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G Baverel

Publications and source records attributed to G Baverel.

79 records · Page 5Linked to original sources
PubMed1976

Glutamine synthetase and glutamyltransferase in the kidney of man, dog, and rat.

Glutamine synthetase (GS) is known to exist in the kidney of the rat, guinea pig, rabbit, and sheep but not in that of the dog, pig, cat, or pigeon. No data is available in man. Assay of histologically normal renal tissue obtained in human subjects during surgery for abdominal vascular disease failed to demonstrate significant GS activity. In addition, L-glutamine gamma-glutamyltransferase (GT) activity was also very low. The same results were observed in the dog, in which both GS and GT activities did not exceed 15% of those found in the kidney of the normal rat. In the latter animal both GS and GT activities are higher in the outer medulla (312 and 1,165 mumol/h per g wet wt, respectively) than in the cortex (230 and 844, respectively). During metabolic acidosis, GT activity did not change but GS activity decreased in the outer medulla by 40%. When renal cortex slices from normal rats were incubated in the presence of ammonia, glutamate, and octanoate (as a source of ATP), net synthesis of glutamine was readily demonstrated in contrast to slices from normal DOGS. The present studies demonstrate that the kidney of man, like that of the dog, is devoid of significant glutamine synthetase and glutamine gamma-glutamyltransferase activities. In the rat, we have confirmed the functional significance of GS activity in the kidney. We have also shown that renal GT activity is ammoniagenic in vitro in this animal, but the contribution of this system to total ammonia production in vivo remains to be demonstrated.

Acidosis↗
PubMed1975

Intrarenal distribution of citrate in the dog during antidiuresis and diuresis.

The intrarenal distribution of citrate was evaluated in the dog during antidiuresis and osmotic diuresis, by using the specific citrate assay method of Moellering and Gruber. The measurements were made on tissue samples taken from four different regions throughout the kidney: cortex, outer and inner medulla, and papilla. During antidiuresis, a characteristic distribution of citrate was observed with highest levels in the papilla and lowest ones in the outer medulla. A medullary concentration gradient for citrate was found. Mannitol greatly decreased papillary citrate and sodium, but no changes in outer and inner medullary citrate occured. The results could not be explained by the citrate contained either in the trapped urine or blood in the tissue. It is suggested that citrate accumulation in the inner regions of renal medulla may be accounted for by countercurrent mechanisms or regional differences in renal citrate metabolism.

Animals↗
PubMed1975

[Intrarenal distribution of calcium and magnesium in the dog. Effect of an osmotic diuresis (author's transl)].

1 The determination of Na, Ca, Mg, and K concentrations was performed in four different regions of the dog kidney (cortex, outer medulla, inner medulla, and papilla) during antidiuresis and during an osmotic diuresis. 2 The results show a medullary concentration gradient for calcium. This gradient is much higher than that found for sodium. 3 An inverse concentration gradient from cortex to inner medulla for Mg and K is found. 4 An osmotic diuresis (hypertonic mannitol) decreases the corticomedullary gradient of Na, but does not alter significantly the intrarenal distribution of Ca, Mg and K. 5 These results consistent with an intracellular localization of Mg and K in the renal tissue. It is suggested that the medullary concentration gradient for Ca may be due either to a countercurrent multiplier system similar to that for Na, or to a higher tissular fixation of Ca in the inner medulla and papilla than in the outer medulla and cortex.

Animals↗
PubMed1975

[Calcium and magnesium concentrations of the renal cortex in the rat. Comparison of 3 methods of tissular extraction of the principal cations].

We describe three methods for extraction of main tissular cations : a) dry ashing method; b) wet ashing method with HNO3; c) wet method on fresh tissue with HCIO4. This study allows the determination of tissular concentrations of calcium, magnesium in renal cortex of the Rat. Our findings show : a loss of Na, K cations probably by volatilization with dry ashing method ; inability for K determination when HCIO4 method is used ; tissular concentrations are : 4,7 mEq Ca ; 21,6 mEq Mg per kg of wet tissue (wet ashing method with HNO3) ; recovery percentage for magnesium is above 100 % (as previously shown by other authors) ; the dry ashing method is less suitable for extraction than the two other methods ; both wet methods lead to similar results and to a recovery percentage near 100 %.

Animals↗
PubMedDate not supplied

Substrate uptake and utilization by the kidney of fed and starved rats in vivo.

In order to obtain information (1) on the quantitative contribution of various circulating substrates to renal metabolism and (2) on the relative importance of net luminal and basolateral transport for substrate uptake, we have precisely quantified the renal blood flow, the urinary flow, and the rates of substrate handling by the kidney of anesthetized fed and 72-hour-starved rats. For this, the concentration of twelve metabolites were simultaneously measured in arterial and venous whole blood and plasma as well as in urine of each rat thanks to the use of microassays based on enzymatic cycling. In fed rats, the main potential energy sources were glucose and lactate followed by fatty acids, ketone bodies, citrate and glycerol. Starvation caused a large increase in renal uptake and metabolism of fatty acids, ketone bodies, glutamine and glycerol, and a large inhibition of lactate utilization. The net peritubular uptake of acetoacetate, citrate, glycerol and free fatty acids demonstrated in both nutritional states was increased by starvation only for glycerol and free fatty acids; net peritubular efflux of both beta-hydroxybutyrate and ammonium ions was stimulated whereas that of glutamine was converted into net peritubular uptake by starvation.

Animals↗
PubMedDate not supplied

Relationship between the renal metabolism of glutamine, fatty acids and ketone bodies.

Using renal cortical slices from acidotic and normal dogs we show that fatty acids such as crotonate, octanoate, palmitate and oleate as well as ketone bodies (beta-hydroxybutyrate and acetoacetate) in concentrations ranging from 0.5 to 5.0 mM induce a 30 to 50% decrease in glutamine uptake and ammonia production when glutamine (1 mM) is used as the basic substrate. Glucose production also decreases by 20 to 30%. Glutamate release in the incubation medium is significantly augmented by fatty acids or ketones. When glutamate 5 mM is used as substrate instead of glutamine, glutamate uptake, ammoniagenesis and glucose production are significantly depressed by fatty acids and ketones. Increased glutamate release from glutamine, decreased glutamate uptake and decreased gluconeogenesis from glutamine or glutamate provide evidence that ketone bodies and fatty acids depress the net flux through the glutamate dehydrogenase reaction invovled in glutamine metabolism. This is further supported by the fact that addition of ketones to alpha-ketoglutarate and ammonia stimulates net glutamate synthesis by kidney tubules.

Acidosis, Renal Tubular↗