Stimulation by insulin of cell elongation and microtubule assembly in embryonic chick-lens epithelia

Both fetal-calf serum and insulin cause cell elongation in explanted chick-lens epithelia from 6-day-old embryos. We show that 1 mug/ml of insulin, like serum, stimulates a doubling of cell length and an assembly of longitudinally oriented microtubules; colchicine treatment inhibits this cell elongation. In contrast to serum, insulin neither promotes further lens-cell elongation nor appreciably stimulates the synthesis of bulk proteins or of delta crystallin under the present conditions. These data indicate that the early morphological events of lens fiber differentiation can be initiated by insulin in a chemically defined, serum-free medium without significant affects upon protein synthesis.