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C de Rouffignac

Publications and source records attributed to C de Rouffignac.

At least 73 records · Page 4Linked to original sources
PubMed1980

Phosphate reabsorption in juxtamedullary nephron terminal segments.

Adult Munich Wistar rats undergoing mild salt diuresis (NaCl 20 g x l-1, 0.1 ml x min-1) were injected with tracer doses of 3H-Inulin and 32P-sodium phosphate in thin descending and ascending limbs of Henle's loop, collecting ducts accessible at the surface of the papilla and early distal superficial tubules. Kidneys were prepared for simultaneous papillar microinjection and urinary flow collection. Expressed in percent of the amounts injected, unidirectional phosphate reabsorption fluxes were 5 +/- 1% and 3 +/- 1% for injections into early distal superficial tubules and collecting ducts, respectively. By contrast, the flux was 21.7 +/- 3% for injections into either the descending or ascending thin limbs of juxtamedullary nephrons. We conclude from these results that in the rat, a significant amount of phosphate is reabsorbed by the juxtamedullary distal tubules and/or the subsequent arcades connecting the juxtamedullary distal tubules to the collecting ducts.

Animals↗
PubMed1980

Renin uptake by the right kidney in the rat following partial clamping of the left renal artery.

Renin secretion from both kidneys was studied in eleven Wistar rats for 40 min after partial clamping of the left renal artery. 14C Inulin and 3H para aminohippuric acid clearance and the arterial and venous plasma renin concentrations were measured in each kidney during control and experimental procedures. After clamping, the arterial plasma renin concentration increased and correlated positively with the plasma renin concentration in both renal veins. However, the plasma renin concentration of the right renal vein was lower than the arterial concentration (P < 0.01). The slope correlating the two variables is significantly lower than unity (P < 0.05, n = 19). As the left kidney secreted a large amount of renin, calculation of secretion by the right kidney decreased to negative values, implying renin uptake by this kidney. These data suggest the existence of a balance between the two kidneys. Renin secretion appears to maintain an equilibrium between release by the juxtaglomerular apparatus and removal from the blood into interstitial space. Release seems to predominate in the hypoperfused kidney, and removal in the contralateral kidney. This may result from the increase of the circulating angiotensin II, since we observed a direct correlation between renin uptake and the arterial plasma renin concentration.

Animals↗
PubMed1980

Stimulation of renal magnesium reabsorption by calcitonin in the rat.

The effect of salmon synthetic calcitonin (CT) on the renal excretion of water and electrolytes was investigated in thyroparathyroidectomized (TPTX) nondiuretic rats. CT did not significantly alter the excretion of either H2O, Na, Ca, phosphate (P), or K, but consistently decreased both fractional and absolute excretion rates of Mg. This latter effect was probably the result of enhanced reabsorption by the loop of Henle. The excretion rates of P and K were either increased or decreased by CT administration; the Mg response on both the whole kidney and loop of Henle was always observed, however, irrespective of the P and K response. In other experiments, the decrease in Mg excretion was still observed when the fall in the filtered load of P and Ca secondary to CT administration was prevented by an appropriate infusion of Ca and P. It is concluded that 1) CT can alter K and P excretion rates but this influence can be prevented by maintaining the filtered load of Ca and P constant, and 2) CT exerts a marked stimulatory effect on Mg reabsorption, presumably by enhancing reabsorption by the thick ascending limb.

Animals↗
PubMed1979

Urinary concentrating mechanism in the desert rodent Psammomys obesus.

The mechanism by which osmolality rises in fluid in the juxtamedullary descending limb was examined in Psammomys obesus by micropuncture of the left renal papilla. The concentration of Na, Cl, K, Mg, and phosphorus was determined by electron probe; Cl concentration by both probe and the microcoulometric technique of Ramsay et al. (J. Exp. Biol. 32: 822--829, 1955). The mean urine-to-plasma ultrafiltrate (U/P) osmolality was 5.5 +/- 0.46 (SE). In 43 samples obtained from the end-descending limb in 16 animals, mean values were: tubule fluid-to-plasma ultrafiltrate (TF/P) osmolality, 3.64 +/- 0.30; (TF/P)In, 6.96 +/- 0.52; (TF/P)Na, 3.53 +/- 0.27; (TF/P)Cl-e, 4.11 +/- 0.37 (-e is electron probe determination); and (TF/P)Cl-r, 4.25 +/- 0.37 (-r is determination by method of Ramsay). In terms of percentage of filtered ion remaining at the end-descending limb, Na was 54 +/- 3.7%, Cl-e was 61 +/- 3.6%, and Cl-r was 63 +/- 4.0%. The percentage of filtered chloride remaining averaged 80% or more in three animals, equalled or slightly exceeded 100% in six individual descending limb samples, and in all animals was a function of loop fluid osmolality (y = 8.61x + 31.9, r = 0.66, P less than 0.01). The results are most consistent with the thesis that both water extraction and transepithelial NaCl addition contribute to the rise in osmolality of fluid in the descending limb of the Psammomys.

Animals↗
PubMed1978

Glucose-mediated inhibition of phosphate reabsorption in rat kidney.

Clearance, tracer intra-arterial injection, and tracer intratubular microinjection techniques were used on two strains of Wistar rats. In Saclay rats, clearance studies during hyperphosphatemia showed that glucose significantly decreased reabsorption of phosphate; during normal phosphatemia, glucose induced a 25% inhibition both in nondiuretic and in volume-expanded animals; thyroparathyroidectomy did not modify this inhibition. When mannitol was substituted for glucose, no change in phosphate reabsorption was noted. Tracer injection into the renal arteries of [3H]inulin, [14C]glucose, and [32P]-phosphate with or without additional unlabeled glucose or mannitol showed that the presence of glucose significantly increased 14C and 32P urinary recoveries but not mannitol. Intratubular paired microinjections into early proximal tubules of the same tracers with and without glucose showed that addition of sugar also increased the 14C and 32P urinary recoveries. In Munich rats, the effects were much less marked than in Saclay rats. It is concluded that the inhibitory effect of glucose 1) partly results from intrarenal factors, 2) is linked to glucose reabsorption per se but not to a nonspecific osmotic intraluminal effect, 3) is localized on the tubular luminal side, and 4) is subject to strain differences.

Animals↗
PubMed1977

Renal clearance studies in fetal and young guinea pigs: effect of salt loading.

The maturation of renal function was investigated by clearance studies in 11 fetal, 9 young, and 4 adult guinea pigs undergoing salt loading (NaCl 1.5%, 75 mul min-1 100 g-1) and in 10 young and 4 adult animals under nondiuretic conditions. The fetal preparation described makes it possible to obtain two to four steady clearance periods for each animal. In the fetus, GFR increased significantly with age, but less than in the newborn. Fractional water and sodium reabsorption was generally low, and net renal secretion of potassium was observed in some cases. Fetal urine was sometimes slightly hypertonic. The effectiveness of the diuretic and natriuretic response following saline expansion was smaller in young than adult animals. The fractional excretion rate of solutes and water increased as a function of age in the young animal and the urinary Na/K concentration ratio showed a marked drop around birth. This latter observation suggests that during the first days of life the effect of saline expansion on the proximal tubule is partially blunted by enhanced sodium reabsorption from the distal nephron due to the high concentration of circulating aldosterone.

Animals↗
PubMed1976

Role of sodium and urea in the renal concentrating mechanism in Psammomys obesus.

Micropunctures were performed at the tip of Henle's loops and vasa recta accessible at the extrarenal surface of the papilla in a desert rodent (Psammomys obesus) studied under mild NaCl ((NaCl 4%, 0.0375 ml/min) and mild urea (urea 4%, 0.0375 ml/min) loading conditions. In Nacl loaded animals, it was confirmed that solute addition (mainly sodium) contributes in a large proportion to the concentrating process along the thin descending limb. Comparison of sodium and urea concentrations in the loops with those in vasa recta at the same level of the papilla demonstrated that 1. the transepithelial sodium gradient was compatible with a diffusion transport of this ion from the interstitium to the thin descending limb; 2. the sodium concentration higher in interstitium than in the loop fluid was not compatible with the existence of a purely passive concentrating process in inner medulla as was recently proposed [8], 3. the transepithelial urea gradient was very limited which indicates that this solute does not play an important part in the concentrating process. In urea loaded psammomys, solute addition (mainly urea) to the thin descending limb fluid was still present but water abstraction was enhanced as compared to salt loaded animals, probably on account to the higher interstitial urea concentration. It is, thus, brought to evidence that the relative contribution of water abstraction and solute addition to the concentrating process along the thin descending limb can vary in a given species as a function of the physiological state.

Animals↗
PubMed1976

Functional and morphologic maturation of superficial and juxtamedullary nephrons in the rat.

The development of single nephron glomerular filtration rate (SNGFER) was studied in both superficial and juxtamedullary nephrons in rats in relation to concomitant morphologic maturation. These experiments were carried out in rats between 23 and 91 days of age (between 36 nad 275 g body weight) with the [14C]ferrocyanide infusion technique. 2. SNGFR of the superficial and juxtamedullary nephrons increased with body weight, glomerular volume and proximal tubular length. 3. The ratio SNGFR of the superficial (S) nephrons/SNGFR of the juxtamedullary (JM) nephrons rose from 0-60 in the 40-60 g rats to 0-84 in the adult rats, demonstrating the centrifugal functional maturation of the nephrons. 4. The S/JM ratio for both glomerular volume and tubular length was constant and averaged 0-72+/--0-12 and 0-81+/-0-05, respectively, indicating that while the increase in SNGFR was greater for S than for JM nephrons, this was not accompanied by concomitant disproportionate increases of glomerular volume and/or proximal tubular length between these nephron categories during development in the rat.

Age Factors↗
PubMed1975

The structural organization of the kidney of the desert rodent Psammomys obesus.

The architecture of the desert rodent Psammomys obesus has been studied by means of standard histologic procedures and by single nephron injections. As other rodent kidneys (rat, mouse), the Psammomys kidney consists of two types of nephrons, 66% short looped and 34% long looped nephrons. The cortex is composed of 4 to 5 layers of glomeruli, which lie closely put together, the glomeruli often touch each other. The superficial and the midcortical glomeruli give rise to short looped neophrons, the juxtamedullary to long looped nephrons. In the strongly developed medulla the inner stripe shows the most striking pattern. It consists of two distinct compartments, that of the giant vascular bundles and that of the interbundle regions. The giant vascular bundles consist of about 8 to 14% arterial vasa recta and 39 to 47% venous vasa recta; furthermore they include the thin descending limbs of the short loops of Henle which amount to 44 to 51% of the bundle structures. The tubules of the interbundle regions surround the bundles in a regular pattern. The inner zone is almost completely surrounded by the renal pelvis; the long broad papilla protrudes into the ureter. The thin descending limbs of short looped nephrons traverse the inner stripe inside the giant vascular bundles. Leaving the bundles they turn back within the inner stripe; their ascending limbs lie in the interbundle region. Both limbs of the long loops of Henle run in the interbundle region, together with the ascending limbs of the short loops and the collecting ducts. The long loops penetrate deeply the inner zone. Many bends are found near the tip of the papilla. The renal pelvis has a very specialized form. It penetrates the inner stripe with many complexely shaped extensions, which surround the giant vascular bundles. Large parts of the bundles with their thin walled structures are thus separated from the pelvic urine only by a single layer of cuboidal epithelium. The possible functional importance of the described specializations of the Psammomys kidney (giant vascular bundles, large inner zone, special shape of the renal pelvis) for the urine concentrating and urea recyclng mechanisms is discussed.

Animals↗
PubMed1975

Glomerular filtration rate and microsphere distributions in single nephron of rat kidney.

In control non diuretic (ND) and in salt-loaded (SL) rats, both the microsphere technique and the 14C ferrocyanide infusion technique were used to determine the distribution of microspheres in single glomeruli and the SNGFR of the corresponding nephrons. A sample of microspheres with a diameter averaging 11.0 +/- 2.6 mu SD was selected from a 15 +/- 5 mu unlabelled batch. In each rat, three million of these microspheres were injected through the left carotid artery. The microspheres were directly counted under microscopic observation in the glomeruli of the nephrons which were microdissected to determine the SNGFR value. The number of microspheres per glomerulus for a given kidney generally varied from 0 to 8 and was independent to the SNGFR value. The diameter of the microspheres trapped was constant in all the animals. The mean number of microspheres for superificial (S) and juxtamedullary (JM) nephrons was, (ND); S = 1.99 +/- 0.48 SE., n = 5; JM = 3.02 +/- 0.51 SE, n = 5; P less than 0.02, (SL): S = 3.75 +/- 0.53 SE, n = 6; JM = 2.86 +/- 0.33 SE, n = 6; P less than 0.05. This distribution was directly related to that of SNGFR in ND rats (S = 39.0 +/- 6.1 SD and JM = 49.5 +/- 10.3 nl/min) but not in SL rats (S = 50.9 +/- 6.1 and JM = 66.9 +/- 10.0 nl/min). In conclusion, the microsphere technique described in the present paper, appears more suitable for investigating single glomerular blood flow since the number and the size of the microspheres trapped are directly determined at the level of the glomerulus.

Animals↗
PubMed1975

Renal phosphate transport: inhomogeneity of local proximal transport rates and sodium dependence.

The standing droplet method has been used in combination with the peritibular perfusion of blood capillaries to determine the build up of transtubular concentration differences of phosphate (Piota) in the renal proximal convoluted tubule of parathyroidectomized rats. Electron probe analysis was used to estimate Piota. At zero time both the intraluminal and the contraluminal Piota concentration was 2 mM. The time dependent decrease of the intraluminal Piota concentration was approximately 4 times faster in the early than in the late proximal convoluted tubule. After 45 sec an intraluminal steady state concentration of 0.20 mM Piota was achieved in the early part. In the late part the intraluminal Piota concentration approached a steady statevalue of 0.54 mM at 123 sec. When sodium free solutions were used the intaluminal Piota concentration increased to 2.22 mM in the earlier and to 2.76 mM in the late part. The data indicate that in the proximal convoluted tubule 1. the rate of phosphate reabsorption is greater in the early part than in the later part, and 2. phospate reabsorption might occur as co-transport with Na+ ions.

Animals↗