Biological activities of Lipoxin A include lung strip contraction and dilation of arterioles in wiwo

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Abstract
Biological activities of Lipoxin A include lung strip contraction and dilation of arterioles in vivo. Acta Physiol Scand130, 643–647. Received 7 December 1986, accepted 27 February 1987. ISSN 0001–6772. Departments of Physiology and Physiological Chemistry, Karolinska Institute, and Department of Experimental Medicine, Pharmacia AB, Sweden.Lipoxin A ([5s,6r,15s]‐5,6,15–trihydroxy‐7,9,13–trans‐II‐cis‐eicosatetraenoic acid), a recently characterized lipoxygenation product of arachidonic acid, in submicromolar concentrations elicited long‐lasting contractions of the guinea‐pig lung strip. The response to lipoxin A was not due to release of acetylcholine, histamine, noradrenaline or cyclo‐oxygenase products. 15–hydroperoxyeicosatetraenoic acid (15–HPETE), one precursor of lipoxin A, also contracted the lung strip, but 15–HPETE was less potent and the response was comparatively short‐lived. Furthermore, lipoxin A was inactive on the guinea‐pig trachea whereas 15–HPETE relaxed this preparation. Lipoxin A was also inactive on the guinea‐pig ileum. Intravital microscopy of the hamster cheek pouch disclosed that lipoxin A, as well as 15–HPETE, induced arteriolar dilation but had no effects on microvascular permeability or leucocyte adherence to venular endothelium. Taken together, the leucocyte product lipoxin A displayed a pattern of activity in spasmogenic assays and on the microvasculature that was distinct from those known for prostaglandins, thromboxanes and leukotrienes. The findings indicate that lipoxin A is an additional arachidonic acid derived autacoid with biological actions on smooth muscle in vatro and in vivo.

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