Effects of theophylline, beta-adrenergic stimulants and prednisolone on platelet and urine cyclic guanosine monophosphate (cGMP).

Abstract

Experiments were carried out to investigate the effects of anti-asthma drugs on cGMP levels. In vitro, theophylline (5 X 10(-4) M) increased basal and 5-hydroxytryptamine stimulated cGMP formation by platelets (p less than 0.05) while salbutamol and prednisolone produced no change. No significant differences were found in urine cGMP levels in healthy subjects, after short term treatment with theophylline, isoprenaline or prednisolone. Urinary cGMP levels were lower than normal in the majority (7/10) of asthma patients tested and in female patients this difference was significant (p less than 0.05). Severity of asthma symptoms were not found to be associated with particular changes in urinary cGMP levels. Fluctuations in the cGMP levels were, however, greater (p less than 0.01) in asthma patients with a more unstable respiratory condition. The differences between in vitro and in vivo results may demonstrate that beta-stimulants and theophylline have different acute and chronic effects on cGMP formation, or show that in vivo these drugs primarily affect tissue enzymes that differ from those on platelets.