Blood Oxygen Transport and Prooxidant-Antioxidant Balance in Rats under Hypothermia and Rewarming Combined with a Modification of L-arginine-NO Pathway

hypothermia, rewarming, hemoglobin-oxygen affinity, nitric oxideIntroduction: The study of processes and functional regulation in body under the changed (including the lower) body temperature is the important medical problem. Increase of body resistance to low environmental temperature is especially important for the patient reanimation after the cold exposure, and the assessment of mechanisms creating the tissue oxygen flux may help the development of ways for reanimation of a cooled body. Aim: Study effect of N-nitro-L-arginine methyl ester, L-arginine, or sodium nitroprusside on the blood oxygen transport and the prooxidant-antioxidant balance during hypothermia and rewarming in rats. Methods: Cold exposure was performed in male rats (body weight 200-250 g, n = 54) for 120 min under the box water temperature of 19°C; rewarming took the next 120 min, with a mean rate of 0.06°C/min. N-nitro-L-arginine methyl ester, L-arginine, or sodium nitroprusside were administered intravenously during the second 60 min of hypothermia in 1 mL of saline. Hemoglobin-oxygen affinity was evaluated by p50 (blood pO2 at its 50% O2 saturation) determined by the "mixing" method at 37C, pH 7.4 andpCO2 40 mm Hg and at actualpH, pCO2 and temperature. We were analyzed the antioxidant protection (catalase activity, a-tocopherol) and lipid peroxidation (conjugated diene, Schiff bases). Results: Infusion of L-arginine promoted the higher cold resistance and oxyhemoglobin dissociation curve shift rightwards, thereby reducing the hypoxic signs. It enhanced the antioxidant defense and reduced the levels of lipid peroxidation products, thereby providing the least prooxidant-antioxidant disbalance during the rewarming. However, other modifiers of L-arginine-NO pathway (N-nitro-L-arginine methyl ester, sodium nitroprusside) had not such effect. Conclusion: The L-arginine effect mediated by hemoglobin-oxygen affinity change may be used for the correction of metabolic disorders and improvement of body resistance to low environmental temperature