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PubMed1975

Effects of synthetic buffers on reflexes in the isolated frog spinal cord.

Substitution of synthetic buffers (Tris, TES, HEPES, or 3,3-dimethylglutarate) for CO2-bicarbonate buffer in Ringer solution perfusing the isolated in vitro frog spinal cord preparation altered membrane properties and reflex activity. Perfusion with Ringer solution gassed with O2 and containing synthetic bu,fers consistently produced a depolarization of motoneurons and dorsal root fibers, decreased the amplitude (and usually the duration) of ventral and dorsal root potentials, and had variable effects on motoneuron and dorsal root reflex discharges. With Tris-Ringer these discharges decreased in amplitude; with Ringer containing one of the other synthetic buffers, these discharges were augmented. All changes were reversible when the cord was returned to bicarbonate-buffered Ringer aerated with 95% O2/5% CO2. The use of a combined buffer system-one containing a synthetic buffer and bicarbonate-induced smaller or minimal changes in bioelectric activity. At present the data are insufficient to allow firm conclusions concerning the mechanisms underlying these results; but it is evident 1) that changes in PCO2 and bicarbonate concentration and 2) that the pharmacological properties of synthetic buffers are important variables.

Animals↗
PubMed1997

Symmetric pH dependence of buffering power in giant fused cells from frog kidney proximal tubule.

This study measures the intrinsic buffering power (beta(i)) of giant fused cells from the proximal kidney tubule of the frog (Rana ridibunda) as a function of intracellular pH (pHi). We monitored pHi and transmembrane potential difference during acid or alkaline cell loading, achieved by removal of NH4Cl-containing solutions or CO2-HCO3(-)-equilibrated solutions, respectively, in the absence of extracellular Na+. Data were well fit by the equation for a single, monoprotic buffer with a maximum beta(i) at a pHi of 7.39 +/- 0.06 and a total buffer concentration of 30.7 +/- 1.6 mM (means +/- SD). From pHi measurements obtained during CO2-HCO3- exposure, we also calculated the buffering power afforded by the CO2-HCO3- pair, and we show its increasing contribution to total buffering power at increasing PCO2 and pHi. To our knowledge, this is the first report of a cell type in which intrinsic cell buffers can be adequately approximated as a single monoprotic buffer with a negative logarithm of apparent dissociation constant in the normal physiological range and essentially symmetric dependence on pHi in both acid and alkaline ranges.

Ammonium Chloride↗
PubMed2004

Liquid growth hormone: preservatives and buffers.

Growth hormone (GH) treatment is a successful medical therapy for children and adults with GH deficiency as well as for growth retardation due to chronic renal disease, Turner syndrome and in children born small for gestational age. For all of these conditions, treatment is long term and patients receive daily subcutaneous injections of GH for many years. Patient compliance is therefore of critical importance to ensure treatment benefit. One of the major factors influencing compliance is injection pain. Besides the injection device used, pain perception and local tissue reaction following injection are dependent on the preservative used in the formulation and the concentration of GH. Injection pain may also be related to the buffer substance and injection volume. A liquid formulation of GH, Norditropi SimpleXx, has been developed that dispenses with the need for reconstitution before administration. The formulation uses phenol (3 mg/ml) as a preservative (to protect product from microbial degradation or contamination) and histidine as a buffer. Alternative preservatives used in other GH formulations include m-cresol (9 mg/ml) and benzyl alcohol (3-9 mg/ml). Buffering agents include citrate and phosphate. Phenol has been successfully used as a preservative in drug formulations for more than 50 years and is considered a safe and effective agent which complies with strict international requirements for preservatives in drug formulations. In toxicological studies, no or only mild local reactions have been observed following subcutaneous administration of phenol (7.5 mg/ml), m-cresol (3-4 mg/ml) and benzyl alcohol (9 mg/ml). No general toxicity reactions were observed after subcutaneous administration of these agents. Clinical evaluation of the preservatives and buffers used in Norditropin SimpleXx showed that pain perception was similar between formulations containing phenol and benzyl alcohol, whereas m-cresol was associated with more painful injections than benzyl alcohol. Furthermore, patients reported more pain following injection of a citrate-buffered solution than after a histidine-buffered solution. More pain was also reported following large volume injections and following injections with solutions containing high protein concentrations. In summary, optimization of the preservative and buffer content of a liquid GH formulation may reduce injection pain and lead to improved patient compliance.

Buffers↗
PubMed2003

The acid-base effects of continuous hemofiltration with lactate or bicarbonate buffered replacement fluids.

OBJECTIVE: To evaluate, quantify and compare the effects of continuous veno-venous hemofiltration (CVVH) with lactate or bicarbonate-buffered replacement fluids on acid-base balance. DESIGN: Randomized double crossover study. SETTING: Intensive Care Unit of Tertiary Medical Center. PARTICIPANTS: Eight patients with severe acute renal failure. INTERVENTIONS: Random allocation to either 2 hours of isovolemic lactate-buffered (treatment A) CVVH or 2 hours of bicarbonate-buffered (treatment B) CVVH with cross over and with same procedure repeated the following day (double cross over). MEASUREMENTS AND RESULTS: Timed collections of arterial blood and ultrafiltrate (UF), measurement of blood and UF gases and lactate concentrations and calculation of buffer-base mass balance. At baseline, both groups of patients had a similar, slight metabolic alkalosis (pH: 7.45 vs. 7.45; BE 3.9 mEq/L for treatment A and 4.0 for treatment B) and a serum bicarbonate of 28.1 mmol/L for treatment A vs. 28.3 mmol/L for treatment B; all NS. This alkalosis was present despite slight hyperlactatemia in both groups (A: 2.4 mmol/L vs. B 2.8 mmol/; NS). Within 60 minutes of treatment, however, treatment A led to a significantly higher lactate concentration (3.9 vs 2.5 mmol/L; p = 0.0011), a significantly lower BE (2.3 vs 4.1 mEq/L; p = 0.0019) and a significantly lower bicarbonate concentration (26.7 vs. 28.3 mmol/L; p = 0.0038) in the presence of an unchanged PaCO2. These differences persisted during the study period. The UF of patients receiving treatment A contained more lactate (10.2 vs 2.9 mmol/L; p < 0.0001) and less bicarbonate (25.6 vs. 30.8 mmol/L; p < 0.0001) than treatment B resulting in a mean buffer-base balance of +20.4 mEq/h compared to -2.6 mEq/h for treatment B; p < 0.0001). CONCLUSIONS: CVVH with lactate-buffered replacement fluids induces iatrogenic hyperlactatemia. Such hyperlactatemia is associated with an acidifying effect despite a positive buffer-base balance.

Acid-Base Equilibrium↗
PubMed2003

Factors affecting the microclimate pH of the rat jejunum in ringer bicarbonate buffer.

General characteristics of the microclimate layer on the mucosal surface of the rat jejunum incubated in bicarbonate buffers were investigated in vitro using pH sensitive flat membrane microelectrode. Jejunal surface microclimate (JSM) pH changed from 7.30+/-0.03 to 5.83+/-0.04 when the incubation buffer pH decreased from 8.03+/-0.02 to 6.12+/-0.01. Treatment of the mucosal side with mucolytic substances L-cysteine (1% (wt/v)) and 1,4-dithio-DL-threitol (2 mM) significantly (p<0.01) increased JSM pH. Respiratory chain inhibitor, sodium azide (10 mM) also significantly (p<0.05) increased JSM pH. D-Glucose (10 mM) at the mucosal side markedly (p<0.05) decreased JSM pH, which was attenuated by Na(+)/H(+) exchange inhibitor, amiloride (1 mM). Amiloride had no effect on JSM pH when D-glucose was not present at the mucosal side. In contrast to previous observations using bicarbonate free incubation buffers, we have demonstrated that JSM pH is not a constant value, but is dependent on pH of the incubation buffer. Additionally, Na(+)/H(+) exchanger does not contribute to acidic properties of JSM, when there is no D-glucose in the bicarbonate incubation buffer at the mucosal side of the tissue. In conclusion, we suggest that the bicarbonate buffers which are more close to in vivo situation than bicarbonate free buffers should be preferable incubation media when examining JSM.

Amiloride↗
PubMed2002

A single buffer that universally serves both restriction digestion and loading.

Restriction digestion is routinely performed in a buffer compatible with the restriction enzyme used. To load the samples on agarose gels for electrophoresis it is then necessary to add a loading buffer. A 10X loading buffer is often used, and consists of a dye to track the electrophoresis and a dense solution so that the digestion mixture sinks into the well. We describe a new buffer, which acts as a universal digestion buffer as well as a loading buffer. This avoids double handling of samples, which wastes both time and consumables. Importantly, the efficiency of digestion was found not to be significantly decreased in this new buffer.

Buffers↗
PubMed1986

Buffering capacity of some Nigerian food-substances.

The buffering capacity of some Nigerian local food substances was investigated using a modification of Toveys method (1974), Beans (red, and white), maize, rice (unprocessed with hull) and rice (unpolished) appeared to have high buffering capacity while yam, cassava and polished rice all showed weak buffering capacity. According to the analysis of Nigeria's foods and food-stuffs by Oyenuga, (1968)2 the former group of food substance incidentally have high phosphorus contents and relatively higher iron, calcium and protein contents. (The index of the buffering capacity is the number of millitres of acid that was mopped up before attaining pH 1.9). The buffering capacity was prominent at a higher pH range in the strong buffers than in the weak ones. This study would therefore encourage ulcer patients to eat more of beans especially the red type since it showed the greatest buffering capacity.

Buffers↗
PubMed1994

Effects of buffer pH and phosphate concentration on the droplet size and EYP hydrolysis of perflubron/EYP emulsions.

Oil-in-water emulsions containing perflubron (perfluorooctyl bromide; PFOB) and stabilized with egg yolk phospholipid (EYP) have potential applications as contrast agents and oxygen carriers. In this study, the effects of buffer pH and total phosphate concentration on the emulsion droplet size and EYP hydrolysis were evaluated. 90% w/v perflubron emulsions with NaH2PO4-Na2HPO4 buffers of different pH (4.7-8.7) and phosphate concentrations (30 and 60 mM) were prepared with a high-pressure homogenizer. Emulsions were stored at 40 degrees C and tested at 0, 1, 2 and 3 months. The pH dropped quickly in emulsions with pH 8.7 buffer whereas acidic and neutral buffered emulsions exhibited minor pH drops. The concentration of free fatty acids (FFA) vs emulsion pH can be fitted to a parabolic curve with a minimum at about pH 6.0. The droplet growth rates in emulsions with the pH 4.7 buffer were about 2.5 times of those in emulsions with the pH 8.7 buffer. Total phosphate concentration had only a minor effect. This study emphasizes the importance of the careful selection of buffer pH and capacity to control EYP hydrolysis and possibly emulsion droplet size.

Buffers↗
PubMed2001

Influence of carbohydrate source and buffer on rumen fermentation characteristics, milk yield, and milk composition in late-lactation Holstein cows.

The effects of concentrate-to-forage ratio and buffer on rumen fermentation and production parameters were examined in four rumen-cannulated cows (240 +/- 18 d in milk) fed a total mixed ration ad libitum in a 4 x 4 Latin square design. The treatments were a 50:50 concentrate to forage ratio with [1.2% of dry matter, (DM)] and without (0% of DM) buffer and a 75:25 concentrate to forage ratio with (1.2% of DM) and without (0% of DM) buffer. Rumen pH declined in response to increased concentrate but was not influenced by buffer. In the absence of the buffer, rumen acetate declined and propionate was elevated at the higher level of concentrate inclusion. The milk fat concentration was lower for cows fed the high concentrate diet without buffer; however, the addition of buffer to the diet prevented the milk fat depression. Milk fat depression was associated with elevated trans-C18:1 fatty acids in milk, which provides additional support for an inhibitory effect of these fatty acids on mammary fat synthesis. We concluded that the potential of nutrition as a tool to alter milk composition is greater in later lactation as these animals are better able to cope with the negative effects of high grain diets, and the treatment response is greater than in early lactation.

Acetates↗
PubMed1985

Addition of buffers to high quality alfalfa hay-based diets for dairy cows in early lactation.

Beginning 4 wk postpartum, 14 Holstein cows were paired according to expected calving date and lactation number and assigned randomly to one of two treatments in a single reversal experiment designed to study the effects of added buffers to high quality alfalfa hay-based diets. Cows were offered daily 14.5 kg of concentrate containing 0 or 2% sodium bicarbonate and .5% magnesium oxide (as fed), plus free choice high quality alfalfa hay in a ratio of forage:grain approaching 50:50 (dry matter). No differences were in milk production, milk fat percentage, fat-corrected milk, or dry matter intake. Dry matter intake of grain was decreased with addition of buffers. Kilograms fat-corrected milk per kilogram of dry matter intake were 1.41 and 1.45 for control and buffered diets. No differences were significant for rumen pH, ammonia concentration, molar proportions of acetate and propionate, or ratio of acetate: propionate. Concentrations of total volatile fatty acids were higher for cows fed the buffered diet. No differences were in blood acid-base status or in various serum metabolites. Urine pH was 8.11 and 8.20 for control and buffered diets. Fractional urinary excretion of magnesium and sodium was greater when cows consumed the buffered diet. Diet digestibilities and rate of passage were not affected by dietary buffers. Addition of sodium bicarbonate plus magnesium oxide did not improve performance of early lactation cows fed high quality alfalfa hay as the sole forage.

Animal Feed↗
PubMed1999

Lactate- or bicarbonate-buffered solutions in continuous extracorporeal renal replacement therapies.

BACKGROUND: Continuous renal replacement therapies (CRRTs) are well accepted for critically ill patients with acute renal failure (ARF). Today, daily fluid exchange in CRRT reaches 30 to 40 liter and more. Therefore, the composition of the substitution/dialysate fluid, often primarily developed either for intermittent treatment or for peritoneal dialysis, becomes more relevant. Lactate (30 to 45 mmol/liter) is frequently used as the buffer because of the high stability of this substance. However, lactate is thought to have negative effects on metabolic and hemodynamic parameters. METHODS: Published data for different substitution fluids are presented with respect to acidosis and lactate concentration, uremia, and hemodynamic and metabolic alterations. RESULTS: Only a few studies compare substitution fluids with different buffers. Uremia and acidosis (pH, base excess) were sufficiently controlled during CRRT with an exchange volume of in average 30 liters using either buffer. If patients with severe liver failure and lactic acidosis were excluded, no difference in hemodynamic and metabolic parameters between the solutions occurred. The plasma lactate concentration was elevated during lactate use in some cases, but lactate levels remained within normal limits in patients without liver impairment. The bicarbonate concentration in the solutions should exceed 35 to 40 mmol/liter, as in some cases the buffer capacity of the solutions was inadequate. In patients with severe liver failure or lactic acidosis, solutions with lactate buffer were shown not to be indicated. CONCLUSION: In patients with reduced lactate metabolism, for example, concomitant severe liver failure, after liver transplantation or in lactic acidosis, bicarbonate-buffered solutions should be used. In nearly all other cases of critically ill patients with ARF, lactate-buffered solutions may be used as well as bicarbonate solutions.

Acute Kidney Injury↗
PubMed2001

Automatic buffer capacity model building for the purpose of water quality monitoring.

In this paper, buffer capacity profiles are used in the framework of automatic monitoring of water quality. The aim of the proposed methodology is to automatically and stepwise build buffer capacity models for each particular titrated sample, and to quantify the individual buffer systems that constitute the total buffer capacity. An automatic and robust model building algorithm has been developed and applied to many titration curves of effluent and river water samples. It is illustrated that the application of automatically built buffer capacity models mostly results in similar or better estimations of ammonium and ortho-phosphate in the samples compared to a priori fixed buffer capacity models. The automatic modelling approach is also advantageous for alarm generating purposes on e.g. river waters, because unexpected buffers are easily detected.

Automation↗
PubMed1983

Isolation buffer calcium concentration and subsequent acute effects of insulin on metabolism of perfused rat liver.

During the surgical isolation for subsequent perfusion in situ with blood containing 1.3 mM Ca, livers from fed male rats were perfused with buffer containing 1.3 or 3.6 mM Ca. Total liver Ca was unaffected by buffer concentration and did not differ from non-perfused controls. In all groups a negative relationship was found between serum Ca and K+ concentrations and serum K+ was depressed by insulin and high buffer Ca while serum Ca was raised by the latter. Blood glucose was raised by isolation at high buffer Ca but was lowered by insulin with an increase in liver glycogen in both groups. Ketogenesis was unaffected by buffer Ca and was inhibited by insulin. The hormone raised serum triacylglycerol secretion and liver triacylglycerols in both groups, but the latter increase was abolished at the higher buffer Ca concentration. This effect on liver triacylglycerols may be related to the rise in microsomal Ca-ATPase activity found in these livers. We conclude that use of high concentrations of Ca in the isolation buffer, which may maintain hormone sensitivity in isolated hepatocytes, is not advantageous to the subsequent perfusion of the isolated liver with undiluted blood.

Animals↗
PubMed1997

Mechanisms and effects of intracellular calcium buffering on neuronal survival in organotypic hippocampal cultures exposed to anoxia/aglycemia or to excitotoxins.

Neuronal calcium loading attributable to hypoxic/ischemic injury is believed to trigger neurotoxicity. We examined in organotypic hippocampal slice cultures whether artificially and reversibly enhancing the Ca2+ buffering capacity of neurons reduces the neurotoxic sequelae of oxygen-glucose deprivation (OGD), whether such manipulation has neurotoxic potential, and whether the mechanism underlying these effects is pre- or postsynaptic. Neurodegeneration caused over 24 hr by 60 min of OGD was triggered largely by NMDA receptor activation and was attenuated temporarily by pretreating the slices with cell-permeant Ca2+ buffers such as 1, 2 bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid acetoxymethyl ester (BAPTA-AM). This pretreatment produced a transient, reversible increase in intracellular buffer content as demonstrated autoradiographically using slices loaded with 14C-BAPTA-AM and by confocal imaging of slices loaded with the BAPTA-AM analog calcium green-acetoxymethyl ester (AM). The time courses of 14C-BAPTA retention and of neuronal survival after OGD were identical, indicating that increased buffer content is necessary for the observed protective effect. Protection by Ca2+ buffering originated presynaptically because BAPTA-AM was ineffective when endogenous transmitter release was bypassed by directly applying NMDA to the cultures, and because pretreatment with the low Ca2+ affinity buffer 2-aminophenol-N,N,O-triacetic acid acetoxymethyl ester, which attenuates excitatory transmitter release, attenuated neurodegeneration. Thus, in cultured hippocampal slices, enhancing neuronal Ca2+ buffering unequivocally attenuates or delays the onset of anoxic neurodegeneration, likely by attenuating the synaptic release of endogenous excitatory neurotransmitters (excitotoxicity).

Animals↗
PubMed1994

Relative functional buffering capacity in 400-meter runners, long-distance runners and untrained individuals.

Buffering is a factor which influences performance in short and middle-term endurance by compensating exercise acidosis. The aim of the study was to establish whether respiration parameters are a relative measure of buffering capacity and to study the influence of buffering on specific performance parameters. Three groups (each of ten subjects) with defined degrees of adaptation [untrained (UT), aerobic-trained (AeT) and elite 400-m runners (AnT) with a best time of 48.47 +/- 0.98 s] were examined in an incremental multi-stage test on the treadmill. Breath-by-breath gas analysis was performed using mass spectrometry and computer routines. Serum lactate concentrations were determined at each exercise level until subjective exhaustion. A value for the relative functional buffering capacity (relFB) was calculated using exercise metabolic parameters. Running speed at the lactate threshold was used as the starting point of buffering. The start of respiratory compensation of acidosis (RCP) was taken as the endpoint of buffering. RCP was determined at the point of decrease in end-tidal CO2 content (CO2-ET). RelFB was given in percent of buffering to running speed at RCP. Group AnT attained the same maximum performance data (maximum running speed, maximum rate of O2 consumption) as group AeT. However, these values were attained in group AnT with a significantly higher relFB (AnT: 31.0 +/- 3.2% vs. AeT: 15.7 +/- 3.9%, P < 0.0001), while a higher lactate threshold indicated a greater oxidative capacity in AeT (AeT: 3.07 +/- 0.26 m.s-1 vs. AnT: 2.68 +/- 0.22 m.s-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

In vitro evaluation of phosphate, bicarbonate, and Hepes buffered storage solutions on hypothermic injury to immature myocytes.

In this study we evaluated cardiac myocyte viability and function under hypothermic conditions using three types of buffer solutions: phosphate buffer solution (PBS), Krebs-Henseleit bicarbonate buffer solution (KHB), and Hepes buffered minimum salt solution (MSS). As a control, normal saline solution (NSS) was used. Cardiac myocytes were isolated from neonatal rat ventricles. Myocytes (12.5 x 10(5) myocytes/culture flask) were then incubated at 4 degrees C for 6, 12, 18, and 24 hours in various buffer solutions. After each incubation time, CPK and LDH were measured. The myocytes were then incubated for an additional 24 hours at 37 degrees C to evaluate the recovery of the myocyte beating rate. Group MSS had a significantly better beating rate recovery than group NSS (control) after 18 hours (MSS, 32.7%, NSS, 0.0% of control; i.e., beating rate prior to hypothermic incubation). In contrast, group KHB showed a significantly lower recovery ratio than group NSS at 12 hours (41.0%, 78.8%, respectively), and the lowest recovery was observed in group PBS beginning at 6 hours of hypothermic incubation (27.6%). Group MSS significantly suppressed the release of CPK and LDH compared to group NSS at 24 hours (MSS, 246.7 and 440.2 mIU/flask; NSS, 369.7 and 821.3 mIU/flask, respectively). In contrast, groups PBS and KHB showed significantly increased CPK and LDH levels compared to group NSS after 12 hours (PBS, 388.6 and 721.4 mIU/flask; KHB, 340.5 and 540.5 mIU/flask; NSS, 91.5 and 222.7 mIU/flask, respectively). In conclusion, Hepes buffer has cytoprotective characteristics that may be suitable for long-term hypothermic preservation of immature myocardium compared to phosphate or bicarbonate buffer.

Animals↗
PubMed2002

Adipose tissue as a buffer for daily lipid flux.

Insulin resistance occurs in obesity and Type II (non-insulin-dependent) diabetes mellitus, but it is also a prominent feature of lipodystrophy. Adipose tissue could play a crucial part in buffering the flux of fatty acids in the circulation in the postprandial period, analogous to the roles of the liver and skeletal muscle in buffering postprandial glucose fluxes. Adipose tissue provides its buffering action by suppressing the release of non-esterified fatty acids into the circulation and by increasing triacylglycerol clearance. In particular, the pathway of 'fatty acid trapping' (adipocyte uptake of fatty acids liberated from plasma triacylglycerol by lipoprotein lipase) could play a key part in the buffering process. If this buffering action is impaired, then extra-adipose tissues are exposed to excessive fluxes of lipid fuels and could accumulate these in the form of triacylglycerol, leading to insulin resistance. These tissues will include liver, skeletal muscle and the pancreatic beta cell, where the long term effect is to impair insulin secretion. Adipose tissue buffering of lipid fluxes is impaired in obesity through defects in the ability of adipose tissue to respond rapidly to the dynamic situation that occurs after meals. It is also impaired in lipodystrophy because there is not sufficient adipose tissue to provide the necessary buffering capacity. Thus, the phenotype, at least with regard to insulin resistance, is similar with both excess and deficiency of adipose tissue. Furthermore, this concept could provide a framework for understanding the action of the thiazolidinedione insulin-sensitizing agents.

Adipose Tissue↗
PubMed1984

Leukotriene D4 elicits a non-sustained contraction of the guinea pig trachea in calcium-free buffer.

The contraction of the isolated guinea pig trachea elicited by leukotriene D4 (LTD4) in Ca2+-free buffer (containing 10(-4) M EGTA) achieved a maximum at 6-8 min and relaxed back to baseline approximately 25 min after challenge with LTD4. In contrast, LTD4 elicited a sustained contraction in the presence of 1.8 mM calcium. This sustained contraction in the presence of calcium was reproduced upon repeated LTD4 challenge, whereas in Ca2+-free buffer, only one LTD4-induced contraction could be obtained. The amplitude of the LTD4-induced contraction in Ca2+-free buffer decreased in a time-dependent manner which was also dependent upon the concentration of LTD4. At 10(-7) and 10(-6) M LTD4, small contractions (11% and 20% of control, respectively) were measured after 30 min in Ca2+-free buffer, whereas 10(-8) M LTD4 elicited a contraction at 15 min but not after 30 min in Ca2+-free buffer. Whereas washing the trachea for 5 min with LaCl3 (1.8 mM) only partially suppressed the LTD4-induced contraction in the presence of calcium, the contraction elicited by LTD4 in Ca2+-free buffer was not affected by LaCl3. The LTD4-induced contraction in Ca2+-free buffer was not affected by verapamil (10(-6) M); in contrast, the putative intracellular calcium antagonist, TMB-8 (10(-4) M), blocked the LTD4-induced contraction. These results provide evidence that the release of an intracellular calcium store plays an important role in the initiation of the LTD4-induced contraction of the guinea pig trachea. In addition, these results suggest that an extracellular calcium source may account for a small part of the LTD4-induced contraction.

Airway Resistance↗