[The reducing effect of prostaglandins on circulating eosinophils in splenectomized rats--on its mechanism (author's...

It is known that Prostaglandins(PGs) have many interesting physiological effects on various tissues, but the reducing effect on circulating eosinophils was still obscure, except for our report in 1975. Our previous report revealed that the effect had not act through beta-adrenergic receptors, because a beta-adrenergic blocker did not inhibit this effect. The present report was carried out to study whether the hypothalamo-hypophyseal-adrenocortical axis would be concerned or not on this effect. PGs(10 mug/kg) were administered intraperitoneally under thiopental sodium anesthesia and blood was drawn from the tail vein of the splenectomized rats. Both PGE1, E2, F2alpha did not decrease the number of peripheral eosinophils on the group of the adrenalectomized rats. Both PGE1, F2alpha did not decrease the number of peripheral eosinophils, but PGE2 had a significant reducing effect on the number of them 2 and 3 hours after administration in the group of the rats with hypothalamic lesions. Both PGE1, E2, F2alpha had a significant reducing effect at the group of the rats with man-made hypothalamic lesions. This effect was almost the same as for the control group just splenectomized. It could be concluded that the eosinopenic effect of PGE1 and PGF2alpha was conducted through the hypothalamus and adrenal glands, but that of PGE2 might be effected through the hypophysis or directly through the adrenal glands.