The Effect of Hyperbaric Oxygenation on the Circulation of Urea in Rats Following Experimental Partial Hepatectomy

Abstract

Material and methods. The studies were performed on 75 white mature rats (females) weighing 180—220g. Partial hepatectomy was performed by resection of a part of the left lobe of the liver (15—20% of the organ weight). Hyperbaric oxygenation (HBO) was performed three times (3 ata, 50 min). The first, second and third sessions were performed 4—8 hours, 24 hours and 48 hours after the surgery, respectively. The urea level was determined in the tissues of visceral organs, as well as in arterial blood (aorta), portal blood, blood from renal and hepatic veins, bile from common bile duct, and in urine on the 1st, 4th and 11th days of posthyperoxic period (days 3, 7 and 14 post-surgery).Results. Activation of the urea incretion from the operated liver to the bloodstream under hyperoxic conditions was accompanied by increased urea concentration in the arterial blood and excretion from the body with urine that was facilitated by the elimination of a stimulating effect of PHE on the reabsorption of urea in the kidneys by the HBO procedure. At the same time, the production of urea in the renal tissue was activated and further released to the circulation through the renal vein. Stimulation of the liver and intestinal urea circulation by HBO was accompanied by the preservation of the stimulating effect of PHE on its accumulation in duodenum and colon tissues. In the thyroid gland, spleen, heart, and lungs of operated rats, HBO activated the transition of the «arterial» urea from the free form to the bound one. Termination of HBO normalized the urea concentration in the arterial blood by the 11th day of the posthyperoxic period whereas urea continued to be accumulated the heart, spleen, lungs, and intestine. A preserved increased release of urea from the operated liver into the bloodstream after HBO was accompanied by partial retention in the hepatocytes of urea delivered via bloodstreem through the portal vein. On the 11th day after HBO, the repeated hyperoxic activation of the liver and intestinal urea circulation occured, as well as HBO-restored stimulation of its production in the kidneys resulted in urea release into the renal vein and excretion with urea.Conclusion. HBO provides a correcting effect on alteration of circulating urea caused by PHE.