Cmq. Jesus-morais et al., Yangambin, a lignan obtained from Ocotea duckei, differentiates putative PAF receptor subtypes in the gastrointestinal tract of rats, PLANTA MED, 66(3), 2000, pp. 211-216
We investigated the presence of PAF receptor subtypes in the tissues of the
gastrointestinal tract, airways, blood vessels and in murine macrophages.
For this purpose we have used a competitive PAF receptor antagonist, yangam
bin (YAN), extracted from the Brazilian plant "louro de cheiro" (Ocotea duc
kei Vattimo). Rat duodenum, jejunum, ileum, colon, stomach fundus, trachea
and bronchia were removed and 1.5-2 cm muscle segments from those regions w
ere mounted in a 10 ml organ bath with aerated physiological solution at 37
degrees C. PAF evoked a contraction of the rat jejunum, ileum, colon and s
tomach fundus. The contraction was slow and resistant to wash and was follo
wed by desensitization to further doses of PAF. Contractions induced by PAF
(10(-6) M) were inhibited by YAN (10(-7) to M - 2 x 10(-5) M) and WEB 2086
(10(-6) m to M-5 M) in rat jejunum, ileum and colon but not in the stomach
fundus. In the rat stomach fundus only WEB 2086 (5 x 10(-6) M) was able to
block PAF-induced contraction. The contractions induced by acetylcholine,
histamine, 5-hydroxytryptamine and vasopressin were not inhibited by prior
administration of YAN. Yangambin also significantly inhibited PAF-induced v
ascular permeability in rat duodenum, jejunum, ileum, colon, and mesentery.
Yangambin significantly inhibited PAF-induced lipid body formation in mice
peritoneal macrophages. We suggest that YAN is a selective PAF antagonist
which is able to discriminate putative PAF receptors subtypes present in th
e stomach fundus.