Stimulation of Lymphocyte Release from the Spleen by Theophylline and Isoproterenol

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Abstract
The effect of theophylline and isoproterenol on the splenic release of lymphocytes into the blood was studied in guinea pigs by the comparison between the content of cells in splenic afferent and efferent blood, combined with determination of the blood flow through the spleen.An intracardial injection of theophylline, like that of isoproterenol, resulted in a greatly increased release of lymphocytes from the spleen as compared to that in control animals. The effect of theophylline, in contrast to that of isoproterenol, could not be abolished by pretreatment with propranolol. The similar effects of theophyliine (known to inhibit the degradation of cAMP) and isoproterenol (known to stimulate the synthesis of cAMP) on the splenic release of lymphocytes to the blood suggest that these effects may be mediated by an increase of intra‐cellular cAMP. This suggestion is supported by our finding of an additive effect when theophylline and isoproterenol were administered in combination.The abovementioned release of lymphocytes was found shortly after administration of the drugs. After isoproterenol it was followed by an inhibited release of lymphocytes from the spleen. This was in contrast to the much longer duration of the releasing effect of theophylline.