Smooth muscle inhibition by an extract of Sesbania drummondii

The acute effects of an extract of Sesbania drummondii were assessed in vitro on the smooth muscle contractility of intestine and lung parenchyma in the chicken and aortic arch in the rat. Dose-response contraction curves for histamine, carbachol, and norepinephrine were obtained in the ileal, parenchymal, and aortic strips, respectively. After washing was completed, the strips returned to baseline tensions and then were incubated for 10 minutes with an ethyl acetate extraction fraction of S drummondii (molecular weight less than 500). Dose-response curves to the same agonists were repeated at the end of the incubation period. Contractile responsiveness of chicken ileum was little affected by acute incubation of the tissue with the extract. Comparison with the great inhibition of in vitro ileal contractility seen previously in chickens with chronic toxicosis indicated that intestinal inhibition was not due to acute effects of sesbania, but required time for a toxic metabolite to be formed or for damage to occur from affected vasculature. Contractile responsiveness of chicken lung parenchyma to histamine (10(-5) M and 10(-4) M) was significantly decreased, as was rat aortic responsiveness to norepinephrine (10(-7) M to 10(-4) M). Responses in parenchyma were not as greatly inhibited as those in tissue from animals with chronic toxicosis. Greatest inhibition of contractility was seen in the vascular strips, indicating that vascular inhibition has a role in pathologic changes. To test the vasculature inhibition effect in vivo, anesthetized, catheterized rats were given 100-microliter aliquots of dilutions of the extract, IV.(ABSTRACT TRUNCATED AT 250 WORDS)