DIOSMIN-INDUCED INCREASE IN SENSITIVITY TO CA2-MUSCLE CONTRACTILE APPARATUS IN THE RAT ISOLATED FEMORAL VEIN( OF THE SMOOTH)

The effect of diosmin, a flavone derivative, on the Ca2+ sensitivity o f the venous contractile apparatus was investigated in chemically (bet a-escin) skinned strips from the rat isolated femoral vein. Diosmin (0 .5-10 muM) shifted to the left the concentration-response curve to Ca2 + (0.05-5 muM). The maximal effect was observed in the presence of 1 m uM diosmin which increased the contractile response evoked by 0.15 muM Ca2+ from 26.3% to 78.9% of the maximal Ca2+-induced response. This w ork demonstrates that the venotonic action of diosmin involves an incr ease in the Ca2+ sensitivity of the contractile apparatus. Such a mech anism of action could represent a new and important means of therapeut ic control of vasomotor activity.