The effects of Securidaca longepedunculata root extract on ionic currents and contraction of cultured rat skeletal muscle cells

The effects of the primary extract roots of Securidaca longepedunculata wer e tested on sodium, calcium and potassium currents in rat skeletal muscle c ells developed in culture. In addition, they were tested on depolarisation- induced contraction and resting intracellular calcium levels. S. longepedun culata extract (10(-6) g/l) increases sodium current at all potentials. No clear effect was observed on calcium current except for a slight increase a t negative potentials (-30, -10 mV) revealing a 5 mV shift towards negative potentials of the I-Ca/V curve, as with potassium current. In contrast, at the same concentration, 5. longepedunculata enhanced the contractile respo nse elicited by durable depolarisation. This was not attributable to the sl ight increase in resting intracellular free calcium concentration which did not change during and following S. longepedunculata application. These res ults strongly suggest that S. longepedunculata root extract contains one or more components acting on the voltage-sensor of excitation-contraction cou pling (dihydropyridine receptors), regardless of its implication as a calci um channel. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.