The quantitative bioassay of nerve growth factor: use of frozen 'primed' PC12 pheochromocytoma cells.

A quantitative bioassay for nerve growth factor (NGF) has been previously described which employs PC13 rat pheochromocytoma cells. The basis of this assay is that rapid neurite regeneration by PC12 cells pretreated ('primed') with NGF for at least a week is quantitatively related to the amount of NGF present in the culture medium. The present experiments demonstrate that NGF-pretreated PC12 cells retain their priming for over a year when appropriately frozen and stored and that such frozen cells can be employed for the quantitative bioassay of NGF. The major advantage of this assay is that large numbers of cells can be primed at a time (in suspension culture) and stored in aliquots until future use. The newly described bioassay employs the frozen primed cells essentially as reagents and avoids the need to have freshly primed cultures on hand.