Metabolism of lactate by the intact functioning kidney of the dog

Leal-Pinto, Edgar; Hc, Park; King, Franklin; MacLeod, Martha B.; Rf, Pitts

doi:10.1152/ajplegacy.1973.224.6.1463

Cited by 53 publications

(20 citation statements)

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“…Thus, there is little information on the regulatory function of plasma substrates in acidosis. It has been reported that ammonia excretion is diminished by the administration of glucose [83] or ketone bodies [84] which are also inhibitory in vitro [85], The contribution of non-nitrogenous fuels, such as lactate, to renal oxidation, can also alter in acidosis [86]. The significance of these results has not been fully elucidated.…”

Section: Role Of Circulating Modifiersmentioning

confidence: 99%

Biochemical Aspects of Renal Ammonia Formation in Metabolic Acidosis

Da¹

1975

Enzyme

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In omnivorous creatures, the diet is acidogenic, especially as a result of the meat content, which gives rise to phosphoric and sulphuric acids, i.e., to metabolic acidosis. In the short term, metabolic acids are buffered by tissue proteins and bicarbonate (the ‘alkali reserve’). In the longer term, acid must be excreted, or neutralized with base which is also generated from the diet, by conversion of dietary amino-nitrogen to ammonia. The final steps of this process occur in the kidney, which converts circulating glutamine to ammonia, and to carbon products such as glucose and carbon dioxide, by metabolic reactions which adapt during acidosis to generate more ammonia and maintain an increased renal ammonia content. The complex mechanisms which govern the formation of ammonia, glucose and carbon dioxide from glutamine, involving the reactions of amino acids, the tricarboxylic acid cycle, and gluconeogenesis, are reviewed.

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Section: Role Of Circulating Modifiersmentioning

confidence: 99%

Biochemical Aspects of Renal Ammonia Formation in Metabolic Acidosis

Da¹

1975

Enzyme

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“…However, in the normal animal, the major sources of fuel for the kidneys are free fatty acids and lac tate [2,20], but during acidosis, significant ly more glutamine than lactate is oxidised [26]. It is possible that glutamine itself may provide the acetyl-CoA required for its com plete oxidation in the Krebs cycle.…”

Section: Discussionmentioning

confidence: 99%

Effects of Inhibition of Phosphoenolpyruvate Carboxykinase on Ammonia Production by the Rat Kidney

Bennett

Alleyne

1978

Kidney Blood Press Res

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Phosphoenolpyruvate carboxykinase (PEPCK) in the renal cortex shows the expected increase in activity but oxal acetate decarboxylase and malic enzyme, two other enzymes capable of providing precursors for use in the total oxidation of glutamine by the kidney, showed no change in their activity as a result of metabolic acidosis in rats. 3-Mercaptopicolinic acid, a substance which inhibits PEPCK, caused a 23% decrease in the oxidation of glutamine to CO₂ by kidney cortical slices in vitro. 3-Mercaptopicolinic acid in vivo had anomalous effects on gluconeogenesis but consistently inhibited ammoniagenesis by kidneys of normal as well as acidotic rats.

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“…Pressure was kept approximately constant at the desired value by continually adjusting the screw driver on the inflation device. Calculations of total renal CO2 production and renal CO2 derived from oxidation of glutamine and lactate were made as described previously (9)(10)(11) . 2); the slope of the regression line is unity and P < 0.001 that such a correlation could occur by chance.…”

Section: Methodsmentioning

confidence: 99%

“…These studies were performed during infusion of L-[U-'4C]glutamine into dogs in chronic metabolic acidosis and during infusion of L-[U-'4C]lactate into dogs in chronic metabolic alkalosis. In previous experiments, the percent of total CO2 produced from glutamine averaged 40% in acidosis (10) and 47% from lactate in alkalosis (11). We, therefore, performed our experiments under conditions in which production of CO2 from glutamine and lactate is highest, hence error is lowest.…”

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confidence: 98%

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Renal CO2 production from glutamine and lactate as a function of arterial perfusion pressure in dog.

Baruch¹,

Eun²,

MacLeod³

et al. 1976

Proc. Natl. Acad. Sci. U.S.A.

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The energy cost of renal function in the intact kidney of the dog was assessed at a series of arterial perfusion pressures. Pressure was varied by partially inflating a balloon at the tip of a catheter positioned in the aorta above the origins of the renal arteries. Either L{ U-'4C]glutamine or L-U-14C] lactate was infused intravenously in tracer amounts throughout each experiment. Total renal CO2 production and 14C02 production from each isotope permitted assessment of total renal oxidative metabolism and the proportions derived from the two major substrates of the kidney. Stepwise inflation of the aortic balloon progressively lowered glomerular filtration rate, renal blood inflow, filtered and consequently reabsorbed Na+, total renal CO2 production, and 14CO2 derived from glutamine and lactate. The percent of total CO2 derived from lactate decreased more or less in proportion to the decrease in percent of total CO2 produced. Results were consistent with the view that reabsorption of sodium is the major energy sink of the kidney. They suggest that the oxidation of glutamine supplies energy for tubular transport and basal demands such as synthesis of hormones and maintenance of structure, whereas the oxidation of lactate supplies energy mainly for transport activities. The oxidative metabolism of the kidneys differs from that of other organs in at least two respects. First, the kidneys extract much less oxygen from each 100 ml of arterial blood than other organs do: on average, 1.5 ml in comparison with 4-15 ml (1). Second, the extraction of oxygen remains relatively constant at 1.5 ml/100 ml even though flow is reduced to as little as one-third of normal (2). The first difference does not mean that the energy cost of renal function is small. Blood flow and oxygen consumption are both large. The kidneys, which together constitute 0.5% of body weight, consume 5-8% of the oxygen consumed by the entire body at rest (1). Renal blood flow averages 20-25% of cardiac output at rest (1). The second difference derives from the fact that at normal perfusion pressures, the kidneys filter large volumes of plasma through their glomeruli and then face the energy-demanding task of actively reabsorbing the bulk of the components of the filtrate (3-9). In contrast, low perfusion pressure is commonly associated with low filtration rate and low rate of energy expenditure for reabsorption.Most renal physiologists believe that the major energy cost of renal function is related to the cost of reabsorbing sodium. It has been estimated that 20 to 30 sodium ions are reabsorbed for each molecule of oxygen consumed (3-9). Thus, in man, approximately 28,000 meq of sodium, contained in the 200 liters of plasma filtered each day, are reabsorbed at an energy cost equivalent to the consumption of 1200 mmol of oxygen (1). Energy must also be expended in biosynthesis of hormones and in maintenance of cellular structure.The experiments described in this paper were designed to measure the utilization of glutamine and lactate as fuels of do...

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Metabolism of lactate by the intact functioning kidney of the dog

Cited by 53 publications

References 0 publications

Biochemical Aspects of Renal Ammonia Formation in Metabolic Acidosis

Biochemical Aspects of Renal Ammonia Formation in Metabolic Acidosis

Effects of Inhibition of Phosphoenolpyruvate Carboxykinase on Ammonia Production by the Rat Kidney

Renal CO2 production from glutamine and lactate as a function of arterial perfusion pressure in dog.

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