The present study was designed to investigate the blocking of calcium
by the hydroalcoholic extract of Tapinanthus dodoneifolius
(Tapidod), "in vitro" on rat trachea. To evaluate this effect, the
contractile activity of tracheal chains from Wistar Kyoto rats was
isometrically recorded. On the isolated tracheal rings the extract
produced the following effects: (a) a reduction of the contraction
obtained by BaCl2, (b) a bronchorelaxing action, on strips
precontracted by KCl, which was not influenced by TEA (3x10-3 M), (c) a
concentration-dependent decrease of the spasm evoked by calcium
chloride (CaCl2) in K+-rich Ca2+-free physiological salt solution,
before and after intracellular calcium depletion (d), an inhibitory
effect on contraction induced by acetylcholine in Ca2+-free
Krebs-Heinseleit solution supplemented with EDTA (5x10-4M). It is
concluded that: 1. The activation of the potassium channels does not
play a significant role in the relaxant effect of Tapidod. 2. The
antispasmodic property of Tapidod seems to be mediated by the blockade
of intracellular Ca2+ release. 3. Most likely an inhibition of the
intracellular Ca2+-regulating proteins is involved
