l-Arginine, 8-bromo-cAMP, dimethyl sulfoxide (DMSO),
forskolin, isobutyl-methylxanthine, (−)isoproterenol, KT 5720, KT
5823, NG-nitro-d-arginine methyl ester
(d-NAME), NG-nitro-l-arginine
methyl ester (l-NAME), dl-propranolol, sodium
nitrite, and TCA were purchased from Sigma (Buchs, Switzerland). Griess
reagent was obtained from Merck (Darmstadt, Germany). HBSS was
purchased from Gibco (Basel, Switzerland). All drugs were made up fresh
the day of the experiment. The drugs were dissolved in HBSS except for
forskolin, KT 5720, and KT 5823, which were dissolved in DMSO and
isoproterenol for which ethanol was used. The final maximal
concentration in a well for DMSO and ethanol was 0.1% and 0.01%,
respectively.