Determination of carbon monoxide (CO) in rodent tissue: Effect of heme administration and environmental CO exposure

Carbon monoxide (CO), produced endogenously during heme degradation, is considered a messenger molecule in vascular and neurologic tissues. To study this role, it is important to determine CO concentration in target tissues pre- and post-perturbations. Here, we describe a sensitive and reproducible method, which is linear and accurate, and provide some examples of its application for quantitation of CO concentrations in tissues pre- and post-perturbations. Tissues from adult rats and mice were sonicated (20% w/w), and volumes representing 0.04-8 mg fresh weight (FW) were incubated at 0 degrees C for >= 30 min with sulfosalicylic acid. CO liberated into the headspace was quantitated by gas chromatography. Tissue CO concentrations (mean +/- SD, pmol CO/mg FW) were as follows: blood (47 +/- 10, 45 +/- 5), muscle (4 +/- 4, 10 +/- 1), kidney (5 +/- 2, 7 +/- 2), heart (6 +/- 3 6 +/- 1), spleen (11 +/- 3, 6 +/- 1), liver (4 +/- 1, 5 +/- 1), intestine (2 +/- 1, 4 +/- 2), lung (2 +/- 1, 3 +/- 1), testes (1 +/- 1, 2 +/- 1), and brain (2 +/- 1, 2 +/- 0) in untreated rat (n = 3) and mouse (n 5), respectively. Between the rat and the mouse, only CO concentrations in the muscle and spleen were significantly different (p <= 0.05). Endogenous CO generation, after administration of heme arginate to mice (n = 3)., increased CO concentrations by 0-43 pmol/mg FW. Exposure of mice (n = 3) to 500 ppm CO for 30 min yielded significantly elevated CO concentrations by 4-2603 pmol/mg FW in all tissues over the native state. While blood had the highest CO concentration for all conditions, muscle, kidney, heart, spleen, and liver, all rich in hemoglobin and/or other CO-binding hemoproteins, also contained substantial CO concentrations. Intestine, lung, testes, and brain contained the lowest CO concentrations. (c) 2005 Elsevier Inc. All rights reserved.