PubMed Health⌕ Search

Biomedical subjects

P Houillier

Publications and source records attributed to P Houillier.

At least 19 recordsLinked to original sources
PubMed1998

[Hypercalciuria].

Hypercalciuria is a very frequent disorder that is defined by a daily calcium excretion rate in excess of 0.1 mmol/kg. Whatever its mechanism, it always expresses an increased input of calcium in extracellular fluid, from intestine and (or) bone. In few instances, hypercalciuria is secondary to an underlying disease that needs to be identified (primary hyperparathyroidism, cancer, granulomatosis...). However, in most cases, it is a primary (idiopathic) disorder that reveals an abnormal handling of calcium by intestinal and renal tubular epithelia. It is then treated by a restricted dietary supply in sodium and animal proteins, and by the use of thiazide diuretics.

Absorption↗
PubMed1997

[Extraparathyroid hypercalcemias. Physiopathological and therapeutic aspects].

An increase in plasma calcium concentration is always the consequence of at least one of the following events: an increase in the net calcium input in extracellular fluid, a decrease in glomerular filtration rate, and an increase in the tubular reabsorption of the filtered calcium. In parathyroid hormone-related hypercalcemia, that is typically stable with time, the main determinant is the rise in parathyroid hormone-induced tubular calcium reabsorption. By contrast, in parathyroid hormone-independent hypercalcemia, usually steadily progressive (the main cause being hypercalcemia of cancer), the primary event is almost always a rapid increase in the net calcium input in extracellular fluid. The attendant hypercalcemia is commonly poorly tolerated and induces a renal sodium leak and a decrease in extracellular fluid volume. The latter leads to a fall in glomerular filtration rate and a rise in tubular calcium reabsorption which, in turn, worsen hypercalcemia. Treatment includes a reexpansion of extracellular fluid volume and the inhibition of bone calcium release.

Calcium↗
PubMed1997

Pregnancy in women with impaired renal function.

The outcome and consequences of pregnancy in women with impaired renal function are still debated. To assess the benefit of recent advances in coordinated obstetrical and nephrologic management, we analyzed fetal and maternal outcome of 43 pregnancies in 30 women with various types of primary renal disease and moderate to severe renal failure at conception defined by serum creatinine concentration (Scr) ranging from 0.11 to 0.49 mmol/l. All pregnancies took place during the 20-year period from 1975 through 1994 and were prospectively followed jointly by our Nephrology Unit and Obstetric and Neonatology Units of University Hospitals. Of the 43 pregnancies (45 fetuses), 13 ended in fetal death (including 5 first-trimester abortions and 8 fetal deaths beyond the 20th gestational week). There were 32 live births, a success rate of 82% not considering first-trimester abortions. Successful pregnancies were significantly more frequent in the last decade than in the preceding one (91 vs 65%, p = 0.05). Overall live birth rate was higher in pregnancies started with Scr < 0.20 mmol/l than in those with Scr > 0.20 mmol/l (80% vs 53%, p = 0.02). The upper preconception Scr value associated with a successful fetal outcome was 0.27 mmol/l. Hypertension was the major factor of fetal prognosis, as the relative risk of fetal loss was 10.6 times higher when hypertension was present at conception or early in pregnancy than when blood pressure was spontaneously normal or well-controlled by therapy. An accelerated course toward end-stage renal failure was observed in 7 patients (23%), all of whom had severe hypertension and heavy proteinuria at conception. We conclude that fetal outcome in patients with impaired renal function has been improved in recent years, due to advances in obstetrics and neonatology, improved blood pressure control and close co-operation between nephrologists and obstetricians, but that a risk of fetal loss and of accelerated deterioration of maternal renal disease still persists when Ccr at conception is lower than 25-30 ml/ min/1.73 m2.

Adult↗
PubMed1996

Pregnancy in women with reflux nephropathy.

Reflux nephropathy is one of the most prevalent renal diseases and a leading cause of chronic renal failure in women-of childbearing age. To evaluate the issue and possible complications of pregnancy in women with reflux nephropathy, we retrospectively analyzed fetal and maternal outcome in 158 women who had 375 pregnancies between 1965 and 1994. The overall fetal death rate was 10.2% and tended to decrease in the 1985 to 1994 decade as compared to the preceding period (8.4% vs. 12.6%). The relative risk of fetal death was 4.8 times greater hypertension was present at conception than in normotensive patients. Fetal death rate was also higher in patients with impaired renal function that in those with serum creatinine < 0.11 mmol/liter at conception (36.7% vs. 7.7%, P < 0.0001). Urinary tract infection accounted for frequent morbidity but seldom resulted in fetal mortality. Maternal renal disease was unaffected by pregnancy, excepted for 4 of the 21 patients with pre-existing renal failure who exhibited an irreversibly accelerated course after pregnancy. We conclude that pregnancy is essentially successful and uneventful in patients diagnosed with reflux nephropathy who have normal blood pressure and preserved renal function, whereas the fetal prognosis is more compromised and there is a risk of accelerated progression of maternal renal disease when serum creatinine concentration is in excess of 0.22 mmol/ liter. This suggests that women with reflux nephropathy should preferably conceive before having reached that stage of renal failure.

Adolescent↗
PubMed1996

Calciuric response to an acute acid load in healthy subjects and hypercalciuric calcium stone formers.

Excessive animal protein consumption is associated with a greater risk of occurrence of renal calcium stone, presumably because of the attendant endogenous acid production. Indeed, chronic acid load enhances urinary calcium excretion possibly through an increased bone calcium release. Because acute studies are best designed to elucidate the mechanism, renal or extra renal, underlying hypercalciuria in the setting of enhanced acid load, we examined the response of 9 healthy adults (8 males, 1 female, aged 38 +/- 3 years, weight 67 +/- 2 kg) and 34 hypercalciuric recurrent calcium stone formers (31 males, 3 females, aged 44 +/- 2 years, weight 72 +/- 2 kg), without any associated disease, to an oral acid load (NH4Cl 2 mmol/kg body wt). After an overnight fast, each patient and control was studied during one one-hour period before and three two-hour periods after their intake of the acid load. An additional group of four time-control subjects (4 males, aged 33 +/- 2 years, weight 66 +/- 2 kg) was studied as the experimental groups except that they did not receive the acid load. On baseline, the three groups exhibited similar glomerular filtration rates, net acid excretions, and plasma calcium and magnesium concentrations. However, fasting urine calcium and magnesium excretions were higher in hypercalciuric calcium stone formers than in healthy control or time-control subjects. In time-control subjects, plasma acid base status, net acid excretion, filtered loads of calcium and magnesium, and urinary calcium and magnesium excretions remained unchanged all over the study. By contrast, after the oral acute acid load, net acid excretion increased and urinary pH decreased similarly in patient and control groups; glomerular filtration rate did not change, as well as plasma calcium and magnesium concentrations. Nevertheless, urinary calcium and magnesium excretions markedly increased, in both groups, independently of changes in tubular sodium handling and in plasma parathyroid hormone concentration. The increase in urinary calcium and magnesium excretions that occurred in the absence of any change in the filtered load of calcium and magnesium was therefore mediated by a decrease in tubular calcium and magnesium reabsorption, independent of PTH, but dependent on changes in net acid excretion. A positive linear relationship between urinary calcium and magnesium excretions suggested that the target tubular site for acid load was the thick ascending limb of Henle's loop. Finally, a negative linear relationship was demonstrated between the acid load-induced increase in urinary calcium excretion and fasting urinary calcium excretion; indeed, the lowest calciuric responses were observed in patients with the highest fasting urinary calcium excretion. Thus there was no additional effect of the acid load-induced inhibition on intrinsic defect in tubular calcium reabsorption which suggests that the tubular target site for acid load and the site of calcium transport defect in idiopathic hypercalciuria may be the same.

Acidosis↗
PubMed1996

Signaling pathways in the biphasic effect of angiotensin II on apical Na/H antiport activity in proximal tubule.

Low concentrations of angiotensin II (Ang II) increase, whereas high concentrations inhibit the apical Na/H antiporter activity in the proximal tubule, but the respective roles of the different signaling pathways in mediating these effects remains unsettled. We studied the effects of both low and high doses of Ang II in the presence of selective signaling pathway inhibitors, on the apical Na/H antiport activity of rat proximal tubule. Experiments were carried out in intact cells of freshly prepared tubule fragments obtained from the outer third of cortex, that is, devoid of basolateral Na/H antiport activity in the absence of bicarbonate transport and H(+)-ATPase activity. In tubules acid-loaded by an NH4Cl prepulse, Na/H antiport activity was assessed by the initial rate of intracellular pH recovery (dpHi/dt), measured with BCECF. When tubules were preincubated with low dose Ang II (10(-11) M for 3 min), dpHi/dt increased by 25 +/- 8%, whereas incubation with high dose Ang II (10(-7) M for 3 min) decreased dpHi/dt by 30 +/- 4%, compared to control (P < 0.01 in both cases). Both effects were abolished in the presence of 2.10(-3) M amiloride. Low dose Ang II-induced increase in dpHi/dt was not affected by preincubation with a specific PKA inhibitor, Rp-CPT-cAMP 10(-4) M, and was completely abolished by preincubation with PKC inhibitors, staurosporine 10(-7) M, sphingosine 5.10(-6) M, or calphostin 10(-6) M. In addition, pretreatment of rats with pertussis toxin led to a partial inhibition of the effect of low dose Ang II. The high dose-Ang II-induced decrease in dpHi/dt was not affected by pretreatment with a calcium-calmodulin kinase inhibitor W-7 10(-4) M. Conversely, pretreatment with the cytochrome P-450 inhibitor econazole 10(-5) M reversed the inhibitory effect of high dose Ang II to a stimulatory effect (24 +/- 8%, P < 0.01), quantitatively similar to the effect of low dose Ang II. In addition, arachidonate was found to exert an econazole-sensitive dose-dependent inhibitory effect on dpHi/dt, and 5,6-EET 10(-6) M, a cytochrome P-450 derived-arachidonic acid metabolite, induced a 38 +/- 9% inhibition, similar to that observed with high dose Ang II alone. There was no additive effect of 5,6-EET and high dose Ang II. Finally, pretreatment with two PLA2 inhibitors (BromoPhenacylBromide, 6.10(-6) M, and oleyloxyethyl phosphorylcholine, 5.10(-6) M) reversed the inhibitory effect of high dose Ang II to a stimulatory effect (32 +/- 11% and 25 +/- 11%, respectively, P < 0.05 for both inhibitors). We conclude that, in intact rat proximal cells, low dose Ang II stimulates the apical Na/H antiport through a pertussis toxin-sensitive G protein-dependent PKC pathway, whereas high dose Ang II inhibits the Na/H antiport activity through the PLA2- and cytochrome P-450-dependent metabolites of arachidonate.

Ammonia↗
PubMed1996

Oral calcium tolerance test in the early diagnosis of primary hyperparathyroidism and multiple endocrine neoplasia type 1 in patients with the Zollinger-Ellison syndrome. Groupe de Recherche et d'Etude du Syndrome de Zollinger-Ellison.

BACKGROUND: In patients with the Zollinger-Ellison syndrome, the exclusion of multiple endocrine neoplasia type 1 is of important clinical relevance. Its diagnosis often relies on the existence of primary hyperparathyroidism. AIM AND METHODS: To investigate the parathyroid function of patients with the Zollinger-Ellison syndrome by use of an oral calcium tolerance test to identify both hypercalcaemic and normocalcaemic primary hyperparathyroidism, and, accordingly, multiple endocrine neoplasia type 1. PATIENTS: Among 51 consecutive patients with the Zollinger-Ellison syndrome referred to us between 1988 and 1994, 28 had not been investigated for parathyroid function and were prospectively studied. RESULTS: The investigation of calcium metabolism was abnormal in nine patients. One displayed characteristic features of humoral hypercalcaemia of malignancy. The diagnosis of primary hyperparathyroidism was biologically established in eight patients (29%) and subsequently confirmed by the presence of hyperplasia of the parathyroid glands in the seven patients who underwent neck exploration. Three patients with primary hyperparathyroidism had fasting hyper-calcaemia but the other five had normal fasting serum total calcium concentration and the diagnosis of primary hyperparathyroidism was established by means of the oral calcium tolerance test. Primary hyperparathyroidism was demonstrated in the five patients in whom the diagnosis of multiple endocrine neoplasia type 1 had been previously established on other criteria than primary hyperparathyroidism. By contrast, in three patients, primary hyperparathyroidism, either hypercalcaemic (one patient) or normocalcaemic (two patients) was the sole criteria for the diagnosis of multiple endocrine neoplasia type 1. These results also suggest that primary hyperparathyroidism is present before or close to the time of Zollinger-Ellison syndrome diagnosis. CONCLUSION: Complete investigation of the parathyroid function with calcium calcium and parathyroid hormone concentrations.

Administration, Oral↗
PubMed1996

Calcitonin stimulates H+ secretion in rat kidney intercalated cells.

Calcitonin (CT) modulates rat intercalated cell (IC) functions of the rat cortical collecting duct (CCD) [E. Siga, B. Mandon, N. Roinel, and C. de Rouffignac. Am.J. Physiol. 264 (Renal Fluid Electrolyte Physiol. 33): F221-F227, 1993]. To characterize the specific function regulated by CT, rat CCDs were perfused in vitro. Total CO2 net fluxes (JtCO2, pmol.mm-1.min-1) and transepithelial voltage (Vt) were measured. Bath CT induced a significant tCO2 reabsorption. This effect was higher on CCDs harvested from acid-loaded than from control rats. When HCO3- secretion was blocked, CT also raised JtCO2 and Vt. When H+ secretion was blocked, CT was ineffective on JtCO2 and Vt. When HCO3- secretion was increased and H+ secretion was inhibited, CT did not change JtCO2, whereas isoproterenol (ISO) increased tCO2 secretion from -13.5 +/- 2.0 (control) to -19.0 +/- 2.4 (ISO). In rat CCD studied under these same preceding conditions plus luminal amiloride to block the Na(+)-dependent Vt, CT did not alter Vt, whereas ISO increased it by 4.5 +/- 0.7 mV. We conclude from these data that, in the rat CCD, calcitonin stimulates H+ secretion, likely by so-called alpha-intercalated (alpha-IC) cells, whereas ISO stimulates HCO3- secretion, likely by so-called beta-IC cells.

Acid-Base Equilibrium↗
PubMed1995

Influence of pregnancy on the course of primary chronic glomerulonephritis.

According to some nephrologists, pregnancy has damaging effects on renal function in primary glomerulonephritis, but the evidence is conflicting. We evaluated the effect of pregnancy on the occurrence of end-stage renal failure (ESRF) in 360 patients with various histological forms of primary glomerulonephritis but with normal renal function (serum creatinine < or = 0.11 mmol/L) at presentation. In actuarial analyses, overall ESRF-free survival did not significantly differ between women who became pregnant after clinical onset of renal disease (n = 171) and those who did not conceive (n = 189). Furthermore, in a case-control study pregnancy did not emerge as a risk factor for progression to ESRF (odds ratio 1.15 [95% CI 0.61-2.18]), whereas the type of glomerulonephritis and hypertension were major determinants. We conclude that pregnancy does not affect the course of renal disease in patients who have normal renal function at conception.

Adult↗
PubMed1993

[Exaggerated calciuric response to an acute acid load in patients forming renal calcium stones].

Calciuric response to an acute acid load was studied in 13 recurrent calcium stone formers and in 9 control subjects. The evolution of calcium and citrate urinary excretion related to creatinine, of plasma acid base status, of urinary pH, of acid excretion was analysed before and after NH4Cl administration (2 mmol/Kg). Fasting calciuria (expressed as Ca/Cr) was identical in the 2 groups, however the urinary calcium excretion after the acid load was greater in the stone formers group than in the controls (0.378 +/- 0.113 vs 0.253 +/- 0.108 mg/mg). The increase in acid excretion and the decrease in urinary citrate excretion were identical in the 2 groups.

Adult↗
PubMed1993

[Classification of renal tubular acidosis. Recent data].

In normal adults eating diets with standard protein contents, urinary excretion of NH4 approximates 40 mmol/24 hours and urinary pH is variable. In patients with metabolic acidosis, a urinary pH under 5.5 suggests an extra-renal cause whereas a urinary pH above 5.5 suggests a renal disorder, although there are many exceptions to this rule of thumb. However, urinary excretion of NH4 is always above 70 mmol/24 hours in extra-renal acidosis and less than or equal to 40 mmol/24 hours in renal acidosis; the two situations can readily be differentiated by determining the urinary anion gap which is absent in the former case and present in the latter. Acidosis due to nephron loss is readily diagnosed on the basis of advanced renal failure with an elevation in nonassayed plasma anions, contrasting with the increased serum chloride level found in tubular acidosis. Oral NaHCO3 loading followed by determination of the fractional excretion of HCO3 or, preferably, of the TmHCO3 normalized for glomerular filtration rate differentiates proximal tubular acidosis (decreased TmHCO3) from distal tubular acidosis (normal or increased TmHCO3). In the latter case, decreased serum potassium levels suggest distal tubular acidosis due to defective H(+)-ATPase or H+/K(+)-ATPase pump function (no increase in urinary PCO2 after oral NaHCO3 loading) or to inability of the kidney to develop a normal H+ gradient (normal increase in urinary PCO2). Increased serum potassium levels suggest conditions involving either hypoaldosteronism or alterations in transepithelial voltage or pseudo-hypoaldosteronism. The incidence of distal tubular acidosis with increased serum potassium levels is rising, whereas tubular acidosis with low serum potassium levels remains infrequent.

Acid-Base Equilibrium↗
PubMed1992

Chronic neutral phosphate supplementation induces sustained, renal metabolic alkalosis.

The aim of the present study was to test whether intravenous neutral phosphate supplementation, recently shown in our laboratory to acutely stimulate proton secretion in the distal nephron, was able to induce a sustained metabolic alkalosis. Neutral Na and K phosphate supplementation for seven days, with equivalent reduction in chloride supply and unchanged intake of sodium and potassium, in ADX rats receiving fixed physiological doses of aldosterone and dexamethasone (group 1, N = 7), was responsible for a severe metabolic alkalosis (MA; delta [HCO3] 11 +/- 1.3 mM, and delta pH 0.11 +/- 0.06 unit). Metabolic alkalosis was at least in part of renal origin, since net acid excretion (NAE) transiently increased, principally due to an increment in titratable acid excretion rate. Balances were equilibrated for sodium and negative for chloride and potassium, which may have contributed to the severity of the MA. Chronic i.v. neutral Na phosphate, without change in potassium and chloride supply, in ADX rats receiving the same doses of steroids (group 2, N = 5), was responsible for a less severe MA (delta [HCO3] 7.5 +/- 0.9 mM, and delta pH 0.07 +/- 0.01 unit), also of renal origin. In this group, balances were positive for chloride and sodium and equilibrated for potassium. Finally, neutral Na and K phosphate supplementation with reduction in chloride supply in intact rats (group 3, N = 4) was also able to induce a MA (delta [HCO3] 5.5 +/- 1.8 mM, and delta pH 0.06 +/- 0.01 unit) of renal origin, with balances negative for chloride and equilibrated for potassium and sodium. In all groups, the generation and maintenance of MA probably resulted from stimulated proton secretion in the distal nephron, as suggested by the observed increase of PCO2 over HCO3 concentration ratio in the urine and a fall in urine pH despite augmented urinary buffer content throughout the phosphate infusion period. Glomerular filtration rate did not significantly vary in any group. In conclusion, chronic supplementation of neutral phosphate appears to stimulate per se proton secretion in the distal nephron, independently of sodium, chloride, and potassium balances, and adrenal steroid secretion. Thus neutral phosphate supplementation should be added to the previously known factors able to induce MA.

Acid-Base Equilibrium↗