Biphasic action of platelet-activating factor on isolated guinea-pig ileum.
1-0-Hexadecyl-2-0-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor) at 10(-10)-10(-9) M induced slow contraction of isolated guinea-pig ileal muscles and the contraction persisted for a long time. At a higher concentration of 10(-7) M, this phospholipid induced more rapid, but not greater, contraction. At higher concentrations (10(-6)-10(-5) M), this phospholipid induced a biphasic response: rapid contraction followed by relaxation. At high concentrations, this compound inhibited acetyl-choline-induced contractions. The stimulatory effect of this phospholipid was ca. 300 times that of 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphocholine, while its inhibitory potency on induced contraction was similar to those of 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphocholine and its lyso derivative. It was suggested that the differences in effects on contraction of different concentrations of 1-0-hexadecyl- and 1-palmitoyl-2-0-acetyl-sn-glycero-3-phosphocholine were due to the effects of these compounds on the ileum: a strong stimulatory effect and a moderate inhibitory effect on contraction.
D000818:Animals; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects*; D008244:Lysophosphatidylcholines / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D010972:Platelet Activating Factor / Q000494:pharmacology*
D008244:Lysophosphatidylcholines; D010972:Platelet Activating Factor