Growth Factor-treated PC12 Cells Research Articles

Characterization of the K+ channel opening effect of the anticonvulsant retigabine in PC12 cells.

Retigabine (D-23129) is a new anticonvulsant compound which acts as a K+ channel opener in neuronal cells. The aim of the present study was to further characterize the retigabine induced K+ current. In nerve growth factor treated PC12 cells and in rat cortical neurones the application of retigabine activated a K+ current. In contrast, however, no K+ current activation was observed in untreated PC12 and in glial cells which were cultivated together with the neuronal cells. To characterise the retigabine activated K+ current, K+ channel blockers were used. The retigabine induced current was not affected by 1 and 10 mM 4-aminopyridine (4AP). Ba2+ 1 mM resulted in a reduction of 88.6+/-3.0% (n = 5); 10 mM abolished the current. Tetraetylamonium (TEA), 1 and 10 mM, reduced the current by 23.6+/-3.1 and 61.6+/-3.7%, respectively. To investigate the current/voltage (I/V) relation of the current initiated by retigabine (10 microM), cells were clamped to a holding potential of -80 mV and a ramp stimulation protocol (-120 to +60 mV in 5 s) was applied prior to and during application of retigabine. Subtraction of the two traces yielded the current induced by retigabine. A nearly linear relationship was determined between - 120 and -40 mV. At potentials positive to - 40 mV, the response was variable. This was due to the additionally observed weak blocking effect of retigabine on delayed rectifier (Kdr) currents. If the ramp was applied in the presence of 10 mM 4AP to block Kdr, a nearly linear I/V-relationship was present from -120 to +60 mV. The comparison of the I/V relation and pharmacology with published K+ channel subtypes gives evidence that an unknown neuronal K+ channel subtype may be involved.

Lack of correlation between 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and lovastatin resistance in nerve growth factor treated PC-12 cells

1. The relationships among the mevalonic acid (MVA) forming enzyme, 3-hydroxy-3-methylglutaryl coenzyme A (CoA) reductase, cell growth and differentiation, and the cytotoxic effects of the reductase inhibitor lovastatin were studied in PC-12 cells, exposed to growth factors. 2. When added individually, nerve growth factor (NGF), basic fibroblast growth factor, and epidermal growth factor induce an increase in HMG-CoA reductase activity in cells grown in serum-containing medium. In the presence of serum, the effect of NGF on HMG-CoA reductase is persistent. 3. Short-term serum starvation and long-term NGF treatment, in combination, have an additive effect, resulting in a high reductase activity. 4. Unlike serum and MVA, which downregulate levels of HMG-CoA reductase by accelerating its degradation, NGF upregulates reductase by slowing the rate of its degradation. This mechanism, however, appears to operate only in the presence of serum, as after prolonged growth with NGF in serum-free medium, cells have a low reductase activity. 5. PC-12 cells grown in the absence of NGF are highly sensitive to lovastatin (25 microM) and more than 70% of the cells die after 48 hr. NGF confers lovastatin resistance on cells grown in the presence or in the absence of serum (only 30-40% cell death after 48 hr with lovastatin). 6. NGF-induced resistance on lovastatin develops with time and is apparent only in the well-differentiated PC-12 cells whether or not the cells express a high reductase activity.(ABSTRACT TRUNCATED AT 250 WORDS)