Injection Of EDTA Research Articles

Effect of Mineral Element Imbalance on Neutrophil Respiratory Burst Function and Inflammatory and Antioxidant Responses in Sheep

This study established a model of mineral element homeostatic imbalance and examined the respiratory burst function of peripheral blood neutrophils and inflammatory and antioxidant indicators before and after the imbalance in sheep. The results showed that after an EDTA injection, the number of activated neutrophils in the peripheral blood was significantly higher than that in the control group (p < 0.01). In addition, the serum IL-6 level was significantly increased (p < 0.05) and matrix metalloproteinase 7 (MMP7) was inhibited (p < 0.05), but returned to a normal level one week after the injection. Tissue inhibitor of metalloproteinase 1 (TIMP1) levels were consistently higher after the injection and significantly higher than in the control group (p < 0.05). CuZn-SOD, TNOS activity, serum creatinine and urea nitrogen levels were significantly higher than before the injection (p < 0.05). Combining the results of previous studies, the EDTA injection altered the metabolism and transcription of peripheral blood neutrophils. These changes enhance the respiratory burst function of neutrophils and alter the status of inflammatory and antioxidant indicators such as IL-6 and CuZn-SOD.

Transcriptomic Analysis of Circulating Neutrophils in Sheep with Mineral Element Imbalance.

This experiment was designed to investigate the effects of mineral element imbalance on gene transcription in peripheral circulating neutrophils of sheep. Ten female sheep weighing 30kg of similar age and physiological condition were randomly selected and injected via central venous catheterization with EDTA at a concentration of 4% (W/V) to construct a model of mineral element imbalance. As self-control, the sheep were divided into control [Con, before EDTA injection, time point 0 (T0)], EDTA [12h after EDTA injection, time point 12h (T12h)] and recovery [HF, 7days after injection, time point 7days (T7d)] groups. Whole blood was collected, and serum and neutrophils were separated for ionomic and transcriptomic analysis. The results showed that levels of P (P < 0.05), Zn (P < 0.01), K (P < 0.01) and some other elements were significantly lower in sheep in the EDTA group than in those in the control group, but levels of P (P > 0.05), Zn (P > 0.05) and K (P > 0.05) were similar in the recovery and control groups. Levels of Ca (P > 0.05) and Cu (P < 0.05) were higher after injection, and levels of Cu (P < 0.01) continued to increase during the recovery period. There were 1561 genes, including S100 family genes, significantly differentially expressed in neutrophils between the control and trial groups, and these genes were mainly enriched in the categories defense response, immune response, regulation of interleukin production and other functions. The top enriched signaling pathways were phagosome, NF-κB and Toll-like receptor. Mineral element homeostasis imbalance affected the gene transcriptome of circulating neutrophils, demonstrating the importance of carefully controlling the addition of mineral elements.

New Insights into EDTA In Vitro Effects on Endothelial Cells and on In Vivo Labeled EDTA Biodistribution

EDTA chelation therapy has recently been proposed for the treatment of patients affected by neurodegenerative (ND) or cardiovascular (CVD) diseases due to its efficacy in removing toxic metals that affect the functions of neurons and endothelial cells. We examined the effects of EDTA in modulating human umbilical vein endothelial cell (HUVEC) activation induced by tumor necrosis factor alpha (TNFα). Moreover, we studied the biodistribution of technetium [99 mTc] EDTA injected intravenously into healthy adult rats. Our results show that EDTA treatment reverses the HUVEC activation induced by TNFα, as highlighted by normal tubulin distribution, in keeping with a well spread, quiescent endothelial phenotype. In addition, the biodistribution of labeled EDTA reaches the central nervous system (CNS), as assessed by scintigraphy (5853.6 cpm/pixel measured at 1 hour following intravenous labeled EDTA injection) and autopsy data (3.67% at 3 hours following labeled EDTA intravenous injection). Such evidence highlights new insights into the usefulness of EDTA chelation therapy in the treatment of ND and CVD.

Sesame and resistant starch reduce the colon carcinogenesis and oxidative stress in 1,2-dimethylhydrazine-induced cancer in Wistar rats

Whole sesame paste (WSP) and resistant starch type 2 (RS2) have been shown to have health benefits. This in vivo study evaluated the protective effect of 1,2-dimethylhydrazine (DMH) on colon carcinogenesis in rats on diets containing WSP and RS-2. Four formulations were produced according to AIN-93G, as follows: A (control); B (WSP); C (WSP and RS2); and D (RS2), using a twin-screw extruder in the same conditions. Weaned Wistar male rats were divided into 8 groups of 8 animals each. The animals were fed the diets over 28days and received injections of DMH or EDTA from days 14 to 21. There was no significant (Tukey's test, p<0.05) difference in growth profile, liver and muscle glycogen in rats on all diets. In the DMH groups, the protective effect of both WSP and RS2 was observed for diets B, C, and D, reducing from 60 to 80% the values of aberrant crypt foci (ACF) and aberrant crypt (AC), and from 98 to 100% the mucin-depleted ACF, and with reduction in oxidative stress as compared to the control diet (Kruskal–Wallis, p<0.05). These results indicate that both the antioxidant compounds in sesame and the products of colonic fermentation of resistant starch were beneficial to protect the mucosa against chemical carcinogenesis induced by DMH.

Pituitary tumorous hyperplasia due to primary hypothyroidism

BackgroundTo study the diagnostic and therapeutic features of pituitary tumorous hyperplasia due to primary hypothyroidism.MethodsFifteen patients with pituitary tumorous hyperplasia were studied in clinical manifestation, pathologic, endocrinological, radiographic and therapeutic features retrospectively.ResultsAll of these patients suffered from primary hypothyroidism. Magnetic resonance imaging (MRI) scanning found that there were masses in the sellar region with equal T1 and little longer T2 signal, and which could be obviously enhanced by gadolinium EDTA injection. Diameters of these masses were between 1.1 and 2.5 cm. Thyroxine substitution therapy was ordered. Four months later, MRI scanning found that the masses disappeared and only normal pituitary gland left. Plasma thyroxine, thyroid-stimulating hormone (TSH), and prolactin (PRL) levels dropped to their normal ranges.ConclusionsThyroxine substitution therapy was the first choice of pituitary tumorous hyperplasia due to primary hypothyroidism. If they are followed by TSH adenoma, or the optic chiasma was pressed by the enlarged pituitary, transsphenoidal microsurgery could be applied.

Behavioral response of chicks exposed to manganese by drinking water and mobilization of body manganese burden by EDTA

Manganese (Mn) is a neurotoxicant in various animal species including the chicks. The present study examines the effect of Mn on the behavioral response of chicks, plasma and tissue Mn levels and the effect of the metal chelating agent disodium EDTA in reducing high levels of the metal in the plasma and some vital organs. Day old chicks were provided with either deionized water (control group) or with Mn at 1 g/L of deionized water as the drinking water for 14 days. On treatment days 7 and 14, all chicks were individually monitored for 3-min open-field activity and then they were subjected to tonic immobility test. On days 7 and 14, the concentrations of Mn in the plasma, whole brain, liver and kidney were determined by atomic absorption spectrometry. Seven or eight day-old chicks were treated intramuscularly (i.m.) with either saline at 5 ml/kg (control), Mn at 20 mg/kg followed 30 min later with saline, or with Mn at 20 mg/kg followed 30 min later with EDTA at 50 mg/kg. The concentrations of Mn in the plasma, whole brain, liver and kidney were determined two hours after the Mn injection by atomic absorption spectrometry. Mn increased the general locomotor activity of the chicks in the open-field arena (lines crossed) and decreased the duration of tonic immobility response of the chicks on treatment day 14 in comparison with the control group. The administration of Mn in the drinking water at 1 g/L increased Mn concentrations in the plasma, whole brain, liver and kidney of the chicks on days 7 and 14 in comparison with the control values. Higher levels of Mn were attained on day 14 compared with those of day 7. Injection of Mn at 20 mg/kg significantly increased the metal concentrations in the plasma, whole brain, liver and kidney of the chicks. The highest concentration of Mn appeared in the kidney followed by the liver, whole brain and the plasma. Injection of EDTA at 50 mg/kg significantly reduced Mn concentrations in the plasma and whole brain when compared with those of the saline-treated group. The data suggest that Mn is well absorbed and distributed into the tissues after exposure of young chicks via the drinking water or i.m. Mn changed the behavioral performance of the chicks and EDTA effectively reduced acute Mn overload in the body. These results further support and expand previous studies concerning the experimental use of young chicks as a potential model of acute Mn neurotoxicity.

Heavy Metal Removal from Shooting Range Soil by Hybrid Electrokinetics with Bacteria and Enhancing Agents

This study presents a method for heavy metal removal from a shooting range soil by a newly suggested hybrid technology. Active bioaugmentation was performed using Acidithiobacillus thiooxidans in the bioleaching step, and each test was sequentially combined with acid-enhanced and EDTA-enhanced electrokinetics. The results of the bioleaching processes indicated that S-oxidizing bacteria enhanced the mobility of heavy metals in the soil, based on their chemical forms. This process improved the final removal efficiencies of Cu and Zn in the hybrid electrokinetics. In the case of Pb, however, anglesite (PbSO(4)) has been easily formed in the bioleaching step from sulfate, a byproduct of S oxidation. Despite the potential negative effect on combining acid-enhanced electrokinetics, this problem was overcome by the application of an electrokinetic EDTA injection. Moreover, this method showed enhanced removal efficiency for Pb (92.7%) that was superior to that of an abiotic process. This hybrid method of EDTA-enhanced bioelectrokinetics demonstrated an adequate removal efficiency of heavy metals, especially Pb, with lower power consumption and eco-friendly soil conditions.

Upregulation of parathyroid VDR expression by extracellular calcium is mediated by ERK1/2-MAPK signaling pathway

We have previously demonstrated that the activation of rat parathyroid calcium-sensing receptor (CaSR) upregulates VDR expression in vivo (Garfia B, Cañadillas S, Luque F, Siendones E, Quesada M, Almadén Y, Aguilera-Tejero E, Rodríguez M. J Am Soc Nephrol 13: 2945-2952, 2002; Rodriguez ME, Almaden Y, Cañadillas S, Canalejo A, Siendones E, Lopez I, Aguilera-Tejero E, Martin D, Rodriguez M. Am J Physiol Renal Physiol 292: F1390-F1395, 2007). The present study was designed to characterize the signaling system that mediates the stimulation of parathyroid VDR gene expression by extracellular calcium. Experiments were performed in vitro by the incubation of rat parathyroid glands and in vivo with normal and uremic (Nx) rats receiving injections of CaCl(2) or EDTA to obtain hypercalcemic or hypocalcemic clamps. A high calcium concentration increased VDR expression. The addition of arachidonic acid (AA) to the low-calcium medium produced an increase in VDR mRNA of the same magnitude as that observed with high calcium. The addition of ionophore to the low-calcium medium also increased VDR mRNA expression. High calcium or the addition of AA to the low-calcium medium induced the activation (phosphorylation) of ERK1/2-MAPK. The specific inhibition of the ERK1/2-MAPK activity prevented the stimulation of VDR expression by high calcium or AA. These results suggest that AA regulates parathyroid VDR gene expression through the activation of the ERK1/2-MAPK. CaSR activation induced the activation of transcription factor Sp1, but not of NF-κB p50 or p65 or activator protein-1. The addition of AA to the low-calcium medium increased specific DNA-binding activity of Sp1 to almost the same level as high calcium, which was prevented by the inhibition of ERK1/2. Furthermore, mithramycin A (a Sp1 inhibitor) prevented the upregulation of VDR mRNA by high calcium. Finally, both sham and Nx hypercalcemic rats showed similar increased levels of VDR mRNA compared with sham and Nx hypocalcemic rats. Our results demonstrate that extracellular calcium stimulates VDR expression in parathyroid glands through the elevation of the cytosolic calcium level and the stimulation of the PLA(2)-AA-dependent ERK1/2-pathway. Furthermore, the transcription factor Sp1 mediates this effect.

N-methyl-d-aspartate receptors are expressed in rat parathyroid gland and regulate PTH secretion

N-methyl-d-aspartate receptors (NMDAR) are tetrameric amino acid receptors which act as membrane calcium channels. The presence of the receptor has been detected in the principal organs responsible for calcium homeostasis (kidney and bone), pointing to a possible role in mineral metabolism. In the present work, the presence of the receptor was determined in normal parathyroid glands (PTG) by real-time PCR, immunoprecipitation, and immunohistrochemistry. Healthy animals showed a decrease in blood parathyroid hormone (PTH) levels 15 min after the treatment with NMDA. This effect was also observed in animals with high levels of PTH-induced EDTA injection, but not in uremic animals with secondary hyperparathyroidism (2HPT). Normal rat PTG incubated in media with low calcium concentration (0.8 mM CaCl2) showed a decrease in PTH release when NMDA was added to the media. This effect of NMDA was abolished when glands were coincubated with MK801 (a pharmacological blocker of the NMDA channel) or PD98059 (an inhibitor of the ERK-MAPK pathway). Glands obtained from animals with 2HPT showed no effect of NMDA in the in vitro release of PTH, together with a decrease in the expression of NMDAR1. In conclusion, NMDA receptor is present in PTG and is involved in the regulation of the PTH release. The mechanism by which NMDAR exerts its function is through the activation of the MAPK cascade. In uremic 2HPT animals the receptor expression is downregulated and the treatment with NMDA does not affect PTH secretion.

Human FXYD2 G41R mutation responsible for renal hypomagnesemia behaves as an inward-rectifying cation channel

A mutation in the human FXYD2 polypeptide (Na-K-ATPase gamma subunit) that changes a conserved transmembrane glycine to arginine is linked to dominant renal hypomagnesemia. Xenopus laevis oocytes injected with wild-type FXYD2 or the mutant G41R cRNAs expressed large nonselective ion currents. However, in contrast to the wild-type FXYD2 currents, inward rectifying cation currents were induced by hyperpolarization pulses in oocytes expressing the G41R mutant. Injection of EDTA into the oocyte removed inward rectification in the oocytes expressing the mutant, but did not alter the nonlinear current-voltage relationship of the wild-type FXYD2 pseudo-steady-state currents. Extracellular divalent ions, Ca2+ and Ba2+, and trivalent cations, La3+, blocked both the wild-type and mutant FXYD2 currents. Site-directed mutagenesis of G41 demonstrated that a positive charge at this site is required for the inward rectification. When the wild-type FXYD2 was expressed in Madin-Darby canine kidney cells, the cells in the presence of a large apical-to-basolateral Mg2+ gradient and at negative potentials had an increase in transepithelial current compared with cells expressing the G41R mutant or control transfected cells. Moreover, this current was inhibited by extracellular Ba2+ at the basolateral surface. These results suggest that FXYD2 can mediate basolateral extrusion of magnesium from cultured renal epithelial cells and provide new insights into the understanding of the possible physiological roles of FXYD2 wild-type and mutant proteins.

Regulation of parathyroid vitamin D receptor expression by extracellular calcium.

Low extracellular calcium (Ca) stimulates parathyroid hormone (PTH) secretion and also increases the renal synthesis of calcitriol (CTR), which is known to decrease PTH production. This study began with the hypothesis that the parathyroid cell response to CTR may be modulated by extracellular Ca concentration through an effect on parathyroid cell vitamin D receptor (VDR). In the present study, rat parathyroid glands were incubated in low (0.6 mM) and high (1.5 mM) Ca concentration. The parathyroid VDRmRNA was higher in 1.5 than 0.6 mM Ca. Furthermore, this effect was not observed in incubated slices of kidney cortex and medulla, tissues which also possess both Ca and vitamin D receptors. Experiments were also performed to evaluate the effect of Ca on VDR expression in vivo. Male Wistar rats received intraperitoneal injections of CaCl(2) or a single intramuscular injection of EDTA to obtain 6 h of hypercalcemic (ionized Ca, 1.4 to 1.6 mM) or hypocalcemic (ionized Ca, 0.85 to 0.95 mM) clamp; a third group of rats was used as control. A small dose of CTR was administered to hypercalcemic rats to match the serum CTR levels of hypocalcemic rats. Parathyroid gland VDRmRNA and VDR protein were increased in hypercalcemic rats as compared with hypocalcemic rats. Increasing doses of CTR upregulated VDRmRNA and VDR only in hypercalcemic rats. Additional experiments showed that the decrease in VDR in hypocalcemic rats prevented the inhibitory effect of CTR on PTHmRNA. In conclusion, our study shows that extracellular Ca regulates VDR expression by parathyroid cells independently of CTR and that by this mechanism hypocalcemia may prevent the feedback of CTR on the parathyroids.

Radionuclide studies in paediatric nephro-urology

The main tool of radionuclide techniques applied to paediatric uro-nephrology is the quantitation of function, which is an information not easily obtained by other diagnostic modalities. The radiation burden is low. Drug sedation is only rarely needed, whatever the age of the patient. Accurate determination of glomerular filtration rate can be obtained by means of an intravenous injection of Cr-51 EDTA and one or two blood samples. Tc-99m DMSA scintigraphy is an accurate method for evaluation of regional cortical impairment during acute pyelonephritis and later on, for detection of permanent scarring. Tc-99m MAG3 renography is nowadays a well-standardized method for accurate estimation of the split renal function and of renal drainage with or without furosemide challenge. This technique is particularly indicated in uni- or bilateral uropathies with or without renal and/or ureteral dilatation. Direct and indirect radionuclide cystography are two alternative modalities for X-ray MCUG. Their relative place in the strategy of management of vesicoureteral reflux is discussed.

Action potential bursts in central snail neurons elicited by d-amphetamine: roles of ionic currents

The roles of the ionic currents in the firing of potential bursts elicited by d-amphetamine in central snail neurons were studied in the identified RP4 neuron of the African snail, Achatina fulica Ferussac, using the two-electrode voltage-clamp method. Oscillations of membrane potential bursts were elicited by d-amphetamine. The action potential bursts elicited by d-amphetamine decreased following intracellular injection of either EDTA or magnesium, or extracellular application of lanthanum. Voltage-clamped studies revealed that d-amphetamine decreased the fast Na +, Ca 2+ and transient outward K + currents of the RP4 neuron. It also decreased the steady-state K + current and elicited a negative slope resistance in the steady-state I–V curve between −50 and −10 mV. The amplitude of negative slope resistance was decreased if either Na +-free saline or Co 2+-substituted Ca 2+-free saline was perfused. d-Amphetamine did not increase the amplitude of the slowly inactivating Ca 2+ current or the persistent Na + currents of RP4 neuron. Tetraethylammonium, a blocker of the delayed outward K + current, elicited action potential bursts and negative slope resistance in the RP4 neuron, while 4-aminopyridine, an inhibitor of transient outward K + current (I A), did not. These results demonstrate that the delayed outward K + current and the negative slope resistance in steady-state I–V curve elicited by d-amphetamine may be responsible for the action potential bursts in central snail neurons elicited by d-amphetamine.

The Effects of[formula omitted]-Arginine on Crypt Cell Hyperproliferation in Colorectal Cancer

Background.Colonic crypt cell hyperproliferation characterizes malignant and premalignant conditions of the colon and may be modified by dietary manipulation. This study compared the effect of dietary arginine supplementation on colonic crypt cell proliferation during the initiation and promotion stages of colorectal carcinogenesis.Materials and Methods.One hundred and twenty male Wistar rats were divided into 5 groups of 24 animals each. Groups D, DA, FA, and LA received subcutaneous injections of 1,2-dimethylhydrazine for 20 weeks. Group D received no arginine supplement.l-arginine was given as a 1% solution instead of drinking water to Group DA for 22 weeks, to Group FA for the first 10 weeks, and to Group LA for the last 12 weeks. EDTA animals were given subcutaneous injections of EDTA for 20 weeks. Colonic crypt cell proliferation was assessed in 6 animals from each of the five groups and in 6 normal rats not given DMH or EDTA.Results.The BrdUrd-labeling index and proliferative zone were significantly decreased in all arginine groups (DA, FA, LA). The greatest reduction was evident in Group FA in which tumor incidence and tumor size were also significantly lowered.Conclusions.When given during the initiation phase of carcinogenesisl-arginine significantly reduced colorectal tumor production and crypt cell hyperproliferation.

Influence of anesthetics on endogenous and recombinantly expressed G protein-coupled receptors in the Xenopus oocyte

1. The oocyte of the African clawed toad ( Xenopus laevis) offers a reliable, sensitive and disease resistant system to investigate recombinantly and endogenously expressed Ca 2+ signaling G protein-coupled receptors and their intracellular signaling pathways. 2. To study receptor induced Ca 2+ release, two-electrode voltage clamping can quantify a Ca 2+-activated transmembrane Cl − current. Intracellular steps of the signaling pathway can be inhibited by injections of EDTA or heparin into the oocyte. Components of the intracellular pathway can be activated directly by GTP γS or IP 3 injection. 3. We have investigated the effects of volatile, local and i.v. anesthetics on the signaling properties of the endogenous lysophosphatidate receptor and on mammalian receptors expressed recombinantly by intracellular injection of the encoding mRNA or cDNA. A number of receptors are sensitive to these anesthetics. Anesthetics interact with muscarinic, thromboxane A 2 and lysophosphatidate signaling. 4. Investigations of the intracellular pathways revealed that the receptor or the receptor-G protein coupling is affected primarily and that mechanisms further downstream are not influenced by the various types of anesthetics.

Acute copper intoxication after a Cu–Ca EDTA injection in rats

It has been claimed that Cu–Ca EDTA releases the Cu slowly into the blood when injected as a therapeutic agent for Cu deficiency, but when overdosing occurs, animals may die in a few hours after the injection, suggesting that Cu release is faster than expected. A total of 30 rats were divided into six equal groups and injected with Cu–Ca EDTA at 4, 6, 13, 33 or 64 mg/kg body weight, the sixth group acted as control. All rats were sacrificed 24 h later, with the exception of rats from groups 33 and 64 that died 7 and 2 h postinjection respectively. The rate of Cu transference to the liver increased linearly with the dose, from (X±S.E.) 14. 88±3.14 in group 4, to 134.47±21.86 μg/h in group 64. Injected animals developed liver and kidney degeneration, hemorrhage and necrosis, which increased in severity with the Cu dose. Liver Cu accumulation was highest for group 13 (866.8±84.23 ppm DM), while in group 64 reached only 167.0±14.99 ppm. It is concluded that during acute Cu poisoning, the rate of transfer is responsible for the liver and kidney damage, rather than the total amount of transferred Cu to those organs, as it is the case in chronic Cu poisoning. The high rate of Cu transfer possibly surpasses the intrinsic mechanisms of Cu deposition and free Cu is left into the cell with the development of necrosis.

Neuromodulation of activity-dependent synaptic enhancement at crayfish neuromuscular junction

Action potential-evoked transmitter release is enhanced for many seconds after moderate-frequency stimulation (e.g. 15 Hz for 30 s) at the excitor motorneuron synapse of the crayfish dactyl opener muscle. Beginning about 1.5 s after a train, activity-dependent synaptic enhancement (ADSE) is dominated by a process termed augmentation (G.D. Bittner, D.A. Baxter, Synaptic plasticity at crayfish neuromuscular junctions: facilitation and augmentation, Synapse 7 (1991) 235–243 [4]; K.L. Magleby, Short-term changes in synaptic efficacy, in: G.M. Edelman, L.E. Gall, C.W. Maxwell (Eds.), Synaptic Function, John Wiley and Sons, New York, 1987, pp. 21–56; K.L. Magleby; J.E. Zengel, Augmentation: a process that acts to increase transmitter release at the frog neuromuscular junction, J. Physiol. (Lond.) 257 (1976) 449–470) which decays approximately exponentially with a time constant of about 10 s at 16°C, reflecting the removal of Ca 2+ which accumulates during the train in presynaptic terminals (K.R. Delaney, D.W. Tank, R.S. Zucker, Serotonin-mediated enhancement of transmission at crayfish neuromuscular junction is independent of changes in calcium, J. Neurosci. 11 (1991) 2631–2643). Serotonin (5-HT, 1 μM) increases evoked and spontaneous transmitter release several-fold (D. Dixon, H.L. Atwood, Crayfish motor nerve terminal's response to serotonin examined by intracellular microelectrode, J. Neurobiol. 16 (1985) 409–424; J. Dudel, Modulation of quantal synaptic release by serotonin and forskolin in crayfish motor nerve terminals, in: Modulation of Synaptic Transmission and Plasticity in Nervous Systems, G. Hertting, H.-C. Spatz (Eds.), Springer-Verlag, Berlin, 1988; S. Glusman, E.A. Kravitz, The action of serotonin on excitatory nerve terminals in lobster nerve–muscle preparations, J. Physiol. (Lond.) 325 (1982) 223–241). We found that ADSE persists about 2–3 times longer after moderate-frequency presynaptic stimulation in the presence of 5-HT. This slowing of the decay of ADSE by 5-HT was not accompanied by significant changes in the initial amplitude of activity-dependent components of enhancement 1.5 s after the train. Measurements of presynaptic [Ca 2+] indicated that the time course of Ca 2+ removal from the presynaptic terminals after trains was not altered by 5-HT. Changes in presynaptic action potential shape, resting membrane potential or postsynaptic impedance after trains cannot account for slower recovery of ADSE. Axonal injection of EDTA slows the removal of residual Ca 2+ and the decay of synaptic augmentation after trains of action potentials (K.R. Delaney, D.W. Tank, A quantitative measure of the dependence of short-term synaptic enhancement on presynaptic residual calcium, J. Neurosci. 14 (1994) 5885–5902), but has little or no effect on the 5-HT-induced persistence of ADSE. This also suggests that the time course of ADSE in the presence of 5-HT is not determined primarily by residual Ca 2+ removal kinetics. The slowing of ADSE recovery after trains by 5-HT reverses with washing in 5-HT-free saline along with the 5-HT-mediated enhancement of release.

Assessment of renal function by 51Cr‐EDTA and endogenous creatinine clearances in the pig

In anaesthetized pigs, clearances of 51Cr-EDTA (EDTA) and endogenous creatinine were compared with renal clearance of inulin measured during constant infusion after bolus injection. Creatinine was determined by enzymatic (Kodak Ektachem) as well as conventional (Jaffé) methods. In saline-loaded pigs, renal clearance of constantly infused EDTA was 97.0 +/- 6.7 mL min-1 and identical to the clearance of inulin (94.1 +/- 9.1 mL min-1). There was good agreement between individual clearances. The extraction fractions of the two markers were indistinguishable (0.26 +/- 0.02 and 0.28 +/- 0.03, respectively). In other experiments the clearance of EDTA calculated from the first 4 h of the time course of the plasma concentration after single injection was 64.4 +/- 3.7 mL min-1, correlating well with inulin clearance (63.0 +/- 1.2 mL min-1). When calculated only from the monoexponential phase of the disappearance curve ('slope clearance'), significantly higher results were obtained (+33%, P < 0.001). Renal clearance of EDTA after single injection was 7.5 +/- 1.5 mL min-1 (approximately 12%) lower than inulin clearance (P < 0.001). Values of creatinine clearances determined by the two analytical methods showed a poor agreement with inulin clearance. It is concluded that, in pigs, glomerular filtration rate may be estimated by the clearance of EDTA using constant infusion or single injection of EDTA and that the renal clearance of endogenous creatinine is a less useful a measure of GFR.

The influence of cervical sympathetic neurons on parathyroid hormone and calcitonin release in the rat: independence of pineal mediation.

The objective of this study was to evaluate the involvement of the pineal gland in modulation of parathyroid hormone (PTH) and calcitonin release found in rats after changes in activity of cervical sympathetic nerves. The response of serum PTH to a hypocalcemia produced by EDTA injection, and of serum calcitonin to a hypercalcemia produced by administering calcium chloride, were studied in rats at the time of the wallerian degeneration of regional sympathetic nerves (i.e., 16 hr after superior cervical ganglionectomy, SCGx). Rats received a pinealectomy or its sham-operation 4 days before SCGx. During wallerian degeneration of nerves after SCGx, a higher hypocalcemia and a lower PTH response were found as compared to sham-SCGx rats, regardless of whether the pineal gland was present or not. When the response of calcitonin to a bolus injection of calcium chloride was assessed, rats subjected to SCGx 16 hr earlier showed a depressed calcitonin release, which was also unaffected after pinealectomy. To a similar extent in pinealectomized and sham-pinealectomized rats, a mild stress given by the subcutaneous injection of turpentine oil brought about a greater hypocalcemia after EDTA, concomitantly with a higher PTH secretory response. In turpentine oil-injected rats, the rise of serum calcitonin was significantly greater than that of vehicle-treated rats, regardless of pineal presence. The results further indicate that cervical autonomic nerves constitute a pathway through which the brain modulates calcium homeostasis and do not support the participation of the pineal gland in short term changes of PTH or calcitonin release.

Calcium Homeostasis—An Old Problem Revisited

This article proposes a novel model of calcium homeostasis, based on the concept of a series of bone calcium-binding sites of varying calcium affinities. When an i.v. Ca load is administered to mammals, it is rapidly (t1/2 < 1 min) dispersed into a volume equivalent to the extracellular fluid. Thereafter the calcium concentration drops monoexponentially with a t1/2 of tens of minutes. When a negative Ca load is administered, as by EDTA injection, the return to the preinjection plasma Ca level, [Cas], occurs also monoexponentially at the same rate as restoration after a positive load. The numerical value of the rate can be arrived at by taking into account the fraction of cardiac output (5%) that is directed to the skeleton. Acute regulation is brought about by controlling access to subpopulations of the Ca binding sites, whose average Km determines [Cas]. Osteoblasts, when active and extended, block low-affinity binding sites; osteoclasts, when active and extended, block high-affinity sites. Exposure of sites is brought about when bone cells respond by rapid shape changes, osteoblasts rounding up in response to parathyroid hormone (PTH) or vitamin D, osteoclasts rounding up in response to calcitonin. These shape changes are the first steps in the cascade of events that lead to bone formation and resorption, but acute regulation need not involve the latter steps of a cascade. The model accounts for the changes in the response times to Ca loads that have been observed in older animals or those deprived of PTH, calcitonin or vitamin D.