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C de Rouffignac

Publications and source records attributed to C de Rouffignac.

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

Modulation by calcitonin of magnesium and calcium urinary excretion in the rat.

We evaluated the effects of human calcitonin (hCT) on electrolyte excretion in hormone-deprived rats, that is, in the absence of endogenous parathyroid hormone, antidiuretic hormone, thyrocalcitonin and glucagon, the effects of which might have interfered with those of exogenous calcitonin. Plasma hCT levels, measured by radioimmunoassay, varied from 0 to 32 ng/ml. In these rats, hCT decreased magnesium (Mg) and calcium (Ca) excretion in a dose-dependent fashion. Maximal decreases were observed for hCT plasma concentrations comprised between 3 and 5 ng/ml, and persisted at the highest doses. Sodium, potassium, water, and total solute excretions were constant in the calcitonin concentration range explored. The same was observed for phosphate, except that slight but significant phosphaturia was elicited by the highest doses. Calcium and phosphate infusions to attenuate the fall in plasma Ca and phosphate concentration subsequent to hCT infusion, did not alter the hormonal effect on Ca and Mg excretion. hCT can therefore directly modulate Mg and Ca reabsorption by the kidney at plasma concentrations within the physiological range. The maximal effects on Mg and Ca reabsorption were obtained at plasma concentrations which are generally reached after maximal stimulation of endogenous calcitonin secretion. It is suggested that in rats, endogenous secretion of calcitonin stimulates Ca and Mg renal reabsorption without modification of sodium and phosphate excretion.

Animals↗
PubMed1985

Urinary concentrating ability: insights from comparative anatomy.

It appears difficult to build a coherent picture of the concentrating system of the mammalian renal medulla. This may be due to the diversity of the factors involved and to considerable interspecies differences. Several morphological adaptations that may be critical in the improvement of water conservation are described. They include variations in the length of the papilla, number of nephrons, percentage of long-looped nephrons, nephron heterogeneity, development of pelvic fornices, confluence of collecting ducts, vascular bundles in the inner stripe of the outer medulla, thin descending limb epithelium, and relative development of the three medullary zones. The organization of the medullary circulation is described; the medulla includes several functionally different compartments favoring preferential exchanges by the juxtaposition of certain tubules and vessels. This may improve the efficiency of certain recycling routes and hence the insulation of the different compartments. As discussed in section III, a better inner medullary insulation may be key, not (or not only) in achieving a high urine concentration but mainly in reducing the time required to reach this high concentration. This overview of the multiple interspecies variations in medullary organization underlines the importance, among other factors, of the inner stripe architecture and of the internephron differences in the process of urine concentration.

Amphibians↗
PubMed1985

Effects of dDAVP on rat juxtamedullary nephrons: stimulation of medullary K recycling.

The effects of 1-desamino-8-D-arginine vasopressin (dDAVP) on the handling of water and electrolytes by the juxtamedullary nephrons were studied on rats with reduced circulating levels of antidiuretic hormone (ADH), parathyroid hormone, calcitonin, and glucagon, all of which stimulate the adenylate cyclase system of the thick ascending limb and the distal tubule. In such hormone-deprived rats and in hormone-deprived + dDAVP rats, the concentration of Na, Cl, and total solutes was lower in the ascending than in the descending limbs, whereas the inulin concentration was similar at both sites. dDAVP did not alter the fraction of NaCl remaining in the thin limbs, but tended to reduce that of Mg and Ca. On the other hand, dDAVP significantly increased the fraction of filtered K remaining from 65.8 +/- 5.2 to 107.3 +/- 15.8%. A direct correlation was observed between the fraction of filtered K remaining at the tip of the juxtamedullary loops and the fractional excretion rate of K in urine. Since dDAVP enhances distal K net secretion, as previously shown in our laboratory, these results indicate that the medullary recycling of K from nephron terminal segments to Henle's loop of juxtamedullary nephrons is stimulated by this peptide.

Animals↗
PubMed1984

Effects of antidiuretic hormone on electrolyte reabsorption and secretion in distal tubules of rat kidney.

The effects of (1-desamino-8-D-arginine) vasopressin (dDAVP) on water and electrolyte transport in the distal tubule were investigated by micropuncture. Since, in addition to antidiuretic hormone, parathyroid hormone, calcitonin and glucagon stimulate the adenylate-cyclase system in this nephron segment, experiments were performed on hormone-deprived rats, i.e. homozygous DI Brattleboro rats with reduced levels of endogenous parathyroid hormone, calcitonin and glucagon. Along the distal tubule, dDAVP enhanced water, Cl, Na and Ca reabsorption and sharply increased net K secretion. Phosphate transport was left unchanged and Mg reabsorption was not significantly altered by dDAVP between the early and late distal tubule. Antidiuretic hormone also slightly increased water filtration rate in the superficial nephron, which rose in proportion to whole kidney glomerular filtration rate. It is concluded that, in rats: antidiuretic hormone stimulates water, NaCl and Ca absorption and enhances K secretion along the distal tubule and the tubular effects of dDAVP on electrolyte transport in the loop and distal tubule are responsible for decreasing Mg and Ca urinary excretion.

Absorption↗
PubMed1984

Fluid composition of basolateral space of kidney cells in culture and its modification by intracellular cAMP.

LLC-PK1 kidney cells, like other epithelial cells, form domes due to Na+ and water movements from the apical to the basolateral side of the epithelium when cultured on a nonpermeable support. The composition of the fluid trapped under these domes can therefore be considered to reflect the nature of the fluid reabsorbed through the epithelium. Collecting the basolateral fluid by micropuncture and analyzing it by electron microprobe revealed that it was isosmotic with the external medium and that the concentrations of Na+, Cl-, Ca2+, Mg2+, and phosphate were nearly the same in both. In contrast, the K+ concentration was found to be 40% lower under the domes than in the bath. Changing the osmolality of the apical medium showed that the epithelium was leaky for water, although it maintained an ionic gradient for at least 20 min. Fifteen minutes after addition of dibutyryl adenosine 3',5'-cyclic monophosphate or 3-isobutyl-1-methylxanthine (5 X 10(-4) M) to the external medium, the phosphate concentration in the basolateral fluid was increased. This rise peaked at 1 h and diminished thereafter. The significance of these observations is discussed in regard to transepithelial permeability and to the transport properties of LLC-PK1 cells.

1-Methyl-3-isobutylxanthine↗
PubMed1984

ADH-like effects of calcitonin on electrolyte transport by Henle's loop of rat kidney.

The effects of physiological doses of human calcitonin (HCT) on renal excretion and tubular transport of water and electrolytes were investigated in hormone-deprived rats, i.e., homozygous DI Brattleboro rats with reduced levels of circulating glucagon, parathyroid hormone, and thyrocalcitonin, as these hormones are believed, together with ADH, to stimulate the same cells of the thick ascending limb. The experimental design was similar to the one used in a preceding study aimed at determining the effects of ADH in hormone-deprived rats [C. de Rouffignac et al. Am. J. Physiol. 244 (Renal Fluid Electrolyte Physiol. 13): F156-F164, 1983]. In the present experiments, HCT consistently increased the reabsorption of Mg, Ca, and K and, to a lesser extent, Na and Cl in the loop of Henle, but phosphate transport did not rise. The urinary excretion rate of Mg and Ca fell significantly. These data are very similar to the findings obtained with ADH on hormone-deprived rats. It is concluded that, in vivo, administration of HCT 1) stimulates reabsorption of Na, Cl, Mg, Ca, and K by the thick ascending limb, and 2) consistently enhances Mg and Ca reabsorption by the whole kidney by enhancing reabsorption in the loop of Henle. The similarity of the physiological responses elicited by ADH and calcitonin on the thick ascending limb supports the hypothesis of multiple hormonal control of electrolyte transport by the thick ascending limb.

Animals↗
PubMed1984

Volume expansion modulates NaHCO3 and NaCl transport in the proximal tubule and Henle's loop.

The effects of extracellular fluid volume expansion on kidney reabsorption of bicarbonate, chloride, and water were examined in Sprague-Dawley rats by paired micropuncture experiments in which tubular fluid was collected from early distal and end-proximal sites. In group I, rats were studied during a plasma-replete euvolemic state and after 10% body wt colloid-free volume expansion. The filtered loads were similar in euvolemia and expansion; expansion increased end-proximal total CO2 concentration ([tCO2] EP) from 13.0 +/- 0.8 to 18.4 +/- 0.7 mM and inhibited the tCO2 fractional reabsorption 26% in the proximal convoluted tubule and 15% in Henle's loop. Early distal tCO2 delivery therefore increased from 61 +/- 7 to 140 +/- 17 pmol X min-1 X g kidney wt-1. A more pronounced inhibition of fractional reabsorption of chloride (45%) and water (35%) occurred in the proximal convoluted tubule during expansion. In group II, rats were studied during 5% body wt 70 g/liter albumin-containing expansion and after 10% body wt colloid-free expansion. Compared with euvolemia of group I, albumin expansion decreased proximal fractional reabsorption of tCO2 13%, chloride 19%, and water 14% without change in filtered loads, and [tCO2]EP rose to 17.2 +/- 0.7 mM. A 10 g/liter decrease in plasma protein concentration during colloid-free expansion was associated, compared with albumin expansion, with inhibition of proximal fractional reabsorption of tCO2 by 4%, chloride by 18%, and water by 9% without further altering [tCO2]EP. We conclude that 1) expansion specifically inhibits bicarbonate reabsorption in the proximal convoluted tubule and in Henle's loop independent of change in filtered load or in peritubular protein concentration, probably by enhancing bicarbonate backdiffusion and reducing proton secretion; 2) expansion-induced decrease in peritubular protein concentration contributes to the proximal expansion effect probably by specifically inhibiting transcellular sodium chloride reabsorption.

Animals↗
PubMed1983

Stimulation by human calcitonin of electrolyte transport in distal tubules of rat kidney.

The effects of human calcitonin (HCT) on the distal tubule were investigated by micropuncture in hormone-deprived rats, i.e. in the absence of parathyroid hormone, antidiuretic hormone and glucagon, which might have masked these effects. Two groups of rats were studied: hormone-deprived and hormone-deprive + HCT, infused at 1.0 mU/min X 100 g.b.w. In the urine, HCT markedly reduced Ca and Mg excretion whereas excretion of water, Na and K was not significantly affected. Along the distal tubule, HCT strongly enhanced Na, Cl, Mg, Ca and total solute reabsorption, decreased K secretion but did not alter water or phosphate transport. It is concluded that HCT stimulated Na, Cl, Ca and Mg reabsorption. If, as suggested, HCT also stimulated the reabsorptive component of K transport, the hormone should therefore elicit the same physiological effects in the distal tubule and the thick ascending limb.

Animals↗
PubMed1983

Stimulation by antidiuretic hormone of electrolyte tubular reabsorption in rat kidney.

The effects of 1-desamino-8-D-arginine vasopressin (dDAVP) on renal excretion and tubular transport of water and electrolytes were investigated in homozygous DI Brattleboro rats. To ascertain these effects on the loop of Henle, circulating glucagon, parathyroid hormone, and thyrocalcitonin were reduced before the experiments, as these hormones are believed to stimulate the same cells of the thick ascending limb as ADH. dDAVP did not alter either glomerular or proximal tubular functions. In the loop, it consistently raised reabsorption of Mg, Ca, K, and, to a lesser extent, Na and Cl, but phosphate transport was not affected. dDAVP lowered the urinary excretion rates for Mg, Ca, K, Cl, and total solutes. For Mg, this reduction was independent of the drop in the urinary flow rate following dDAVP administration but was significantly correlated to this drop in the case of Ca, K, Cl, and total solutes. Na and P excretions were not altered by dDAVP. It is concluded that, in vivo, administration of ADH 1) stimulates reabsorption of Na, Cl, Mg, Ca, and K by the thick ascending limb, 2) consistently enhances Mg reabsorption by the whole kidney by enhancing reabsorption in the loop of Henle, and 3) at maximal antidiuresis, raises Ca, K, Cl, and total solute reabsorption, probably because of the drop in tubular flow rates in the distal parts of the nephron consequent to the hormone administration.

Animals↗
PubMed1983

Developmental pattern of water and electrolyte transport in rat superficial nephrons.

Micropuncture samples were collected from late proximal and early distal sites of the same nephron in nondiuretic young rats aged 13-15, 19-21, and 30-39 days. Plasma ultrafiltrate (UF), tubular fluid (TF), and final urine were analyzed for Cl, Na, K, Mg, P, and Ca concentrations by electron probe. Between days 13 and 39, the proximal convoluted tubule reabsorbed a constant fraction of continuously increasing filtered loads of water, sodium, and potassium. The mean TF/UF concentration ratio for Cl in the late proximal tubule was 0.98 +/- 0.03 in the 13- to 15-day age group and increased to 1.20 +/- 0.03 in the 30- to 39-day age group. The mean TF/UF concentration ratio for Mg increased from 1.17 +/- 0.07 at 13-15 days to 2.07 +/- 0.22 at 30-39 days. The mean TF/UF concentration ratio for Ca at the end of the proximal tubule was found to be significantly lower than unity in the two youngest groups and higher in the oldest. Evidence was also found for maturation of the loop of Henle. The amounts of Cl, Na, K, and Ca reabsorbed by the loop, expressed in percent of the amount delivered, rose significantly with age. In contrast, mean Mg fractional reabsorption was already maximal in the youngest group. Phosphate reabsorption in the loop was limited in all three groups. It is concluded that in the 13- to 15-day rats 1) the fraction of the Na, K, and H2O filtered loads reabsorbed along the proximal tubule is already the same as in adult animals; 2) the proximal tubule epithelium is not able to create or maintain a transepithelial concentration gradient for Cl; and 3) the fractional reabsorption of Mg is higher than in the adult animal. It is also concluded that Cl, Na, K, and Ca transport along the loop of Henle all have the same maturation pattern but that the pattern for Mg is different.

Aging↗
PubMed1983

Effects of calcitonin on the renal concentrating mechanism.

The effects of salmon calcitonin on the renal concentrating mechanism were investigated in homozygous DI Brattleboro rats. The levels of peptide hormones believed to produce the same physiological responses as antidiuretic hormone on the thick ascending limb (glucagon, parathyroid hormone, and calcitonin) and the cortical collecting ducts (calcitonin) were reduced by acute thyroparathyroidectomy and somatostatin administration. In these hormone-deprived animals, the corticomedullary concentration gradient was almost abolished; the (F/P)osmol at the tip of the juxtamedullary nephrons was 1.19 +/- 0.05. Calcitonin administration restored the gradient [(F/P)osmol = 1.85 +/- 0.14] and simultaneously absolute and fractional water excretion fell significantly despite the concomitant rise in the glomerular filtration rate. It is concluded that 1) in the hormone-deprived animal, calcitonin administration consistently enhances the corticomedullary concentration gradient, and 2) the effects of hormone deprivation and calcitonin administration on the urinary concentrating mechanism are compatible with direct stimulation by calcitonin of electrolyte reabsorption along the thick ascending limb and/or of the water permeability of the cortical collecting ducts.

Animals↗
PubMed1982

Flow-correlated influx of K, Ca, P, and Mg during continuous microperfusion of the loop of Henle in the rat.

Investigations on hydropenic rats were undertaken enabling us to determine the relative loop influx rates for potassium, calcium, magnesium, and phosphorus during end proximal continuous microperfusions at 15 or 35 nl . min-1 with saline free of these ions. Replicate quantitative collections were taken at collected flow rates of 9 or 26 nl . min-1. Element concentrations were determined by electron probe analysis. Results showed a significant influx of all four ions in the fluid collected at the early distal site, with magnesium showing the smallest entry rate. As expected, calcium and potassium concentrations at the early distal site increased with the perfusion flow rate. In contrast, phosphorus concentration decreased with flow. Phosphorus concentration at low flow was 0.43 +/- 0.06 mmole . liter-1 vs. 0.25 +/- 0.03 at high flow (P less than 0.01). However, increasing influx was seen with increasing flow for phosphorus (r = 0.58, P less than 0.001). Magnesium concentrations did not significantly change with flow although they were clearly different from zero: 0.12 +/- 0.02 vs. 0.10 +/- 0.02 mmole . liter-1. The rate of magnesium influx as a function of flow was also highly significant (r = 0.48, P less than 0.01). Thus, there is an increase in loop influx in all four ions with high flow rates despite disparate flow influences on early distal concentrations. In conclusion, these experiments demonstrate that (1) magnesium can enter the tubular lumen of the loop when this structure is perfused with a magnesium-free solution and (2) under our experimental conditions, phosphate can also enter the lumen suggesting that the concentration of phosphate at the early distal site is limited by the rate of entry.

Animals↗
PubMed1982

Effect of furosemide on sodium and potassium flow at the end of the juxtamedullary descending limb in Psammomys obesus.

To examine the effect of reducing medullary interstitial solute concentration on sodium and potassium flow at the end of the juxtamedullary descending limb in Psammomys obesus, micropuncture was performed on the exposed left renal papilla. After a control period, furosemide was administered to reduce medullary interstitial solute concentration without altering the delivery of sodium, potassium and water from the proximal tubule. The fraction of filtered sodium remaining at the end-descending limb before (52 +/- 4.9%) and after furosemide (55 +/- 4.2%) was not significantly different, despite a fall in tubule-to-plasma osmolality from 4.32 to 2.00 (p less than 0.001). In contrast, the fraction of filtered potassium delivered to the end-descending limb fell from 92 +/- 9.0% to 61 +/- 8.0% (p less than 0.001). As expected, the fraction of filtered sodium and potassium remaining at the end of the accessible proximal tubule of the superficial nephron was not changed after the administration of furosemide. While these findings do not provide additional support for the thesis of transepithelial sodium addition to the juxtamedullary descending limb, they strongly suggest that transepithelial entry (secretion) of potassium normally occurs upstream to the juxtamedullary hairpin turn of Psammomys obesus.

Animals↗
PubMed1982

X-ray analysis of biological fluids: contribution of microdroplet technique to biology.

Electron probe analysis by x-ray spectrometry is used in biology for simultaneous determination of the concentrations of any elements with a higher atomic number than that of carbon in single samples with volumes of 0.01 to 0.5 nl. In this technique, deposits prepared from identical volumes of biological fluids and standard solutions are totally covered by the electron beam, and the measured x-ray intensities for each element directly compared. The possibility of intensity quantification depends on the thinness of the dried deposits obtainable by various preparatory techniques. Factors affecting the accuracy of the results include droplet stability under the electron beam, the identity of the degree of oxidation of the elements in biological fluids and standards, sample mass thickness, beam voltage, and matrix effects. Minimum detectable concentrations in the 0.05 mmol.l-1 range are now achievable. This technique is the only one applicable in cases where available volumes are too small to determine the concentrations of several elements on the same sample (for instance of Na, Mg, S, P, Cl, K, Ca, Fe and Co), or even to determine the concentration of a single element (e.g. Mg). Although the droplet technique has so far mainly been used in renal physiology, it has also been applied in reproductive and digestive physiology. Isolated cells are analyzed according to the same principle of totally covering the cell by the electron beam. During the last decade, the vast increase in the relevant literature has testified to the contribution of the microdroplet technique to various fields of biology.

Absorption↗
PubMed1981

Renal function and concentrating ability in a desert rodent: the gundi (Ctenodactylus vali).

Clearance and cortical micropuncture experiments were carried out on non diuretic gundis. In this species, the kidney has a long and well developed papilla but, unlike other desert rodents, the vascular organization of the outer medulla is very simple. After withdrawal of water supply for either 24 h or 3 days before the experiments, the urine osmolality was only 1,361 +/- 57, n = 9, before and 1,136 +/- 89 mosmol . kg-1 during anesthesia. The GFR per 100 g B.W.(0.450 ml . min-1) is lower than in the rat studied under similar conditions. With regard to electrolytes the tubular handling of Na, Ca, K and Mg is similar to that observed for another desert rodent, psammomys obesus. For P, massive reabsorption (more than 30% of the filtered load) takes place along the distal convoluted tubule. The relatively poor concentrating ability of the gundi's kidney is not due to a lack of medullary recycling of urea since a net addition of urea to short loops of Henle is observed in this species. Physiological and morphological observations concerning the gundi and other desert rodent species suggest that the vascular bundle development in the outer medulla might affect the renal response to water deprivation.

Animals↗
PubMed1981

Dependence of water movement on sodium transport in kidney proximal tubule: a microperfusion study substituting lithium for sodium.

The relationship between water and sodium movements through the mammalian proximal convoluted tubule was investigated by substituting lithium for sodium. Proximal convoluted rat Kidney tubules were perfused in vivo with a Ringer solution containing 107 meq/liter lithium and 42 meq/liter sodium. Several micropunctures were made along the same nephron, and [3H] inulin, [14C] glucose, 22Na, osmolality, Na, Mg and Cl were determined on each sample. Measurements of 22Na showed that sodium and lithium diffusion rates were practically identical throughout the entire epithelium. A one- for-one exchange of sodium for lithium induced a negative transepithelial net flux of Na from plasma to lumen. However, despite this negative flux, a positive net water movement was measured from lumen to plasma. This movement was proportional both to glucose reabsorption and to the rise in the chloride concentration, two mechanisms known to be dependent on the transcellular movement of sodium. It was therefore concluded that the net water flux was a function of the unidirectional transcellular net flux of Na. Rabbit proximal convoluted tubules were perfused in vitro with solution containing 75 meq/liter Li and 75 meq/liter Na on both the luminal and peritubular sides. Under these conditions, the water reabsorption rate dropped to half its control value. Water movement was therefore a function of the external sodium concentration, which in turn probably regulates the intracellular Na concentration.

Animals↗
PubMed1981

Distribution of ferrocyanide along the proximal tubular lumen of the rat kidney: its implications upon hydrodynamics.

1. Simultaneous determination of the single nephron glomerular filtration rate (s.n.g.f.r.) and the amount of [14C]ferrocyanide contained per unit length (Fe/mm) of the proximal tubule makes it possible to calculate the tubular radius and flow velocity along this structure. These measurements were made in normal rats, chronically salt-loaded rats, and rats rendered hypotensive by controlled haemorrhage or aortic constriction. 2. In normal rats, Fe/mm remains constant along the proximal tubule, indicating a gradual decrease in tubular radius and constant flow velocity. 3. In salt-loaded rats, with high s.n.g.f.r.s, Fe/mm also remains constant along the proximal tubule, but at a higher level than in normal rats. This indicates larger tubular radii, but the same evolutionary pattern for tubular radius and flow velocity along the proximal tubule, as in normal rats. 4. In rats with controlled haemorrhage, Fe/mm values are low but rise slightly along the proximal tubule. Tubular radius is reduced, and again, gradually decreases along the length. Considering the very low s.n.g.f.r.s, this implies that a large drop in reabsorption along the proximal tubule accompanies the reduction in s.n.g.f.r. 5. In rats with aortic construction, Fe/mm exhibits a large increase along the proximal tubule, suggesting a huge Fe concentration along the tubule, which in turn would indicate that water reabsorption may not diminish in proportion to the reduction in s.n.g.f.r. In some cases, this disruption of the glomerulo-tubular balance led to the cessation of tubular flow in the proximal tubule. 6. In all cases, Fe/mm and the calculated radius in the initial portion of the proximal tubule were correlated to the s.n.g.f.r., suggesting passive adaptation of tubular radius to fluid delivery.

Animals↗