Prostaglandin release from cat and dog spleen.

1. The output of prostaglandins from the spleens of cats and dogs was studied. Comparison is made between the results found in the two species. 2. The release of prostaglandins was investigated in isolated saline-perfused spleens and in incubates of spleen slices. Release in response to nerve stimulation, and exposure to adrenaline or noradrenaline was compared with resting release. 3. A resting release of prostaglandins was found in the dog but not in the cat spleen. 4. Whereas stimulated dog spleens released microgram quantities of prostaglandins E2 and F2alpha, prostaglandin output from the cat spleen under similar conditions was undectectable or barely detectable. 5. The identity of the prostaglandins released from the dog spleen (prostaglandins E2 and F2alpha) was confirmed by mass spectrometry. 6. The species difference in prostaglandin output from the spleen is discussed in relation to the hypothesis that endogenous prostaglandins modify the responses of this organ to nervous stimuli.