Neuronotrophic and neurite-promoting factors: effects on early postnatal chromaffin cells from rat adrenal medulla.

Adrenal chromaffin cells from early postnatal rats maintained in culture have previously been shown to grow neuritic processes and survive better in the presence of nerve growth factor (NGF). In the present study we have quantitated the effects on chromaffin cell (postnatal day (D) 8) survival and neurite outgrowth of: NGF, ciliary neuronotrophic factor (CNTF), activities contained in various types of conditioned media (CM), and various substrata (laminin, fibronectin and polyornithine-binding neurite-promoting factor from RN 22 Schwannoma cells - PNPF). At saturating concentrations CNTF (50 ng/ml) and C6 glioma cell CM, (50-fold concentrated) supported survival over the 4-day culture period of all the chromaffin cells present in culture 2 h after seeding. NGF (50 ng/ml) and the non-concentrated CMs from primary Schwann cell and astrocytes as well as Schwannoma and C6 glioma cell cultures, achieved the maintenance of only about half the number of cells above the baseline survival as compared to CNTF and the concentrated C6-CM. These results are compatible with two subsets of D8 chromaffin cells, one only supported by CNTF and the concentrated CM and the other supported by either NGF or CNTF. Either NGF or CNTF elicited neurite outgrowth from 15-20% of the surviving cells. Combination of maximal doses of NGF and CNTF caused a small increase in neurite recruitment beyond that elicited by either factor alone. Low doses of CNTF added to the effect of NGF, shifting the NGF titration curve by about 4-fold. Neurite outgrowth was also induced by the concentrated, but not the unconcentrated C6-CM. Laminin, fibronectin and PNPF did not affect the fibronectin and PNPF did not affect the recruitment of neurites as compared to a polyornithine substratum unless the cultures were supplemented with a neuronotrophic factor and carried for 7 days. However, even before showing effects on neurite recruitment these substrata affected various neuritic performances, such as length, neurite numbers and endings per cell.