Honey has antibacterial activity, promotes healing, and enhances immunity. Its acidity, osmotic effects of its high content of sugar, and hydrogen peroxide are assumed to be responsible for its effects. In this study, various honeys were investigated for the presence of nitrite/nitrate, the stable nitric oxide (NO) metabolites, and the effects of intravenous infusion of honey on urinary and plasma NO end products were studied in healthy sheep. Seven kinds of honey, different in their origin (three from Yemen, two from the United Arab Emirates, one from Germany, and one from India), color, and duration of storage, were investigated for the presence of NO metabolites. The assessment of NO metabolites was performed before and after exposure of the honey samples to heating (80 degrees C for 1 hour) or ultraviolet light (for 24 hours). Seven healthy male sheep were used for the study. Fresh unprocessed yellow honey (2 g/kg of body weight) was infused over a period of 45 minutes to each fasting sheep. Plasma and urinary NO metabolites were measured before and after the infusion. All the honey samples examined had various concentrations of NO metabolites; the highest concentration was in the fresh dark honey collected from Yemen, and the lowest in 1-year-stored dark honey collected from India. Darker or fresh honeys contained more NO metabolites than light or stored honey. After heating, NO metabolites decreased in all the kinds of honey. After ultraviolet exposure, NO metabolites were decreased in four kinds of honey, increased in one kind, and unchanged in two kinds. The darker stored honey had more resistance to heating and ultraviolet exposure. Intravenous infusion of honey elevated urinary NO metabolites from 8.4 +/- 7.4 micromol/L to 14.9 +/- 10 micromol/L during the first 60-90 min after infusion and to 35.2 +/- 34 micromol/L during the next 150-180 min. Plasma NO metabolites were increased during 1, 2, and 3 hours after infusion by 3%, 3.6%, and 17%, respectively. No side effects were reported with the use of intravenous honey. It might be concluded that honey contains various concentrations of NO metabolites. Its intravenous infusion increased plasma and urinary NO metabolites. It is assumed that NO might be responsible, in part, for the biological and therapeutic effects of honey.