N. G. De Santo

Bicarbonate transport along the loop of Henle. II. Effects of acid-base, dietary, and neurohumoral determinants.

The loop of Henle contributes to renal acidification by reabsorbing about 15% of filtered bicarbonate. To study the effects on loop of Henle bicarbonate transport (JHCO3) of acid-base disturbances and of several factors known to modulate sodium transport, these in vivo microperfusion studies were carried out in rats during: (a) acute and chronic metabolic acidosis, (b) acute and chronic (hypokalemic) metabolic alkalosis, (c) a control sodium diet, (d) a high-sodium diet, (e) angiotensin II (AII) intravenous infusion, (f) simultaneously intravenous infusion of both AII and the AT1 receptor antagonist DuP 753, (g) acute ipsilateral mechanicochemical renal denervation. Acute and chronic metabolic acidosis increased JHCO3; acute metabolic alkalosis significantly reduced JHCO3, whereas chronic hypokalemic alkalosis did not alter JHCO3. Bicarbonate transport increased in animals on a high-sodium intake and following AII administration, and the latter was inhibited by the AII (AT1) receptor antagonist DuP 753; acute renal denervation lowered bicarbonate transport. These data indicate that bicarbonate reabsorption along the loop of Henle in vivo is closely linked to systemic acid-base status and to several factors known to modulate sodium transport.

UTILISATION OF KETOACID ANALOGUES OF VALINE AND PHENYLALANINE IN HEALTH AND URÆMIA

Abstract 15 N-labelled ammonium chloride was given to four healthy individuals and to two uraemic patients during studies of the ability of α-ketoisovaleric and β-phenylpyruvic acid to substitute for valine and phenylalanine. 15 N enrichment of valine, phenylalanine, and other essential and non-essential aminoacids is reported, In three of the four healthy individuals the incorporation of 15 N into the appropriate essential aminoacid increased. No significant uptake of 15 N was found in the fourth individual. One uraemic patient showed a much greater enrichment of phenylalanine and valine than did healthy individuals. Her uptake of 15 N was also much greater than the uptake by the other and more uraemic patient who had failed to maintain nitrogen balance with the ketoacids. It is concluded from these isotopic studies that a number of healthy and uraemic men can synthesise phenylalanine and valine from their ketoacid analogues.

The Renal Hemodynamic Response following a Meat Meal in Children with Chronic Renal Failure and in Healthy Controls

The renal hemodynamic response to a meat meal (2 g/kg BW) was studied in 11 healthy children and in 10 children with a mean plasma creatinine concentration of 2.6 +/- 0.1 mg/dl due to chronic renal failure (CRF) of various etiologies. In the healthy status, after a meat meal, the glomerular filtration rate (GFR) increased significantly from a baseline value of 119.0 +/- 5.0 to a peak of 159 +/- 5.8 ml/min x 1.73 m2; in CRF baseline GFR averaged 49 +/- 4.0 and at peak 76.6 +/- 7.2 ml/min x 1.73 m2 (p less than 0.005). The peak GFR response was reached earlier in healthy subjects than in CRF (p less than 0.05) and did not correlate with age or with baseline GFR. Renal plasma flow (RPF) in healthy controls increased from 532 +/- 32 at baseline to 646 +/- 42.9 ml/min x 1.73 m2 after the meal (p less than 0.005). Also in CRF after a meat meal there was a significant increase in RPF from 278 +/- 51 to 65 +/- 66 ml/min x 1.73 m2 (p less than 0.005). The filtration fraction was not affected. The percent increase over baseline values of GFR and RPF at the peak was significantly higher in diseased children. Renal reserve averaged 28.1 +/- 5.3 ml/min in diseased children and 39.7 +/- 5.2 ml/min (p less than 0.01). The data indicate that (1) a meat meal is a suitable method to recruit renal reserve in normal children and in children with chronic renal failure, and (2) the renal reserve is normal in chronic renal failure.

Lysine in Treatment of Hyperornithinemia

A metabolic study in a case of hyperornithinemia with gyrate atrophy of choroid and retina is presented. It is demonstrated that the lysine-ornithine antagonism is a physiological, safe, easy to handle therapeutic tool in hyperornithinemia. A lysine load was invariably associated with a reduction of plasma ornithine concentration. This happened at any level of protein intake. It was also shown that diets containing a low protein intake are invariably associated with negative nitrogen balance.

Tubular Function by Lithium Clearance, Plasma Amino Acids and Hormones following a Meat Meal in Childhood

Tubular function was measured by lithium clearance (CLi) and by its derived formulae before and after the transient increase (lasting 90 min) in glomerular filtration rate (GFR) following a meat meal (2g protein/kg body weight) in 12 normal children. Three baseline and 4 clearances after the meal were obtained, each lasting 30 min. The mean baseline CLi was 23.1 +/- 1.64 ml/min/1.73 m2. At peak GFR response (60 min from starting the meal), CLi averaged 27.6 +/- 2.4 ml/min/1.73 m2 (p less than 0.025 vs. baseline) and it was further increased (32.2 +/- 5.04 ml/min/1.73 m2, p less than 0.01 vs. baseline) 120 min after starting the meal, while GFR returned to baseline values. Fractional lithium excretion averaged 0.23 +/- 0.04 at baseline and increased continuously after the meat meal and, at completion of the study, it averaged 0.38 +/- 0.07 (p less than 0.025 vs. baseline). The distal absolute and fractional sodium reabsorption increased throughout the studies following the meal and peaked at 120 min. The functional changes were associated with a statistically significant increase in the plasma concentration of insulin, glucagon, and total amino acids after the meal. The latter at the end of the study was almost doubled (5,600 +/- 780 versus 3,200 microM at baseline, p less than 0.01). The data indicate that the tubulo glomerular feedback mechanism operates normally after a meat meal. The finding on increased distal sodium reabsorption might point to the existence of an insulin-dependent mechanism.

Histidine for treatment of uraemic anaemia.

A group of 28 uraemic patients on dialysis treatment were given daily supplements of histidine by mouth. Plasma amino-acid concentration, plasma iron, serum transferrin, packed cell volume, and reticulocyte count were all measured before and after two months of histidine supplementation. The treatment raised the plasma histidine concentration and at the same time there was a rise in transferrin and iron levels and packed cell volume. Reticulocyte counts fell after two months of histidine supplementation.

Brain-gut peptides and the renal hemodynamic response to an oral protein load : a study of gastrin, bombesin, and glucagon in man

With the aim of disclosing a possibility for gastrin and bombesin to participate in the postprandial regulation of the renal hemodynamic response, 10 healthy males were studied before and after a meat meal (2 g/kg BW of proteins as cooked red meat). We evaluated the time course changes of glomerular filtration rate (GFR) renal plasma flow (RPF), and the plasma concentrations of gastrin, bombesin, glucagon, and total amino acids. After the meat meal a significant increase in GFR and RPF was seen, within 30 min, along with an increase in plasma gastrin and glucagon. Bombesin and amino acid concentrations increased at a later time. The data suggest but cannot demonstrate a causal role for gastrin and glucagon in the genesis of the hyperfiltration response to acute protein administration.

Haematoma of rectus abdominis associated with dialysis.

Colonoscopy subjects the patient to inconvenience and some discomfort. It is time-consuming for the operators and occupies x-ray facilities for long periods, though we estimate that even in the most difficult cases we have used under 45 seconds of screening time. The instrument is costly, requires careful maintenance, and is subject to wear and tear which may lead to damage of the fibre bundle or of the mechanical parts. For these reasons it seems likely that colonoscopy will be a specialist service provided in a few centres. Examination of the whole colon is not to be recommended as an occasional procedure for those with a limited interest in endoscopy. We wish to thank Sister B. Quaid for her skill in preparing the patients and are indebted to Dr. A. C. Young, Mr. A. G. Parks, and Dr. J. E. Lennard-Jones for their advice and support.

The effect of acute metabolic alkalosis on bicarbonate transport along the loop of Henle. The role of active transport processes and passive paracellular backflux

AbstractThe loop of Henle (LOH) reabsorbs approximately 15% of filtered HCO3− via a luminal Na+-H+ exchanger and H+ATPase. During acute metabolic alkalosis (AMA) induced by i.v. HCO3− infusion, we have observed previously inhibition of LOH net HCO3− reabsorption