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The effect of metabolic acidosis on the synthesis and turnover of rat renal phosphate-dependent glutaminase.

ABSTRACT: Regulation of the mitochondrial phosphate-dependent glutaminase activity is an essential component in the control of renal ammoniagenesis. Alterations in acid-base balance significantly affect the amount of the glutaminase that is present in rat kidney, but not in brain or small intestine. The relative rates of glutaminase synthesis were determined by comparing the amount of [35S]methionine incorporated into specific immunoprecipitates with that incorporated into total protein. In a normal animal, the rate of glutaminase synthesis constitutes 0.04% of the total protein synthesis. After 7 days of metabolic acidosis, the renal glutaminase activity is increased to a value that is 5-fold greater than normal. During onset of acidosis, the relative rate of synthesis increases more rapidly than the appearance of increased glutaminase activity. The increased rate of synthesis reaches a plateau within 5 days at a value that is 5.3-fold greater than normal. Recovery from chronic acidosis causes a rapid decrease in the relative rate of glutaminase synthesis, but a gradual decrease in glutaminase activity. The former returns to normal within 2 days, whereas the latter requires 11 days. The apparent half-time for glutaminase degradation was found to be 5.1 days and 4.7 days for normal and acidotic rats respectively. These results indicate that the increase in renal glutaminase activity associated with metabolic acidosis is due primarily to an increase in its rate of synthesis. From the decrease in activity that occurs upon recovery from acidosis, the true half-life for the glutaminase was estimated to be 3 days.

SUBMITTER: Tong J

PROVIDER: S-EPMC1152995 | biostudies-other | 1986 Jan

REPOSITORIES: biostudies-other

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Response of the mitochondrial proteome of rat renal proximal convoluted tubules to chronic metabolic acidosis.

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| S-EPMC3683795 | biostudies-literature

Dietary acid load and metabolic acidosis in renal transplant recipients.

Project description:Background and objectivesAcidosis is prevalent among renal transplant recipients (RTRs) and adversely affects cardiometabolic processes. Factors contributing to acidosis are graft dysfunction and immunosuppressive drugs. Little is known about the potential influence of diet on acidosis in RTRs. This study examined the association of metabolic acid load with acidosis and with cardiovascular risk factors in RTRs and aimed to identify dietary factors associated with acidosis. DESIGN, PARTICIPANTS, SETTING, & MEASUREMENTS: 707 RTRs were included. Metabolic acid load was assessed by measuring 24-hour urinary net acid excretion (NAE; i.e., titratable acid + ammonium - bicarbonate). Acidosis was defined as serum [HCO(3)(-)] < 24 mmol/L. BP and insulin resistance, reflected by hemoglobin A1c, were among cardiovascular risk factors. Diet was assessed with food-frequency questionnaires. Linear regression analysis was applied to investigate association between NAE and acidosis and between dietary factors and acidosis.ResultsMean age ± SD was 53 ± 13 years; 57% of patients were male. Acidosis was present in 31% of RTRs. NAE was associated with acidosis (serum HCO(3)(-): β=-0.61; serum pH: β=-0.010; both P<0.001). Patients with high intake of animal protein (i.e., from meat, cheese, and fish) and low intake of fruits and vegetables had significantly lower serum HCO(3)(-) and serum pH. No associations were observed between NAE and cardiovascular risk factors, such as hypertension and insulin resistance.ConclusionsIn addition to conventional factors contributing to acidosis, diet might influence acid-base homeostasis in RTRs. Higher intake of fruits and vegetables and lower animal protein intake is associated with less acidosis in RTRs.

| S-EPMC3488949 | biostudies-literature

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