EFFECT OF MECHANICAL PRESSURE ON C-FOS AND ON THE MITOTIC-ACTIVITY OFEPIDERMAL-CELLS

A dosed mechanical pressure of 12.5 kg/cm(2) applied for 1 min on depi lated mouse skin did not cause cellular death or visible alterations o f the cellular ultrastructures. However, it had a strong effect on the mitotic cycle of the epidermal cells - stimulating the cells to enter the mitotic cycle and temporarily blocking the G1 --> S transition. T his effect was strictly limited to the pressed area of the skin. The p roto-oncogene c-fos was induced within the first 2 min following appli cation of the pressure. The level of c-fos mRNA showed two peaks durin g the next 24 h. The first slight peak was preceded by a rapid increas e in the cAMP level in the pressed skin, the second - by a fall in the cAMP concentration. A model is suggested to explain the observed effe cts by reversible functional damage of the cellular membrane affecting the enzymes maintaining the steady state level of cAMP.