MECHANISMS INVOLVED IN THE SPASMOLYTIC EFFECT OF EXTRACTS FROM SABAL SERRULATA FRUIT ON SMOOTH-MUSCLE

1. The effects of two extracts from Sabal serrulata fruits [total lipi dic (L) and saponifiable (S)] on smooth muscle contractions have been assayed. 2. Both extracts (0.1-1 mg/ml) relaxed the tonic contraction induced by norepinefrine (30 nM) on rat aorta [EC(50)) 0.53 +/- 0.05 m g/ml (L) and 0.5 +/- 0.04 mg/ml (S)] and by KCl (60 mM) on rat uterus. The Sabal extracts (0.3-1 mg/ml) also antagonized the dose-response c urve of contractions induced by acetylcholine (0.1-100 mu M) on urinar y bladder. 3. dL-Propranolol(1 mu M) but not the inactive (R)-(+)-prop ranolol(1 mu M) potentiated the Sabal extracts relaxant effect by lowe ring the EC(50) (0.35 +/- 0.2 vs 0.20 +/- 0.01 mg/ml for L and 0.43 +/ - 0.02 vs 0.19 +/- 0.02 mg/ml, P < 0.01, for S extract). 4. Cyclohexim ide (10 mu g/ml) antagonized the effect of extracts from Sabal. Howeve r, actinomycin D (5 mu g/ml) significantly (P less than or equal to 0. 01) antagonized the effect of the total lipidic extract without modify ing that of the saponifiable extract. 5. The relaxant effect of both e xtracts was not modified by the tyrosine kinase inhibitor genistein (1 0 mu M) or the ornithine decarboxylase inhibitor alpha-difluoromethyl- ornithine (10 mM).