Phosphate In Rats Research Articles

Effect of an NHE3 inhibitor in combination with an NPT2b inhibitor on gastrointestinal phosphate absorption in Rodent models.

Many of the pathological consequences of chronic kidney disease can be attributed to an elevation in serum phosphate levels. Current therapies focused on decreasing intestinal phosphate absorption to treat hyperphosphatemia are inadequate. The most effective therapeutic strategy may be to target multiple absorptive pathways. In this study, the ability of a novel inhibitor of the intestinal sodium hydrogen exchanger 3 (NHE3), LY3304000, which inhibits paracellular, diffusional uptake of phosphate, to work in combination with an inhibitor of the active transporter, sodium dependent phosphate cotransporter 2b (NPT2b), LY3358966, was explored. LY3304000 modestly inhibited the acute uptake of phosphate into plasma of rats, while surprisingly, it doubled the rate of phosphate uptake in mice, an animal model dominated by NPT2b mediated acute phosphate uptake. In rats, LY3004000 and LY3358966 work in concert to inhibit acute phosphate uptake. On top of LY3358966, LY3304000 further decreased the acute uptake of phosphate into plasma. Studies measuring the recovery of radiolabeled phosphate in the intestine demonstrated LY3304000 and LY3358966 synergistically inhibited the absorption of phosphate in rats. We hypothesize the synergism is because the NHE3 inhibitor, LY3304000, has two opposing effects on intestinal phosphate absorption in rats, first it decreases diffusion mediated paracellular phosphate absorption, while second, it simultaneously increases phosphate absorption through the NPT2b pathway. NHE3 inhibition decreases proton export from enterocytes and raises the cell surface pH. In vitro, NPT2b mediated phosphate transport is increased at higher pHs. The increased NPT2b mediated transport induced by NHE3 inhibition is masked in rats which have relatively low levels of NPT2b mediated phosphate transport, by the more robust inhibition of diffusion mediated phosphate absorption. Thus, the inhibition of NPT2b mediated phosphate transport in rats in the presence of NHE3 inhibition has an effect that exceeds its effect in the absence of NHE3 inhibition, leading to the observed synergism on phosphate absorption between NPT2b and NHE3 inhibition.

Evaluation of immunohistochemical expression of collagen type I in bone defect treated by local application of collagen and beta-tricalcium phosphate in rats.

Aims: This study aimed to estimate outcome of combined application of collagen/β-tricalcium phosphate (Coll /β- TCP) on bone defect healing by immuno-histochemical localization of collagen type I. Materials and Methods: A total of 20 adult male rats (albino rats) were used in this study. Four intra bony defects were created in both femurs of each rat, three defects were treated with Coll, β- TCP and combination of Coll /β- TCP while forth defect left to heal spontaneously as control. Scarif i cation of animals was done after 2- and 4-weeks healing periods (10 rats for each). Immunohistochemical localization of collagen type I (COL1) monoclonal antibody was done for all bone specimens. Results: Immunohistochemical results showed positive expression of (COL1) by bone cells osteoblast (OB), osteocyte (OC), osteoclast (OCL) and bone marrow stromal cells (BMSCs) at 2- and 4-week duration for all examined groups with variable rates of intensity. Mean values of immunoreactive score (IRS) decreased with time for bone cells and for BMSCs except for OC where values increased with time as the highest values were recorded in combination group at 4 weeks. Conclusions: Combined application of (Coll /β- TCP) was ef f ective in accelerating bone healing process through elevating the IRS of (COL1) noticed by osteo-blast, osteocyte and bone marrow stromal cells.

Hepatic phosphate uptake and subsequent nerve-mediated phosphaturia are crucial for phosphate homeostasis following portal vein passage of phosphate in rats

Fibroblast growth factor 23, parathyroid hormone, and 1,25-dihydroxyvitamin D are critical in phosphate homeostasis. Despite these factors’ importance, regulators of phosphaturia in the acute postprandial phase remain largely unknown. This study investigated the mechanism of acute phosphate regulation in the postprandial phase in rats. Duodenal administration of radiolabeled phosphate (32P) showed that 32P levels in the inferior vena cava (IVC) blood were lower than those in the portal vein (PV) blood. Serum phosphate concentration transiently increased 5 min after phosphate solution administration through IVC, while it was maintained after the administration through PV. Phosphate administration through both IVC and PV resulted in increased fractional excretion of phosphate (FEPi) at 10 min without elevation of the known circulating factors, but urinary phosphate excretion during the period was 8% of the dose. Experiments using 32P or partial hepatectomy showed that the liver was one of the phosphate reservoirs. The elevation of FEPi and suppression of sodium-phosphate cotransporter 2a in the kidney at 10 min was attenuated in rats with SCH23390, hepatic denervation, or renal denervation, thus indicating that the liver communicated with the kidney via the nervous system to promote phosphaturia. These results revealed previously unknown mechanisms for serum phosphate maintenance.

Pretreatment with tadalafil attenuates cardiotoxicity induced by combretastatin A4 disodium phosphate in rats.

Combretastatin A4 disodium phosphate (CA4DP) is a prodrug of combretastatin A4 (CA4), a microtubule-disassembling agent that exhibits antitumor effects by inhibiting tumor cell proliferation and inducing morphological changes and apoptosis in vascular endothelial cells in tumors. However, cardiotoxicity induced by ischemia and hypertension is a severe adverse event. In this study, we focused on the fact that phosphodiesterase (PDE) 5 inhibitors dilate the heart and peripheral blood vessels and aimed to investigate whether co-administration of tadalafil, a PDE5 inhibitor, can attenuate cardiotoxicity without altering the antitumor effect of CA4DP. To investigate cardiotoxicity, CA4DP and/or tadalafil were administered to rats, and blood pressure, echocardiography, histopathology, and cGMP concentration in the myocardium were examined. Administration of CA4DP increased systolic blood pressure, decreased cardiac function, lowered cGMP levels in the myocardium, and led to necrosis of myocardial cells. Co-administration of tadalafil attenuated these CA4DP-induced changes. To investigate the antitumor effect, canine mammary carcinoma cell lines (CHMp-13a) and human umbilical vein endothelial cells were cultured with CA4 and/or tadalafil, and cell proliferation and endothelial vascular tube disruption were examined. CHMp-13a cells were transplanted into nude mice and treated with CA4DP and/or tadalafil. CA4-induced inhibition of cell proliferation and disruption of the endothelial vascular tube were not affected by co-treatment with tadalafil, and the antitumor effects of CA4DP in xenograft mice were not reduced by co-administration of tadalafil. These results revealed that myocardial damage induced by CA4DP was attenuated by co-administration of tadalafil while maintaining antitumor efficacy.

The Antioxidant Supplementation with Filipendula ulmaria Extract Attenuates the Systemic Adverse Effects of Nanosized Calcium Phosphates in Rats.

The aim of this study was to investigate and compare the systemic toxicity of three nanosized calcium phosphates (CaPs): hydroxyapatite (HA), tricalcium phosphate (TCP), and amorphous calcium phosphate (ACP) in rats. Since those metallic compounds are widely used as bone replacement materials, including their use in oral surgery, CaPs were applied (per os) equimollary (17.8 mg/kg, 11 mg/kg, and 9.65 mg/kg b.w., respectively) for 30 days in order to mimic the previously described release rate from dental composites. Also, we employed antioxidant supplementation with Filipendula ulmaria (FU) extract. All the applied CaPs significantly increased serum calcium, triglycerides, LDL, and LDH, while serum levels of testosterone and LH declined, with no alterations in the liver enzymes. The evaluation of oxidative stress markers (in the liver, kidney, and testicle) showed an increase in TBARS values, while SOD and CAT activities and GSH levels were significantly reduced. The relative gene expression of Bax and Bcl-2 was shifted to proapoptotic action, accompanied by intense characteristic histological changes in architecture in all investigated organs. The toxic effects were most prominent in groups treated by ACP. FU administration attenuated the majority of nanosized CaP-induced adverse effects, thus recommending this therapeutic approach to minimize nano-CaP systemic toxicities.

Histomorphometric evaluation of critical defects filled by β‐ tricalcium phosphate in rats calvary

Histomorphometric evaluation of critical defects filled by β‐ tricalcium phosphate in rats calvary

Ferric Pyrophosphate in Extruded, Fortified Rice Leads to Better Iron Outcomes Than Ferric Phosphate in Rats (P24-014-19)

ObjectivesRice fortification is a promising approach to reduce micronutrient deficiencies. Ferric phosphate (FePO4) and ferric pyrophosphate (FePP) have been suggested iron forms for their suitable organoleptic properties. Micronized FePP or the addition of citric acid (CA) and trisodium citrate (TSC) to FePP have been suggested to increase FePP bioavailability. Our primary objective was to compare iron bioavailability of extruded rice with these four iron fortificants. MethodsRice flour was fortified with a USDA MR24 vitamin/mineral blend and one of four iron fortificants: FePO4, FePP, micronized FePP, or FePP with CA and TSC (FePP + CA + TSC, ratio 1:0.1:2.1). Each extruded rice was blended at a 1:100 ratio with unenriched white rice. Soy protein isolate and soybean oil were added to the diets to meet growing rat nutritional requirements (15 g protein and 5 g fat/100 g diet) and cooked to approximately 40% added moisture content. Daily food intake and weekly body weights were measured in five groups (AIN-93 G or rice) of weanling, male Sprague Dawley rats (n = 10). Each group consumed assigned diet for 21-days, when the study was terminated because of poor growth in the rice groups. Blood and livers were collected to evaluate iron outcomes and bone mineral density (BMD) and body composition were assessed with PIXImus scans. ResultsAll rice groups had significantly lower moisture-adjusted total food intake, weight gain, final weight, and BMD compared to the AIN-93 G group with no differences in these outcomes between the rice groups. There were no differences in either iron outcome between the different FePP fortificants. Hemoglobin levels were significantly higher in the FePP and micronized FePP groups compared to the FePO4 and AIN-93 G groups. Hepatic iron levels were significantly higher in the FePP, micronized FePP, and FePP + CA + TSC groups compared to the FePO4 and AIN-93 G groups. ConclusionsWhile they need to be interpreted with some caution because of poor growth, our results suggest that FePP leads to better iron outcomes than FePO4. However, neither micronizing nor adding CA + TSC to FePP improved iron outcomes. Funding SourcesPartially funded by the USDA Foreign Agricultural Service under the Micronutrient Fortified Food Aid Products Pilot (MFFAPP) program and the Kansas Agricultural Experiment Station.

Intestinal Response to Acute Intragastric and Intravenous Administration of Phosphate in Rats.

Phosphate (Pi) homeostasis is controlled by the intestine and kidneys whose capacities to transport Pi are under endocrine control. Several studies point to intestinal absorption as a therapeutic target to modulate Pi homeostasis. The small intestine is responsible for almost all Pi absorption in the gut, a process involving Na+-dependent and independent mechanisms. Three Na+-dependent Pi cotransporters have been described in the gastrointestinal tract: NaPi-IIb (a SLC34 member) and Pit-1 and Pit-2 (SLC20 transporters). We recently analysed the acute hormonal and renal response to intragastric (i.g) and intravenous (i.v) Pi-loading. This study demonstrated that the kidney quickly adapts to Pi-loading, with changes manifesting earlier in the i.v than i.g intervention. The aim of this work was to extend the previous studies in order to investigate the acute adaptation of intestinal transport of Pi and expression of intestinal Na+/Pi-cotransporters in response to acute Pi-loading. Duodenal and jejunal mucosa was collected 40 minutes and/or 4 hours after administration (i.g and i.v) of either NaCl or Pi to anaesthetized rats. Uptakes of Pi and protein expression of Na+/Pi cotransporters were measured in brush border membrane vesicles (BBMV); the cotransporters' mRNA abundance was quantified by real-time PCR in total RNA extracted from whole mucosa. Pi-loading did not modify transport of Pi in duodenal and jejunal BBMV 4 hours after treatment. Administration of Pi did not alter either the intestinal expression of NaPi-IIb and Pit-2 mRNAs, whereas Pit-1 mRNA expression was only regulated (diminished) in duodenum collected 4 hours after i.g Pi-loading. NaPi-IIb protein expression was decreased in duodenum 4 hours upon i.v Pi infusion, whereas the duodenal and jejunal abundance of the cotransporter was unaffected by i.g administration of Pi. Together, these data suggest that the intestine responds acutely to Pi-loading, though this response seems slower than the renal adaptation.

Impaired Phosphate Tolerance Revealed With an Acute Oral Challenge.

Elevated serum phosphate is consistently linked with cardiovascular disease (CVD) events and mortality in the setting of normal and impaired kidney function. However, serum phosphate does not often exceed the upper limit of normal until glomerular filtration rate (GFR) falls below 30 mL/min/m2 . It was hypothesized that the response to an oral, bioavailable phosphate load will unmask impaired phosphate tolerance, a maladaptation not revealed by baseline serum phosphate concentrations. In this study, rats with varying kidney function as well as normo-phosphatemic human subjects, with inulin-measured GFR (13.2 to 128.3mL/min), received an oral phosphate load. Hormonal and urinary responses were evaluated over 2 hours. Results revealed that the more rapid elevation of serum phosphate was associated with subjects and rats with higher levels of kidney function, greater responsiveness to acute changes in parathyroid hormone (PTH), and significantly more urinary phosphate at 2 hours. In humans, increases in urinary phosphate to creatinine ratio did not correlate with baseline serum phosphate concentrations but did correlate strongly to early increase of serum phosphate. The blunted rise in serum phosphate in rats with CKD was not the result of altered absorption. This result suggests acute tissue deposition may be altered in the setting of kidney function impairment. Early recognition of impaired phosphate tolerance could translate to important interventions, such as dietary phosphate restriction or phosphate binders, being initiated at much higher levels of kidney function than is current practice. © 2017 American Society for Bone and Mineral Research.

Osteoconductive action of alendronate after implantation of beta tricalcium phosphate in rat adjuvant-induced arthritis

The aim of the study was to determine the effect of alendronate on resorption of β-tricalcium phosphate (β-TCP) and bone formation in rats with adjuvant-induced arthritis (AIA). After preparation of a model of AIA in rats (day 0), alendronate or vehicle was injected intraperitoneally once daily five times in a week. Cylindrical β-TCP was implanted into the rat femoral condyle on day 7. Rats were killed on days 12, 15, and 21, and specimens and serum samples were collected. Specimens were analyzed by tartrate-resistant acid phosphate (TRAP) staining, immunohistochemistry of the ED1 protein, and in situ hybridization with digoxigenin-labeled α1 chain of type I procollagen (COL1A1). Mineralized bone sections were analyzed by Villanueva bone stain. The serum osteocalcin level was measured using an enzyme-linked immunosorbent assay kit. Alendronate decreased the number of TRAP-positive cells attached to β-TCP, the numbers of ED1-positive multinucleated giant cells, and resorption of β-TCP. In AIA rats treated with alendronate, COL1A1 mRNA-positive cells adhered to β-TCP were round or cuboid whereas the cells in untreated AIA rats were fibroblast-like cells. Alendronate increased calcification of newly formed bone whereas it did not restore the bone formation suppressed with inflammation. These results suggest that alendronate has the potential to conduct mature bone after implantation of β-TCP in AIA. Alendronate may help to reduce insufficiency of newly formed bone after implantation of β-TCP in diseases characterized by increased bone resorption such as rheumatoid arthritis.

Pharmacological inhibition of the hypertensive response to combretastatin A-4 phosphate in rats

Combretastatin A-4 phosphate (CA4P) is a novel and promising anti-neoplastic agent. However, it is associated with transient hypertension in both animal and human models. In this study, we examined the potential cardiac toxicity and hypertensive effects of CA4P, and defined the most effective pharmacological inhibition of CA4P-induced hypertension in rats. There was a significant, concentration dependent increase in mean arterial blood pressure with a maximum increase of about 60% of the baseline MAP at 30 mg/kg of CA4P compared to the saline control. However, there was no significant increase in the cardiac troponin I level after CA4P injection. Nitroglycerin and the calcium channel blocker diltiazem effectively blocked the hypertensive effects of CA4P while the beta blocker metoprolol was ineffective. Furthermore, sublingual nitroglycerin administration demonstrated an additional anti-hypertensive effect in a setting of a low dose diltiazem infusion (10 µg/kg/min). We conclude that CA4P treatment resulted in a concentration dependent increase in blood pressure without significant myocardial damage in healthy rats. The hypertensive effect of CA4P was effectively blocked by both nitroglycerin and diltiazem, but not metoprolol.

Effect of chitosan structure properties and molecular weight on the intranasal absorption of tetramethylpyrazine phosphate in rats

The objective of this work was to assess and compare the absorption promoting effect of different molecular-weight chitosans, trimethyl chitosans and thiolated chitosans for intranasal absorption of 2,3,5,6-tetramethylpyrazine phosphate (TMPP). An in situ nasal perfusion technique in rats was utilized to test the rate and extent of TMPP absorption in situ. In vivo studies were carried out in rats and the pharmacokinetic parameters were calculated and compared with that of intravenous injection. All the chitosan derivatives investigated could enhance the intranasal absorption of TMPP significantly. However, thiolation could not improve the absorption-enhancing capacity of chitosan remarkably even when the thiolation ratio was as high as 152 μmol/g. In contrast, trimethylated chitosan exhibited stronger absorption-enhancing ability than the homopolymer chitosan. The permeation enhancing effect of chitosan increased with increasing molecular weight up to M w 100 kDa. In vivo studies indicated that chitosan 100 kDa and TMC 50 kDa had comparable absorption-enhancing effect but chitosan 100 kDa functioned for more than 120 min versus 90 min for TMC. A good correlation was found between the in situ absorption data and plasma concentration in vivo for the polymers investigated. This study demonstrated that both chitosan structural features and chitosan molecular weight play a key role on promoting the intranasal absorption of TMPP. Taking safety reason into account, chitosan 100 kDa is the most promising as an intranasal absorption enhancer.

Old age and gender influence the pharmacokinetics of inhaled manganese sulfate and manganese phosphate in rats

In this study, we examined whether gender or age influences the pharmacokinetics of manganese sulfate (MnSO4) or manganese phosphate (as the mineral form hureaulite). Young male and female rats and aged male rats (16 months old) were exposed 6 h day−1 for 5 days week−1 to air, MnSO4 (at 0.01, 0.1, or 0.5 mg Mn m−3), or hureaulite (0.1 mg Mn m−3). Tissue manganese concentrations were determined in all groups at the end of the 90-day exposure and 45 days later. Tissue manganese concentrations were also determined in young male rats following 32 exposure days and 91 days after the 90-day exposure. Intravenous 54Mn tracer studies were also performed in all groups immediately after the 90-day inhalation to assess whole-body manganese clearance rates. Gender and age did not affect manganese delivery to the striatum, a known target site for neurotoxicity in humans, but did influence manganese concentrations in other tissues. End-of-exposure olfactory bulb, lung, and blood manganese concentrations were higher in young male rats than in female or aged male rats and may reflect a portal-of-entry effect. Old male rats had higher testis but lower pancreas manganese concentrations when compared with young males. Young male and female rats exposed to MnSO4 at 0.5 mg Mn m−3 had increased 54Mn clearance rates when compared with air-exposed controls, while senescent males did not develop higher 54Mn clearance rates. Data from this study should prove useful in developing dosimetry models for manganese that consider age or gender as potential sensitivity factors.

Old age and gender influence the pharmacokinetics of inhaled manganese sulfate and manganese phosphate in rats

In this study, we examined whether gender or age influences the pharmacokinetics of manganese sulfate (MnSO 4) or manganese phosphate (as the mineral form hureaulite). Young male and female rats and aged male rats (16 months old) were exposed 6 h day −1 for 5 days week −1 to air, MnSO 4 (at 0.01, 0.1, or 0.5 mg Mn m −3), or hureaulite (0.1 mg Mn m −3). Tissue manganese concentrations were determined in all groups at the end of the 90-day exposure and 45 days later. Tissue manganese concentrations were also determined in young male rats following 32 exposure days and 91 days after the 90-day exposure. Intravenous 54Mn tracer studies were also performed in all groups immediately after the 90-day inhalation to assess whole-body manganese clearance rates. Gender and age did not affect manganese delivery to the striatum, a known target site for neurotoxicity in humans, but did influence manganese concentrations in other tissues. End-of-exposure olfactory bulb, lung, and blood manganese concentrations were higher in young male rats than in female or aged male rats and may reflect a portal-of-entry effect. Old male rats had higher testis but lower pancreas manganese concentrations when compared with young males. Young male and female rats exposed to MnSO 4 at 0.5 mg Mn m −3 had increased 54Mn clearance rates when compared with air-exposed controls, while senescent males did not develop higher 54Mn clearance rates. Data from this study should prove useful in developing dosimetry models for manganese that consider age or gender as potential sensitivity factors.

Oral Phosphate Binders: Phosphate Binding Capacity of Iron (III) Hydroxide Complexes Containing Saccharides; and Their Effect on the Urinary Excretion of Calcium and Phosphate in Rats

Phosphate binders that contain aluminum or calcium are frequently prescribed to treat hyperphosphatemia in patients with end-stage renal disease (ESRD), but an accumulation of aluminum can lead to encephalopathy, aluminum related bone disease (ARBD) such as osteomalacia, anaemia, and resistance to erythropoietin, and calcium accumulation can lead to hyperculcaemia. High phosphate concentrations are reducd in vitro and in vivo by a phosphate adsorption pill, which is synthesized by hydrolyzing ferrous sulfate in the presence of saccharides, to form an iron (III)-saccharide complex that is acid resistant anti binds phosphate greater than iron (III) hydroxide alone. Under in vitro conditions, containing 3.26 mg P/dL, the iron (III)-sucrose complex showed the highest phosphate adsorption capacity at pH 2 with artificial gastric juice, 58.9 mg P/g binder. For the 7 day in vivo study, 0% (Group 1), 1% (Group 2), 4% (Group 3), and 8% (Group 4) iron (III)-sucrose complex was admixed into the rodent chow by weight and fed to 15 male Wistar rats. The weight and volume of the feces and urine, and the calcium, iron, and phosphorus excretions in the feces and urine samples were monitored for any signs of irregularity. Total urine outfrow was collected during a 24-h period to determine the amount of phosphate recovered, which indicates the ability of the phosphate binder to reduce gastrointestinal phosphate absorption. The fecal iron excretion was significantly effected by the amount of binder ingested throughout the study for Group 2 (p < 0.001), Group 3 (p < 0.01), and Group 4 (p < 0.001). The urinary calcium excretion (mg/rat/24-h) significantly increased by the 7th day for Group 2 (p < 0.05) and Group 4 (p < 0.01) in comparison to the control. Finally, after 7 days, there was a significant drop in the urinary phosphorus levels (mg P/rat/24-h) in a dose dependant manner for Group 2: from 7.82 ± 1.46 to 1.98 ± 0.10 mg P/rat/24-h (102 mg P/dL/24-h; p < 0.05); Group 3: from 6.70 ± 1.14 to 0.16 ± 0.09 mg P/rat/24-h (6.0 mg P/dL/24-h; p < 0.01); and Group 4: fiom 8.25 ± 0.67 to 0.04 ± 0.01 mg P/rat/24-h (0.9 mg P/dL/24-h; p < 0.01). The results show that this new adsorbent might provide an alternative to conventional aluminum and calcium containing phosphate-binding agents for combating hyperphosphataemia.

Effect of acute hypoxia on phosphate excretion in rats

This study evaluated the effect of acute hypoxia on renal handling of phosphate in rats in the presence and absence of parathyroid hormone (PTH). Hypoxia causes respiratory alkalosis in spontaneously breathing humans and animals. Respiratory alkalosis has been reported to induce a blunted phosphaturic response to PTH. In this study, to avoid the confounding effect of hypocapnia accompanying the hypoxia on phosphate excretion, the rats were ventilated mechanically, and arterial PCO2 levels were controlled. Rats were divided into two main groups depending on the arterial PO2 levels: a hypoxic group (n = 16) and a normoxic group (n = 18). Hypoxia was produced by ventilating with 10% oxygen, and hypocapnia was produced by hyperventilation. In response to PTH, the hypoxic rats without hypocapnia showed a greater increase in fractional excretion of phosphate (FEPi; 37.7 +/- 2.6%, mean +/- SE) compared with normoxic rats (27.4 +/- 2.5%, P < 0.02). During hypocapnia, there was no difference in FEPi between hypoxic and normoxic groups (21.2 +/- 1.5 and 19.5 +/- 1.2%, respectively), and both groups showed a significantly blunted phosphaturic response to PTH compared with normocapnia (P < 0.05 and P < 0.01, respectively). Urinary adenosine 3',5'-cyclic monophosphate (cAMP) increased similarly after PTH infusion between each group. To test whether the phosphaturic effect of PTH in hypoxia and the blunted phosphaturic effect of PTH in hypocapnia are due to steps beyond the generation of cAMP, the phosphaturic response to cAMP infusion was evaluated in 1) hypoxic and normocapnic rats (n = 6), 2) normoxic and normocapnic (control) rats (n = 6), and 3) normoxic and hypocapnic rats (n = 7).(ABSTRACT TRUNCATED AT 250 WORDS)

Cytotoxicity of Fecal Water Is Dependent on the Type of Dietary Fat and Is Reduced by Supplemental Calcium Phosphate in Rats

The effects of the type of dietary fat (180 g/kg diet) and of calcium phosphate (CaHPO4) supplementation (25 vs. 225 mmol/kg diet) on luminal solubility of fatty acids and bile acids, cytotoxicity of fecal water and intestinal epitheliolysis were studied in rats. In rats fed the low and high calcium phosphate diets, fecal excretion of fatty acids diminished in the order palm oil > milk fat > corn oil. Palm oil also caused the highest concentration of fatty acids measured in fecal water followed by milk fat and corn oil when fed at both calcium phosphate levels. The differences in concentrations of luminal surfactants in fecal water of rats fed the three fat diets resulted in a fat type-dependent cytotoxicity of fecal water, with that of palm oil-fed rats the most cytotoxic. The concentrations of fatty acids as well as bile acids in fecal water were, however, significantly lowered by calcium phosphate supplementation in rats fed all types of dietary fat. This reduction in concentration of fecal water surfactants resulted in a lower cytotoxicity of fecal water. The concentration of surfactants in fecal water and cytotoxicity were correlated by multiple regression analysis (R = 0.89). Intestinal epitheliolysis measured as alkaline phosphatase activity in fecal water was lowered comparably to the reduction in cytotoxicity by supplemental calcium phosphate. Intestinal epitheliolysis and cytotoxicity of fecal water were correlated (r = 0.92, P < 0.001). The type of dietary fat and the amount of dietary calcium phosphate influence the concentrations of surfactants in fecal water and consequently affect cytotoxicity of fecal water and intestinal epitheliolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Feeding regimen and diurnal rhythms of serum calcium and phosphate in rats

Diurnal rhythms of serum Ca, Pi, Mg and alkaline phosphatase activity (Al-Pase) were investigated in rats with particular reference to their feeding schedules. The following results were obtained: 1) Serum Ca, Pi, Mg and Al-Pase in ad libitum fed rats who had experienced a 12/12h dark-light cycle (with light from 6∶00 to 18∶00) for more than 2wk showed significant diurnal rhythms. Basically the same diurnal patterns were observed even in fasting conditions. 2) A scheduled food restriction (food was available from 8∶00 to 16∶00) for more than 10 days resulted in shifts or modifications in the previously obtained diurnal curves. Of these modified rhythms, the Ca and Mg rhythms followed essentially the same patterns as those seen with the restricted feeding schedule for at least 24h even with subsequent fasting, but the Pi and Al-Pase rhythms did not. The above results suggest that the rhythms seen in the described restricted feeding may come under two categories: One is a rhythm which appears to couple with an endogeneous mechanism associated with the cyclic feeding stimuli and can persist at least for a certain period of time even in the fasting condition. The other is a rhythm which is modified only transiently by the feeding stimuli and may couple with another endogeneous oscillating mechanism associated with the synchronizer(s) other than the cyclic feeding stimuli.

Isolation and identification of metabolites of 2-ethylhexyl diphenyl phosphate in rats.

The metabolic fate of 2-ethylhexyl diphenyl phosphate (EHDPP) was studied in male rats. Orally administered 14C-EHDPP was rapidly absorbed and about 80% of the radioactivity was excreted in the urine and feces in the first 24 h. By 7 days, 48% and 52% of the radioactivity was recovered in urine and feces, respectively. Since biliary excretion was low (6% for 2 days), urine seems to be the major excretion route of EHDPP. Radioactivity was widely distributed in all tissues examined. At 2 h, the concentration was relatively high in blood, liver kidney and adipose tissue. The elimination of radioactivity from adipose tissue and liver was somewhat delayed, but almost all the radioactivity was eliminated by 7 days. The major metabolites in the urine were diphenyl phosphate (DPP) and phenol. p-Hydroxyphenyl phenyl phosphate (OH-DPP) and monophenyl phosphate (MPP) were also identified as minor metabolites.

Comparative studies on absorption, distribution, and excretion of flame retardants halogenated alkyl phosphate in rats.

Comparative studies on the absorption, distribution, and excretion of flame retardants, tris (2, 3-dibromopropyl) phosphate (TDBPP), bis (2, 3-dibromopropyl) phosphate (BDBPP), tris (1, 3-dichloro-2-propyl) phosphate (TDCPP), tris (1-chloro-2-propyl) phosphate (TMCPP) and tris (2-chlorethyl) phosphate (TMCEP), were carried out in rats. During 168 h after an oral administration of an equimolar dose (50 μmol/kg) of these 14C-labeled flame retardants, the decreasing order of levels of 14C-radioactivity excreted was TMCEP»TMCPP>TDBPP>BDBPP>TDCPP in urine, TDCPP>TDBPP>BDBPP>TMCPP»TMCEP in feces, and BDBPP>TDCPP>TDBPP»TMCPP>TMCEP in expired air. The amounts remaining in the carcass were in the order TDBPP=BDBPP>TDCPP>TMCEP=TMCPP. Almost 100% of the radioactivity administered was recovered, in the ranges of 43.2 to 93.4% in urine, 5.6 to 39.2% in feces, 1.7 to 19.4% in expired air (as 14CO2), and 0.7 to 3.7% in the body. Biliary excretion of the five flame retardants ranged from 24.6 to 44.9% of the dose by 48 h. The order of biliary excretion was as follows : TMCPP>TDCPP>BDBPP=TDBPP>TMCEP. Tris- or bis- (dihalogenated alkyl) phosphates were more slowly absorbed, distributed and excreted than tris (monohalogenated alkyl) phosphates. In binding studies in vitro, the order of covalent binding to S-9 of liver and kidney was as follows : TDBPP>MDBPP>BDBPP.