Alkali therapy extends the period of survival during hypoxia: studies in rats

The goal of this study was to evaluate whether sodium bicarbonate might be a useful form of therapy for hypoxic L-lactic acidosis; our aim was to determine if alkali could extend the time of survival in this setting. Hypoxia was induced in anesthetized, paralyzed, artificially ventilated rats by lowering inspired O2 to 5.5%, an amount sufficient to develop a severe degree of L-lactic acidosis. Measuring arterial blood gases frequently permitted maintenance of a near-constant arterial O2 content. Three groups of hypoxic rats were studied: first, no infusions (n = 10); second, sodium bicarbonate at a rate equal to H+ production in the no-infusion group (n = 12); and third, a control for the Na load in the second group as NaCl (n = 17). Survival was close to twofold longer in the sodium bicarbonate group. Part of this beneficial effect seemed to be increased anaerobic glycolysis, producing ATP along with L-lactic acid. In addition, there was a large decrease in the metabolic demand (consumption of O2) in the 7- to 15-min period in the sodium bicarbonate group. Rats exposed to hypoxia and infused with NaCl for 15 min or alkali for 15, 27, or 40 min were then returned to room air; all survived for the subsequent experimental period of 150 min. We found that there is both a rationale and experimental evidence for giving sodium bicarbonate to prolong survival during hypoxia.

Regulation of ethanol metabolism in the rat

The purpose of these experiments was to examine the factors which regulate ethanol metabolism in vivo. Since the major pathway for ethanol removal requires flux through hepatic alcohol dehydrogenase, the activity of this enzyme was measured and found to be 2.9 mumol/(min X g liver). Ethanol disappearance was linear for over 120 min in vivo and the blood ethanol fell 0.1 mM/min; this is equivalent to removing 20 mumol ethanol/min and would require that flux through alcohol dehydrogenase be about 60% of its measured maximum velocity. To test whether ethanol metabolism was limited by the rate of removal of one of the end products (NADH) of alcohol dehydrogenase, fluoropyruvate was infused to reoxidize hepatic NADH and to prevent NADH generation via flux through pyruvate dehydrogenase. There was no change in the rate of ethanol clearance when fluoropyruvate was metabolized. Furthermore, enhancing endogenous hepatic NADH oxidation by increasing the rate of urea synthesis (converting ammonium bicarbonate to urea) did not augment the steady-state rate of ethanol oxidation. Hence, transport of cytoplasmic reducing power from NADH into the mitochondria was not rate limiting for ethanol oxidation. In contrast, ethanol oxidation at the earliest time periods could be augmented by increasing hepatic urea synthesis.