β-Adrenoceptor responsiveness in intact leukocytes from adults and newborn infants; effect of phosphodiesterase inhibitors

Abstract

Intact mononuclear and polymorphonuclear leukocytes from adults and newborn infants were used to estimate the β₂-adrenoceptor responsiveness in vitro. The accumulation of cAMP in response to receptor stimulation by isoprenaline was used as a measure of the receptor responsiveness. The relevance of the method is dependent on the activity of the cAMP phosphodiesterase inside the cells. The xanthine derivatives, theophylline (4 mmol 1^-1) and 3-isobutyl-1-methyl-xanthine (0.1-2.5 mmol 1^-1), were used to inhibit the cAMP phosphodiesterase activity. It appears that 3-isobutyl-1-methyl-xanthine at 2.5 mmol 1^-1 inhibits the phosphodiesterase activity almost completely. By use of this concentration no age-dependent changes in the isoprenaline-stimulated cAMP accumulation in mononuclear and polymorphonuclear leukocytes from adults and newborn infants could be demonstrated.

Key Words:

• age variation
• cAMP
• isobutyl-methyl-xanthine
• theophylline