Starikova A. Influence of different factors on differentiation of rat pheochromocytoma PC12 cells.

The thesis is development to investigation of the effect of a high-voltage-activated calcium channel blocker, nifedipine and high KCl level on the cell differentiation. In cells cultured in modified medium containing nifedipine (2.5 mM or 5.0 mM) a decrease of mitotic activity took place on the third day the culturing. An increase of total length and number of processes occurred on the fifth day. In higher concentration (10.0 mM) nifedipine considerably suppressed vital functions of the cells; retraction of processes together with blocking of proliferation activity were observed. In parallel with these changes, on the second day of cultivation in 2.5 mM and 5.0 mM nifedipine containing medium a reduction of [Ca2+]I from 103 ± 6 nM to 50 ± 2 nM was detected. At 10.0 mM concentration of nifedipine in a medium a decrease of [Ca2 +]I was observed on the first day only (to 76 ± 8 nM); then the level of free calcium concentration raised dramatically. Culturing PC12 cells in a medium with 20-30 mM KCl deprive d of nerve growth factor supported cell proliferation and rapid growths of small neurite-like processes. However, their lengths did not increase with prolongation of the time of culturing. During culturing with 40 mM KCl the growth of this processes became blocked; the cells stopped proliferating and showed signs of degeneration. Measurements of [Ca2+]i level during the first days of PC12 cells culturing in a hyperpotassium medium indicate that such changes in this level could be an important factor in the induction of the observed morphological alterations, however, other effects induced by membrane depolarisation may be also responsible for them.