerve growth factor (NGF) depleted medium containing dBcAMP the share of neurons in the culture decreases drastically with time and concomitantly an increase of the relative rate of carnosine synthesis is observed. After 1 week in such medium the cultures contain almost no NSE positive cells. Virtually all cells express glial fibrillary acidic protein (GFAP) and are GalC positive. These data suggest that carnosine is synthesized by the ensheathing cells of the olfactory bulb and not by olfactory neurons.