RT Journal Article
SR Electronic
T1 Effect of cyclic AMP phosphodiesterase inhibitors on cardiac sarcolemmal 5'-nucleotidase.
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 489
OP 493
VO 217
IS 2
A1 Heyliger, C E
A1 Panagia, V
A1 Dhalla, N S
YR 1981
UL http://jpet.aspetjournals.org/content/217/2/489.abstract
AB Two different membrane preparations (fraction HL and fraction S) were used to study the effect of caffeine, theophylline, dipyridamole and papaverine on cardiac sarcolemmal 5'-nucleotidase. Caffeine and theophylline inhibited the 5'-nucleotidase in both fractions, but theophylline appeared to be a more potent agent. The inhibitory effect of caffeine seemed to be the same in both membrane preparations, but the enzyme in fraction S appeared to be more sensitive to theophylline than that present in fraction HL. The inhibition was of the competitive type in both preparations. The inhibitory effect of caffeine and theophylline on 5'-nucleotidase may not be related to their actions on phosphodiesterase since dipyridamole and papaverine, which are also known to inhibit phosphodiesterase, did not affect the 5'-nucleotidase activity. It is suggested that by inhibiting 5'-nucleotidase, caffeine and theophylline may influence the production of adenosine in the myocardium and thereby may interfere with an important mechanism for the regulation of coronary blood flow.