The effects of fluoroacetate, malonate and acid-base balance on the renal disposal of citrate

Renal stone risk factors in patients with type IV renal tubular acidosis

Renal stone formation is uncommon in patients with type IV renal tubular acidosis (RTA). This study was undertaken to explore the urinary biochemical and physicochemical factors in patients with type IV RTA in order to elucidate the mechanisms that protect them from renal stone formation. Twelve subjects with type IV RTA and 12 matched subjects with a similar degree of kidney impairment but without RTA were studied. Both groups of patients had low urinary excretion of calcium, phosphorus, uric acid, and citrate, probably reflective of kidney impairment. Patients with type IV RTA had a significantly lower urinary pH and urinary excretion of calcium than their matched controls. Hypocitraturia was present in both groups without any significant difference between them. This study suggests that the major protection from renal stone formation in type IV RTA results from impaired renal function and ensuing reduction in renal excretion of stone-forming substances, such as calcium and uric acid.

The behaviour of uranium-233 oxide and uranyl-233 nitrate in rats

233UO2 and 233UO2(NO3)2 in aqueous suspension have been administered to rats by pulmonary intubation. The 233U associated with the fraction of the 233UO2 less than 4 nm in diameter translocates from lungs to blood at the same rapid rate as 233U from 233UO2(NO3)2. Identical reactions with blood plasma and lung fluid were observed whether the 233U was administered as less than 4 nm 233UO2 particles or 233UO2(NO3)2. It is suggested that oxidation of UO2 to UO3 occurs followed by the formation of uranyl ion. In blood plasma, approximately 50 per cent of the 233U is bound to transferrin, 25 per cent to citrate and 25 per cent on bicarbonate.

Effect of acidosis, alkalosis and monofluoroacetate administration on citrate and ATP content of rat renal medulla and papilla

1. --Renal distribution of citrate showed that there is an increase in citrate content from cortex to medulla and a decrease from medulla to papilla. Alkalosis produced an increase in citrate content and acidosis a decrease in renal citrate content, in each of the studied renal area. Monofluoroacetate produced no significant change in citrate content of medulla or papilla; it did not interfere with the acido-basic related changes in cortex citrate content, but its effect was additive. 2. --Renal distribution of ATP significantly decreased from cortex to medulla and from medulla to papilla. Acid or basic diet had no influence on intratissular ATP content. Fluoroacetate decreased renal ATP content.

Urinary dicarboxylic acids in patients receiving lithium or rubidium salts

Lithium salts administered in therapeutic doses to four subjects who were kept on controlled diets increased up to fivefold the urinary output of some dicarboxylic acids. Some of the acids affected are intermediates in the tricarboxylic acid cycle, others are chemically similar but not directly related in metabolic terms. This is probably a direct effect on renal transport. Rubidium salts increased urinary 2-oxoglutarate output and blood 2-oxoglutarate levels, probably by some action on intermediary metabolism.

Light and electron microscopic studies of the rat kidney after administration of inhibitors of the citric acid cycle in vivo. I. Effects of sodium fluoroacetate on the proximal convoluted tubule

Light and electron microscopic studies of morphologic changes in the rat proximal convoluted tubule after intraperitoneal injection of sodium fluoroacetate (FAc), 60, 20 and 3.5 mg/kg body weight, have been made. Particular attention was directed toward appreciating different changes in the first (S(1)) and second (S(2)) segments of the proximal tubule. The earliest change was loss of mitochondrial granules and pallor of the mitochondrial matrix, not necessarily associated with matrix swelling. Matrix swelling was greatest at 3 hours after 3.5 mg/kg and was reversible. However, the mitochondria retained their elongate shape and cristae persisted. At 48 hours, some mitochondria appeared normal; in others, abnormal matrix densities of unknown nature were present. Mitochondrial changes were similar in S(1) and S(2) at all times. Enlarged apical vacuoles, most pronounced in S(1), occurred in all rats after 20 mg/kg. The change was uncommon after 3.5 mg/kg. The hypothesis proposed is that vacuoles arise during an FAc-induced hyperglycemic phase, when pinocytotic activity is maintained but the normal pathway of glucose catabolism is inhibited. Moderate dilatation of the rough-surfaced endoplasmic reticulum occurred during the first 2-hour period in S(1) and S(2) tubules after high and low doses, but between 6 and 24 hours, dilatation was extensive in S(1) tubules after 3.5 mg/kg. This change was reversible. Two types of abnormal vacuolar bodies, large and small, have been described, and were unique to S(1) tubules. Acid phosphatase activity was demonstrated in a proportion of the small ones, indiciating that they were a type of lysosome. The larger ones shared features in common with cytosomes of control cells, but acid phosphatase activity was not demonstrated in them and their origins and functions remain obscure. The biochemical lesions induced by fluoroacetate have been discussed and a tentative interpretation of some of the morphologic changes has ben made.

Regulation of renal citrate metabolism by bicarbonate ion and pH: observations in tissue slices and mitochondria

The effect of acid-base balance on the oxidation and utilization of citrate and other organic acids has been studied in tissue slices and isolated kidney mitochondria. The results show that: 1) With bicarbonate-buffered media, citrate oxidation and utilization are inhibited in slices of renal cortex and in kidney mitochondria when [HCO(3) (-)] and pH are increased within the physiologic range (pH 7.0 to 7.8; 10 to 60 mumoles HCO(3) (-) per ml). When phosphate or Tris buffers are used, no comparable effect on citrate oxidation occurs when pH is varied. 2) This effect is not demonstrable in heart or liver slices when a physiologic buffer is used. 3) alpha-Ketoglutarate utilization is inhibited in slices of renal cortex under similar conditions. Pyruvate and L-malate utilization are not inhibited in slices or mitochondria. 4) Citrate content in slices of renal cortex incubated with a high [HCO(3) (-)] is considerably greater than the concentration found with a low [HCO(3) (-)] in the medium. This effect is not duplicated by pH change in a nonbicarbonate buffer system. In mitochondria citrate content is also increased markedly at high bicarbonate concentrations. 5) The kinetic characteristics of the inhibition of citrate oxidation are those of a competitive type of inhibition. 6) When pH was varied with a constant [HCO(3) (-)] in the media, citrate oxidation was inhibited by increasing pH in slices of renal cortex but not in mitochondria. On the other hand, when [HCO(3) (-)] was increased without change in pH, no decrease in citrate oxidation occurred in slices, but a marked inhibitory effect was found when mitochondria were used. From a comparison of these results with those previously obtained in intact animal experiments, we conclude that the inhibition of citrate oxidation caused by increasing pH and [HCO(3) (-)] in slices of renal cortex and kidney mitochondria is an in vitro representation of the inhibition of citrate reabsorption in the nephron that occurs in metabolic alkalosis. Thus, citrate clearance increases in metabolic alkalosis because of inhibition of oxidation of reabsorbed citrate within cells of the renal tubules. This inhibition is the result of an inhibitory effect of bicarbonate ion on citrate oxidation in mitochondria.