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A Frick

Publications and source records attributed to A Frick.

At least 55 records · Page 3Linked to original sources
PubMed1985

PTH independent sex difference in renal handling of inorganic phosphate in the rat: effect of oophorectomy.

In order to evaluate the sex difference in the renal handling of inorganic phosphate (Pi) in the rat we performed clearance experiments using intact, thyroparathyroidectomized (TPTX), oophorectomized (OophX) and orchiectomized (OrchX) rats. During stepwise elevation of the Pi concentration in plasma (Pi-titration) to about 6 mmol/l the reabsorptive mechanism of Pi was saturated. The ratio Pi-reabs./GFR in intact males was higher than in females. A significant difference in this parameter was also observed in thyroparathyroidectomized rats: in females this value was 3.47 +/- 0.13, and in males it was 4.54 +/- 0.37 mumol/ml (P less than 0.001). Oophorectomy in the absence of parathyroid hormone (PTH) increased Pi-reabs./GFR from 3.18 +/- 0.36 to 4.12 +/- 0.24 mumol/ml (P less than 0.001); however, orchiectomy did not significantly change the reabsorption of Pi. In conclusion, the present results demonstrate a PTH independent sex difference in the renal handling of inorganic phosphate and are consistent with the hypothesis that estrogens may play a dominant role in this differentiation.

Absorption↗
PubMed1985

[Microassay for blood adenosine deaminase: study of the role of the enzyme in the ammoniagenesis of the blood sample].

A microassay for adenosine deaminase is elaborated. It is based on the colorimetric measurement of small amounts of ammonia raised during adenosine deamination and separated by continuous flow dialysis. The analytical qualities of the microassay are reported. The enzymic activity concentration in whole arterial blood of 30 control subjects is 2.54 +/- 1,68 micro katal/l (mean +/- 2ET). It is slightly lower in venous blood. The values are higher in man than in women. 92 p. cent of the enzymic activity of whole blood are due to the erythrocytes. The distribution of the arterial enzymic activity concentrations is not significantly different in a group of 85 cirrhotic patients when compared to the control group. No tight correlation can be found between blood adenosine deaminase concentrations and either blood ammonia nor shed blood ammoniagenesis. Inhibitors of adenosine deaminase have little effects on the in vitro ammoniagenesis.

Adenosine Deaminase↗
PubMed1984

Reabsorption of inorganic sulfate in the rat kidney: evidence for an adaptive depression of TmSO4 during SO4 loading.

Clearance methods were employed to study reabsorption of inorganic sulfate (SO4) in the rat kidney. During stepwise elevation of the So4 concentration in plasma by sulfate infusions (SO4 titration), the reabsorption of S)4 increased and reached the maximal reabsorptive capacity for inorganic sulfate (TmSO4). During further SO4 loading TMSO4 decreased by about 50%. At the same time GFR was stable, and the decline of the TmSO4 was not due to volume loading during infusion, since in time-controls with Ringer infusion alone the reabsorption of inorganic sulfate was almost unchanged. The decrease of the TmSO4 was also observed in thyroparathyroidectomized animals. It is concluded that the decline of TmSO4 was a result of the SO4 load per se and may be mediated by an unknown adaptive process.

Absorption↗
PubMed1984

Glucocorticoid-induced inhibition of the reabsorption of inorganic phosphate in the proximal tubule in the absence of parathyroid hormone.

Previous studies from this laboratory have demonstrated a phosphaturic response to hydrocortisone. The present micropuncture studies were undertaken to localize this glucocorticoid-induced effect along the nephron. Adult female Sprague-Dawley rats were used and parathyroidectomized 3 h before the micropuncture. The animals were infused with modified Ringer solution (either without or with phosphate). Hydrocortisone increased both the end-proximal transtubular concentration gradient of inorganic phosphate, (TF/P)Pi, and the fractional delivery of Pi at the end of the proximal convolution significantly. The absolute reabsorption of Pi decreased from 95.1 +/- 29.5 (mean +/- SD) to 59.7 +/- 28.2 pmol/min (p less than 0.005) and the absolute reabsorption of Pi/single nephron glomerular filtration rate from 2.34 +/- 0.59 to 1.35 +/- 0.54 pmol/nl (p less than 0.001) during Pi-Ringer infusion. It is concluded that the glucocorticoid-induced phosphaturia is primarily a result of the inhibition of the reabsorption of Pi in the proximal tubule.

Animals↗
PubMed1981

Phosphaturic response of hydrocortisone in the presence and the absence of parathyroid hormone.

The effect of hydrocortisone (HC) on the renal Pi transport in the presence and in the absence of parathyroid hormone (PTH) in the rat was examined using clearance techniques. During constant infusion of PTH in parathyroidectomized (PTX) rats, HC decreased the reabsorption of Pi from 2.84 to 2.33 mumol/min (P less than 0.001), the TmPi from 4.55 to 3.83 mumol/min (P less than 0.001), the reabs. Pi/GFR values from 0.93 to 0.74 (P less than 0.001) and the TmPi/GFR from 1.73 to 1.42 mumol/ml (P less than 0.001). In the absence of PTH, HC diminished the TmPi from 8.36 to 6.58 mumol/min (P less than 0.005) and the TmPi/GFR from 3.36 to 2.51 mumol/ml (P less than 0.001). It is concluded that the phosphaturic response of hydrocortisone may be important in the homeostasis of inorganic phosphate in the body.

Animals↗
PubMed1981

[Not Available].

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Austria↗
PubMed1981

Effect of colectomy upon ammonemia and glutaminemia in rats with stricture of the portal vein.

Current theories on the pathogenesis of hepatic encephalopathy indicate that intestinal bacteria produce cerebral toxins, such as ammonia; colectomy has been proposed in the treatment of chronic portal systemic encephalopathy. This study was undertaken to evaluate the evolution of ammonemia and glutaminemia during a four month period in rats after a colectomy, with and without portal vein stricture. Groups of nine rats were studied: group 1 served as control study, total colectomy was performed on the rats in groups 2 and 3, but a gradual stricture of the portal vein was produced in the rats of group 3 and group 4 that had not had a colectomy. The ammonia levels were stable in groups 1 and 2, 48 +/- 2 milligrams per 100 milliliters; in group 3, ammonia levels rose significantly one week after portal vein stricture, 136 +/- 10, and decreased progressively until the end of the first month, 70 +/- 10, although in group 4 of the ammonia level always remained higher than in this one. The levels of glutamine decreased after colectomy in group 2 and rose markedly in both groups 3 and 4 during the first week but persisted at the same level only in group 4. These data confirm the importance of hepatic clearing of portal blood in ammonia and glutamine metabolism and underline the importance of the colon as the main, but not exclusive, site of splanchnic ammonia and glutamine production. The improvement in hepatic encephalopathy observed after removal of the colon may be due to the reduced output of these two substances.

Ammonia↗
PubMed1980

Proximal tubular reabsorption of inorganic phosphate in adrenalectomized rats.

Micropuncture studies have been performed in adrenalectomized (Adr.X) and sham-adrenalectomized (Sham-Adr.X) rats in order to examine the effects of acute adrenalectomy on the inorganic phosphate (Pi) transport in the convoluted proximal tubule of superficial nephrons under free flow conditions. Adrenalectomy diminished single nephron glomerular filtration rate from 27.0 +/- 12.4 (Sham-Adr.X) to 10.9 +/- 7.1 nl/min (mean +/- S.D., P less than 0.001), increased the inulin ratio (tubular fluid-to-plasma) at the end of the proximal convolution from 2.14 +/- 0.60 (Sham-Adr.X) to 3.62 +/- 1.67 (P less than 0.001) and decreased both the (TF/P)Pi ratio from 0.87 +/- 0.20 (Sham-Adr.X) to 0.46 +/- 0.28 (P less than 0.001) and the fractional delivery of inorganic phosphate onto the loop of Henle from 44 +/- 18 (Sham-Adr.X) to 15 +/- 10% (P less than 0.001). Thus the fractional reabsorption of inorganic phosphate in the convoluted proximal tubule in acutely Adr.X rats was higher than in Sham-Adr.X animals. It is concluded that glucocorticoid hormones play an important role in the regulation of the fractional reabsorption of Pi in the proximal tubule. The mechanism of this regulation is discussed.

Adrenalectomy↗
PubMed1979

Acute effects of hydrocortisone on the reabsorption of inorganic phosphate in normal, adrenalectomized and parathyroidectomized rats.

Clearance studies have been performed in order to examine the acute effects of hydrocortisone on the reabsorption of inorganic phosphage (Pi) in normal, acutely adrenalectomized (Adr. X) and acutely parathyroidectomized (PTX) rats. Hydrocortisone increased the glomerular filtration rates in all groups, normalized the capacity to excrete water in the Adr. X animals, did not change consistently the fractional reabsorption of sodium in all series and diminished the fraction reabsorption of inorganic phosphate in Adr. X rats from 91.4 +/- 6.5 (mean +/- S.D.) to 78.2 +/- 8.5% (P less than 0.001). It is concluded that the decrease of the fractional reabsorption of Pi in the Adr. X animals was rather the result of the increased filtered load than a direct effect of hydrocortisone on the Pi transport.

Adrenal Glands↗
PubMed1979

Semiautomated enzymic microassay for plasma L-alanine.

Plasma L-alanine is deaminated by bacterial alanine-dehydrogenase; the resulting ammonia is dialyzed out and measured by use of a continuous flow phenol-hypochlorite colorimetric microassay. Concentrations in the range of 10-1,000 mumol alanine/l can be determined in a 50-microliter sample. The optimal conditions for the assay are specified. Study of the analytical qualities of the technique shows high specificity, good reproducibility , and a detection limit of 6 mumol/l. Usual values in human plasma from arterial or venous blood are respectively 296 +/- 166 and 376 +/- 214 mumol alanine/l (x +/- 2 SD). The usual values in rats are close to those found in man.

Alanine↗
PubMed1979

An automated microassay for blood ammonia.

A microassay for blood ammonia has been developed. After dilution, blood is dialyzed by a continuous flow procedure, and the ammonium ions in the dialysate are assayed colorimetrically by the hypochlorite-phenol Berthelot reaction. Concentrations from 1 to 400 mumol/l NH+4 can be measured in a 50 mul whole blood sample. Using slight modifications, concentrations up to 800 mumol/l NH+4 can be determined. The precision, accuracy, sensitivity, and specificity of the method have been studied. In man, the usual values (mean +/- 2 SD) found are 27.4 +/- 10.2 mumol/l NH+4 in arterial blood, 20.9 +/- 9.8 mumol/l in venous blood. The usual values in rats and mice are very close to those given for man.

Amino Acids↗
PubMed1979

Effects of biguanides on the intermediate metabolism of glucose in normal and portal-strictured rats.

Phenformin and metformin treatments may be complicated by lactic adidosis. This metabolic complication seems favoured by preexistent hepatic disease. We have therefore compared the metabolic effects of phenformin and metformin on non fasting normal and portal-strictured rats. The latter group is characterized by impaired hepatic passage of these drugs without hepatocellular lesions. Given orally to normal rats over 5 days, phenformin (20 mg/kg/24 h) and metformin (150 mg/kg/24 h) decreased blood glucose levels and increased blood urea and the substrates of gluconeogenesis (alanine, glutamine, lactic and pyruvic acids), effects more apparent with phenformin than metformin. In non-treated portal strictured rats, blood glucose levels were lower and the intermediate metabolites were higher than in noraml rats, suggesting a modification of gluconeogenesis. Treatment of the portal strictured group by phenformin or metformin induced no changes in the studied parameters. This absence of effect of the biguanides in portal strictured rats supports the postulate that, in normal rats, biguanides act principally on hepatic metabolism by reducing gluconeogenesis and that, in the absence of other hepatic damage, the presence of a peri-hepatic shunt, which, by itself, modifies gluconeogenesis, does not further predispose to lactic acidosis during short term administration of biguanides.

Alanine↗
PubMed1978

Maximal reabsorptive capacity for inorganic phosphate (TmPi) in the absence of parathyroid hormone in the rat: decrease of the TmPi during prolonged administration of phosphate and the role of calcium.

Clearance titration studies were performed to examine the maximal reabsorptive capacity for inorganic phosphate (TmPi) in acutely parathyroidectomized (PTX) rats. Under control conditions, the reabsorption of Pi was 6.01 +/- 0.92mumol/min (mean +/- S.D.), and during the administration of phosphate the reabsorption of Pi increased initially to 11.62 +/- 2.20 and decreased finally to 7.97 +/- 2.02mumol/min. The Reabs/GFR values were 2.12 +/- 0.23 (control), 3.57 +/- 0.21 and 2.49 +/- 0.42mumol/ml (experimental), respectively. Thus, the TmPi decreased significantly during phosphate loading. Because this drop of the TmPi was accompanied by a significant decrease of the calcium concentration in plasma in these PTX animals, another series of experiments was performed in which the calcium losses in plasma were replaced. Under these conditions the decrease of the TMPi was significantly smaller than in hypocalcemia. It is concluded that calcium may regulate the renal Pi transport in the absence of parathyroid hormones, at least in hypo- and normocalcemic states.

Animals↗
PubMed1978

Enzymic micro-assay for blood glutamine.

Blood glutamine is hydrolyzed by glutaminase; the resulting ammonia is dialyzed out and measured by use of a continuous-flow colorimetric microassay. Concentrations in the range of 10 to 1300 micromol of glutamine per liter can be determined in a 40-microliter sample. With slight modifications, higher concentrations, up to 5 mmol/liter, can be measured. Assay conditions and the qualities of the microtechnique were made optimal. Usual values obtained with this method for arterial and venous blood in man are, respectively, 443 +/- 140 and 466 +/- 142 micromol/liter (mean +/- 2 SD). Corresponding values for rats are 320 +/- 92 and 340 +/- 108 micromol/liter. Fasting causes a decreased blood glutamine.

Adult↗
PubMed1977

Effect of expansion of extracellular fluid volume on the maximal reabsorptive capacity for inorganic phosphate in parathyroidectomized and intact rats.

Clearance studies were performed in order to examine the effect of expansion of extracellular fluid volume (ECFV) on the maximal reabsorptive capacity for inorganic phosphate (TmPi) in acutely parathyroidectomized (PTX) and intact rats. TmPi values were obtained in both control and volume expansion. In PTX rats, the TmPi values in control and expansion were 8.25 +/- 1.52 and 6.14 +/- 1.02 micronmol/min (mean values +/- S.D.), respectively; the TmPi/GFR values were 2.96 +/- 0.31 and 2.09 +/- 0.30 micronmol/ml, respectively. In intact rats, the TmPi values in control and expansion were 3.56 +/- 0.94 and 2.98 +/- 0.94 micronmol/min, respectively, and the TmPi/GFR values were 1.34 +/- 0.23 and 1.05 +/- 0.23 micronmol/ml, respectively. From these results it is concluded that expansion of ECFV decreases the TmPi values both in the absence and presence of parathyroid hormone.

Absorption↗