Midkine, a novel neurotrophic factor, promotes survival of mesencephalic neurons in culture.

Midkine (MK), a retinoic acid responsive gene product, is a novel neurotrophic factor with a molecular weight of 14,000. MK at the optimal concentration of 10 ng/ml promoted the survival of mouse mesencephalic neurons in culture as demonstrated by the increased number of microtubule-associated protein-2 (MAP2) immunostaining-positive and tyrosine hydroxylase immunostaining-positive neurons and an elevated uptake of radiolabeled dopamine. These results suggest that MK has ubiquitous neurotrophic activity towards mesencephalic neurons which contain a large number of dopaminergic neurons.