B. Lacour

Influence of tumor necrosis factor-α on the expression and function of P-glycoprotein in an immortalised rat brain capillary endothelial cell line, GPNT

Drug cerebral pharmacokinetics may be altered in the case of inflammatory diseases. This may be due to a modification of drug transport through the blood-brain barrier, in particular through drug interaction with the membrane efflux transporter, P-glycoprotein. The objective of this study was to investigate the influence of the inflammatory cytokine, tumor necrosis factor (TNF)-alpha, on the functionality and expression of P-glycoprotein, and on mdr1a and mdr1b mRNA expression in immortalised rat brain endothelial cells, GPNT. Cells were treated with TNF-alpha for 4 days. Levels of mdr1a and mdr1b mRNAs were quantitated using real-time RT-PCR analysis and expression of P-glycoprotein was analyzed by Western blot. The functionality of P-glycoprotein was studied by following the accumulation of [3H]vinblastine in the cells without and with a pre-treatment with a P-glycoprotein inhibitor, GF120918. TNF-alpha increased the levels of mdr1a and mdr1b mRNAs while no effect was observed on protein expression. TNF-alpha increased [3H]vinblastine accumulation indicating a time and concentration-dependent decrease of P-glycoprotein activity. This effect was eliminated when the cells were pre-treated with GF120918. Our observation of a decrease in P-glycoprotein activity could suggest that in the case of inflammatory diseases, brain delivery of P-glycoprotein-dependent drugs can be enhanced.

Serum Lipoprotein Disturbances in Primary and Secondary Hyperparathyroidism and Effects of Parathyroidectomy

Serum lipoprotein disturbances were studied in 86 patients with primary (I), and 34 hemodialysis patients with severe secondary (II), hyperparathyroidism (HPTH) before and seven to 14 days after parathyroidectomy (PTx). In addition, a subset of patients had repeat studies more than 12 months after PTx. In patients with I as well as with II HPTH, mean +/- SEM fasting serum concentrations of total triglycerides (TG) (1.51 +/- 0.09 and 2.17 +/- 0.19 mmol/L, respectively) were significantly increased when compared with that of 22 age- and sex-matched healthy control subjects (1.01 +/- 0.09 mmol/L, P less than .001). No consistent anomalies of serum total cholesterol and lipoprotein cholesterol content were observed in Io HPTH patients. In uremic II HPTH patients, the cholesterol content of high-density lipoprotein (HDL) was significantly (P less than .01) depressed, compared with normal subjects. In the short term, PTx normalized serum total TGs (P less than .001) in Io HPTH patients from 1.50 +/- 0.11 to 1.19 +/- 0.07 mmol/L seven days after PTx. The surgical correction of II HPTH in dialysis patients was also followed by an improvement of hypertriglyceridemia from 2.22 +/- 0.21 to 1.46 +/- 0.08 mmol/L and 1.46 +/- 0.09 mmol/L seven and 14 days, respectively, after PTx (P less than .01). Long-term follow-up after PTx shows clearly a persistent decrease in serum TG concentration in I HPTH patients (1.17 +/- 0.11 mmol/L), as well as in II HPTH patients (1.61 +/- 0.18 mmol/L), 12 months after PTx by comparison with values determined before PTx.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption and efficiency of insulin after oral administration of insulin-loaded nanocapsules in diabetic rats.

Poly(isobutylcyanoacrylate) nanocapsules have been shown to decrease the blood glucose level after oral administration to streptozotocin-induced diabetic fasted rats after 2 days [Diabetes 37 (1988) 246]. Yet, the absorption of insulin in the blood of rats has not been characterised. The aim of this work was to evaluate the biological activity of insulin given orally as nanocapsules. Humalog-loaded nanocapsules (50 IU/kg) were administered by gavage to streptozotocin-induced diabetic rats. Thirty minutes to 1 h after oral administration, significant levels of human insulin were detected in rat plasma. However, the concentrations were very heterogenous from one rat to another and no decrease of glycemia could be observed. In addition, parenteral injection of insulin in solution showed that high levels of the protein are necessary to decrease blood glucose concentration in diabetic rats. These concentrations were not reached after oral administration. The same dose of insulin decreased glycemia by 50% in normal rats and by only 25% in diabetics. This suggested that an insulino-resistance was developed by streptozotocin-induced diabetic rats.

Comparison of Several Atherogenicity Indices by the Analysis of Serum Lipoprotein Composition in Patients with Chronic Renal Failure with or without Haemodialysis, and in Renal Transplant Patients

We investigated serum lipoproteins in uraemic and kidney transplant patients, and compared the results with those from normal persons. In uraemic patients, with or without haemodialysis, and in kidney transplant patients, the ratio of HDL-cholesterol to total cholesterol minus HDL-cholesterol, the ratio of HDL-phospholipids to total phospholipids minus HDL-phospholipids, and the ratio of apolipoprotein A to apolipoprotein B are all decreased, though to different extents, when compared with healthy control subjects. Furthermore, important differences exist in the relative HDL composition between the 3 patient groups and healthy control subjects. Thus, the ratio of apolipoprotein A/HDL-cholesterol and that of HDL-cholesterol/HDL-phospholipids are significantly altered in uraemic haemodialyzed patients, while the ratio of apolipoprotein A/HDL-phospholipids is normal. By contrast, the 3 ratios are normal in uraemic undialyzed patients, and the 2 ratios, apolipoprotein A/HDL-cholesterol and apolipoprotein A/HDL-phospholipids are normal in renal transplant patients. The last ratio, HDL-cholesterol/HDL-phospholipids, is increased in this group of patients. Thus, it appears that HDL-cholesterol, HDL-phospholipids, and total apolipoprotein A represent different aspects of the same lipoprotein. The determination of all three parameters could lead to a different approach in the evaluation of the so-called cardiovascular risk, at least for uraemic patients and renal transplant patients.

Role of transcellular pathway in ileal Ca2+ absorption: stimulation by low-Ca2+ diet

The present study was performed to determine the respective involvement of the cellular and paracellular routes in ileal Ca2+ transport. Two groups of rats were either fed a normal Ca2+ diet (1.0%) or a Ca2+-deficient diet (0.02%) for 14 days. Ileal Ca2+absorption was determined using both an in situ method of continuous luminal perfusion and an in vitro method (Ussing chamber model). The low-Ca2+ diet stimulated net Ca2+ flux in the ileum twofold, associated with a twofold increase of the mucosal-to-serosal Ca2+ flux in both models. This effect was observed in the absence of concomitant changes in Na+ or water flux in the in situ model or mannitol flux in the in vitro model, excluding the participation of the paracellular pathway in Ca2+ transport. Thus only cellular Ca2+ flux was stimulated. These data suggest that the ileum plays a major role in the adaptation to low dietary Ca2+. Whereas under physiological conditions with usual Ca2+ intakes the transcellular pathway of Ca2+ transport is negligible, it becomes of major importance in the case of Ca2+ deficiency, at least under the present conditions of severe Ca2+ deprivation.

Paraquat detoxication with multiple emulsions

In this study, we show that detoxifying W/O/W multiple emulsions, prepared with an appropriate extractant/trapping couple, represent a promising technology for quick and safe poisoning treatments, with application to the highly toxic herbicide Paraquat, responsible of poisonings from low-dose exposure leading to several deaths every year. In vitro tests led to the choice of an appropriate extractant/trapping couple system with significant detoxication performance. In vivo tests showed (i) that rats receiving high doses of Paraquat, then a detoxifying emulsion, presented an increase from 50% to 100% of the MST (median survival time) and (ii) that no mortality was observed during 30 days with rats dosed with emulsions initially loaded with Paraquat at a concentration much higher than the lethal dose, proving the stability and the inocuity of the detoxifying multiple emulsion in the gastrointestinal tract.

Effect of Acute Ethanol Loading on Parathyroid Gland Secretion in the Rat

Acute ethanol loading in the rat induces hypocalcemia and hypermagnesemia. In addition, hypocalcemia is not corrected by exogenous PTH. In the rat the mechanism of these changes was investigated by measuring plasma immunoreactive parathyroid hormone (PTH). PTH was also measured in culture medium in which parathyroid glands were incubated. The addition of ethanol to test tubes did not interfere with PTH measurement. Absolute ethyl alcohol diluted to 50% with distilled water was administered via an intragastric tube. It failed to induce an increase in plasma immunoreactive PTH level. Similarly, it prevented an increase in plasma PTH after disodium EDTA injection. Thus in the presence of ethyl alcohol plasma PTH failed to increase in spite of a significant decrease of plasma calcium. In vitro studies showed that the decrease of calcium concentration of the medium from 1.50 to 0.75 mmol/l was associated with a 3 to 5 times increase in PTH secretion rate. This increase was suppressed when ethanol was added to the culture medium. In conclusion, ethanol loading via gastric tubing induced: 1) decrease in plasma calcium; 2) suppression of immunoreactive PTH secretion in the presence of hypocalcemia. It is postulated that the acute hypocalcemic effect of ethanol loading is mediated by a dual effect at the level of the bone and the parathyroid gland.

Effect of dietary docosahexaenoic acid on the endothelium‐dependent vasorelaxation in diabetic rats

1. The aim of the present study was to investigate the responses to acetylcholine (ACh; 3 nmol/L−30 µmol/L) and sodium nitroprusside (SNP; 3 nmol/L−30 µmol/L) of precontracted aortic rings from diabetic rats supplemented with docosahexaenoic acid (DHA).

Plasma and Pituitary Content of Growth Hormone Luteinizing Hormone, and Prolactin in Uremic Rats

The influence of chronic renal failure on pituitary content and on serum concentrations of growth hormone (GH), prolactin (PRL), and luteinizing hormone (LH) was studied in chronically uremic rats by comparison with control rats fed ad libitum and diet-restricted rats pair-fed with uremic rats. A decrease of pituitary GH content was found in uremic and diet-restricted rats, in association with a normal circulating GH level. A decrease of pituitary PRL and LH content with respectively high and normal serum values was observed in uremic but not in diet-restricted rats. These data strongly suggest that GH disturbances are related to malnutrition, whereas PRL and LH abnormalities are related to the uremic state per se. As hypoinsulinemia was observed in uremic rats, and as insulin is largely implicated in growth, we have investigated the effects of chronic infusion of insulin, using miniosmotic pumps, on pituitary hormone content. In spite of normalization of circulating insulin levels in uremic rats treated with insulin, pituitary GH, LH, and PRL contents were unaffected. Thus, insulin deficiency did not appear to be responsible for the diminished pituitary reserve of these hormones.

Effects of hyperoncotic albumin and parathyroid hormone infusion on jejunal electrolyte and water absorption in the rat.

Preferential plasma volume expansion by infusion of hyperoncotic albumin solution dialyzed against distilled water (calcium-poor albumin) decreases sodium reabsorption in the dog proximal renal tubule during hydropenia. No such decrease is observed when infusing a calcium-rich hyperoncotic albumin solution. A possible role of parathyroid hormone (PTH) has been postulated. To investigate whether similar changes could be observed in intestinal electrolyte and water absorption, the effects of systemic hyperoncotic albumin infusion on jejunal transport of water, sodium, and calcium were studied in hydropenic rats by perfusing proximal jejunum in situ. It was further sought whether PTH could play a direct role in jejunal electrolyte and water transfer.Following infusion of calcium-poor, sodium-poor hyperoncotic albumin solution (group I), net jejunal absorption of water, sodium, and calcium decreased significantly when compared to control. Concurrently, lumen-to-mucosa (1-m) calcium flux, measured using 45 Ca, diminished significantly. Following infusion of calcium-rich, sodium-poor hyperoncotic albumin solution (group II), no changes in net or unidirectional fluxes were observed. After infusion of calcium-rich, sodium-rich hyperoncotic albumin solution (group III), net jejunal absorption of water and sodium, but not of calcium, were found significantly decreased when compared to control.Plasma ionized calcium increased 10 min after calcium-rich hyperoncotic albumin loading, but decreased significantly at that time when the calcium-poor hyperoncotic albumin solution was infused. However, 30 min after each of the calcium-rich and calcium-poor albumin infusion, plasma ionized calcium was increased in both groups of rats. Plasma immunoreactive PTH was unchanged 30 min after expansion with the calcium-rich solution but it increased significantly after expansion with the calcium-poor solution.Intravenous infusion of bovine PTH (group IV) resulted in a decrease of net jejunal water, sodium, and calcium flux. The decrease in net calcium transport was accompanied by a decrease in 1-m calcium flux. No such changes were observed when PTH was replaced by vehicle (group V).It is concluded that: (1) hyperoncotic albumin infusion induces jejunal water, sodium, and calcium flux changes dependent on the calcium and sodium content of the infused solution: calcium-poor, sodium-poor hyperoncotic albumin infusion leads to a decrease in net jejunal electrolyte and water absorption possibly via stimulation of PTH secretion; (2) sodium-poor hyperoncotic albumin infusion does not modify per se these fluxes in the hydropenic rat; (3) exogenous PTH infusion as well as endogenous stimulation of PTH secretion results in a comparable decrease of jejunal water, sodium, and calcium absorption.