Abstract 388

Carbon monoxide (CO) is produced endogenously during the heme oxygenase (HO)-catalyzed degradation of heme derived from the turnover of hemoglobin and other hemoproteins. Besides being a waste product, CO has recently been implicated as a biological messenger molecule, analogous to nitric oxide, in vascular as well as neurologic tissues. For instance, in the brain, the distribution of HO closely parallels that of soluble guanylyl cyclase. Thus, besides having the methodology to accurately determine the activity of HO (the potential for CO production) in tissues (Anal Biochem 1988;168:31-8), it is equally important to determine the concentration of CO in target tissues pre- and post- perturbations. We have now developed a sensitive method and report on preliminary results. Tissues were harvested from adult male Wistar rats (315 ± 3g, n = 3) and Balb-C mice (26.2 ± 2.2 g, n = 5). Rat and mouse liver, lung, and heart were blanched with ice-cold 100 mM KPO4 buffer. One part tissue was sonicated with three parts of ice-cold buffer. Forty µL of tissue sonicate (10 mg tissue) was incubated with 10 µL of 50% (w/v) sulfosalicylic acid in CO-free vials. After 30-min incubation at 0°C, the CO liberated into the vial head space was quantitated by gas chromatography. The native concentrations of CO in rat and mouse tissues (mean ± SD, pmol CO/mg fresh weight) were, respectively: blood (47 ± 10, 45 ± 5); spleen (11 ± 3, 6 ± 1); heart (96 ± 3, 6 ± 1); kidney (5 ± 2, 7 ± 2); muscle (4 ± 4, 10 ± 1); liver (4 ± 1, 5 ± 1); brain (2 ± 1, 2 ± 0); lung (2 ± 1, 3 ± 1); intestine (2 ± 1, 4 ± 2); testes (1 ± 1, 2 ± 1). Between the rat and mouse tissues only the spleen and muscle were found to have significantly different (p < 0.05) CO concentrations. We conclude that, while blood has the highest CO concentrations, tissues, such as spleen, heart, kidney, muscle, and liver, that are rich in hemoglobin and other hemoproteins, also contain substantial amounts of CO. Brain, lung, intestine, and testes contain the lowest concentrations of CO.