Role of macula densa adenosine triphosphate (ATP) in tubuloglomerular feedback

BACKGROUND: Recent studies have shown that adenosine triphosphate (ATP) is liberated from macula densa cells in response to increased tubular NaCl in vitro. We tested the hypothesis that increased NaCl in the macula densa stimulates the release of ATP, resulting in extracellular formation of adenosine which is involved in signal transmission of the tubuloglomerular feedback response. METHODS: Rabbit afferent arterioles and attached macula densas were simultaneously microperfused in vitro. Tubuloglomerular feedback was induced by increasing macula densa Na/Cl from 11/10 to 81/80 mmol/L and was measured before and after treatment. RESULTS: We first tested whether hydrolysis of ATP is required for tubuloglomerular feedback. When we enhanced conversion of ATP to adenosine by adding hexokinase or apyrase to the bath and arteriole lumen, the tubuloglomerular feedback response was augmented. During the control period, tubuloglomerular feedback decreased arteriole diameter by 2.2 +/- 0.2 microm. In the presence of hexokinase, tubuloglomerular feedback decreased diameter by 3.4 +/- 0.3 microm (N= 8) (P < 0.05, with vs. without hexokinase). In the apyrase group, tubuloglomerular feedback decreased diameter by 2.7 +/- 0.4 microm during the control period. When apyrase was added, tubuloglomerular feedback decreased diameter by 4.7 +/- 0.4 microm (N= 8) (P < 0.05, with vs. without apyrase). When hydrolysis of adenosine monophosphate (AMP) to adenosine was blocked by supplementing the bath with 100 micromol/L alpha,beta-methylene adenosine 5'-diphosphate (MADP), an inhibitor of 5'-nucleotidase, tubuloglomerular feedback response was blocked and diameter remained unchanged. We next studied whether ATP released from the macula densa binds to P(2) receptors and activates the tubuloglomerular feedback response. The P(2) purinergic receptor inhibitor suramin was added to both arteriole lumen and bath. During the control period, tubuloglomerular feedback decreased diameter by 3.7 +/- 0.5 microm. Suramin (100 micromol/L) did not significantly inhibit tubuloglomerular feedback, since in the presence of suramin diameter decreased by 3.8 +/- 0.3 microm (N= 7). Finally, we added the adenosine A(1) receptor inhibitor FK838 to both bath and lumen and found that it completely blocked high NaCl-induced tubuloglomerular feedback. CONCLUSION: We concluded that ATP released from the macula densa is broken down to form AMP in the extracellular space. AMP in turn is degraded by ecto-5'-nucleotidases to adenosine, which mediates signal transmission of the tubuloglomerular feedback response.     

The effect of hypothermia on liver adenosine triphosphate (ATP) recovery following combined shock and ischemia.

During both hemorrhagic shock and ischemia, adenosine triphosphate (ATP) concentrations fall in liver tissue. Incomplete recovery of ATP correlates with cell death and subsequent organ dysfunction. Changes in liver ATP levels were evaluated in paired groups of rats subjected to combined hemorrhagic shock and ischemia. A second set of paired animals was studied over time with shock alone. One animal in each pair was maintained at 28 degrees C and the other at 37 degrees C. Ischemia was produced by occluding inflow to the left half of the liver, and tissue was obtained from this area in all animals studied. Adenosine triphosphate levels fell in warm and cold animals subjected to both shock and 60 minutes of ischemia but recovered more completely during reperfusion in the cold animals. Shock alone caused a steady fall in ATP levels in the warm, but not the cold rats. These biochemical changes may indicate a beneficial effect of moderate hypothermia in the management of severe liver hemorrhage requiring temporary occlusion of blood flow.     

Permeability of red-cell membrane to adenosine triphosphate (ATP) molecules during hemorrhagic shock

The findings of decreased adenosine triphosphate (ATP) levels in liver, kidney, and other tissues of animals in hemorrhagic shock were the rationale for previous experimental attempts to improve cell function by administration of fluids that contained high concentrations of ATP. The beneficial effects of this resuscitation, which are still controversial, were attributed to cellular uptake of ATP--it was assumed that cell membranes are permeable to this substrate. The effect of a high concentration of ATP in extracellular medium on intracellular ATP content was studied by using red blood cells (RBCs) from rabbits in control (normal) and in hemorrhagic shock states. The glucose-depleted RBCs were incubated in medium with 5 mMol/L ATP, and their ATP concentration fell markedly to the same level as seen in glucose-depleted RBCs incubated without ATP. The decrease of ATP in glucose-repleted RBCs, incubated with or without ATP, also did not show any significant difference. Similar to parallel experiments that used normal RBCs, the high extracellular ATP content did not substantially affect the intracellular ATP concentration in RBCs from animals in shock. This study indicates that ATP molecules in extracellular medium cannot penetrate either the normal RBC membrane or the RBC membrane during shock.     

Adenosine triphosphate (ATP) in human spermatozoa

The seminal adenosine triphosphate (ATP) content was determined by bioluminescence after treatment with trichloroacetic acid (TCA) in 81 semen samples 1.5 h after ejaculation obtained from men attending our fertility clinic, and selected to contain either 20% or less spermatozoa with good progressive motility (n = 22), or 60% or more spermatozoa with good progressive motility (n = 59) (Study I), and in 18 semen samples from fertile men 30 min and 3.5 h after ejaculation (Study II). The latter samples were divided into 2 equally large groups according to sperm motility. In Study I the mean sperm ATP concentration was significantly higher in the semen samples with bad motility (0.63 nmol per living spermatozoa x 10(-6)) than in semen samples with good motility (0.39 nmol per living spermatozoa x 10(-6); P less than 0.01). In Study II the ATP concentration per living spermatozoa was also lower in the group with the best motility in comparison with the spermatozoa with lower motility (P less than 0.01), both 30 min and 3.5 h after ejaculation. During the 3-5 h incubation the sperm ATP concentration decreased by 21% (P less than 0.01) in the former group of samples but remained unchanged in the latter group. The results indicate that, in semen samples with highly motile spermatozoa, the consumption of ATP is higher than in semen samples with impaired sperm motility. It is therefore essential that the time between ejaculation and ATP measurement is as short as possible to obtain comparable results. Repeated ATP measurements in combination with an analysis of the number of living spermatozoa, may provide further information on the fertilizing capacity of spermatozoa.     

Effects of adenosine triphosphate (ATP) on somatosensory evoked potentials in humans anesthetized with isoflurane and nitrous oxide

In order to examine the usefulness of adenosine triphosphate (ATP) as an adjuvant to anesthesia for surgery requiring intraoperative somatosensory evoked potential (SSEP) monitoring, we have studied the effects of ATP on SSEPs in patients anesthetized with isoflurane and nitrous oxide (N₂O). A control recording of SSEP was performed while anesthesia was maintained with 0.5% end-tidal concentration of isoflurane in 60% N₂O. The recordings were repeated after an ATP infusion had been added to this basal anesthesia at the rates of 100 μgkg bw^-1 min^-1 and 200 μg kg bw^-1 min^-1. SSEP was also studied when end-tidal isoflurane concentration was increased to 1.5% after cessation of ATP infusion. An infusion of ATP combined with 0.5% isoflurane and 60% N₂O effectively inhibited an increase in blood pressure during surgery. The amplitude of the cortical component of SSEP was lowered by 1.5% isoflurane, which also increased both cortical and spinal latencies as well as central conduction time (CCT). In contrast ATP infusions at both rates induced no significant changes in latencies, amplitude and CCT. The results indicate that ATP infusion combined with 0.5% isoflurane in 60% N₂O can be a useful anesthetic technique for intraoperative SSEP monitoring because adequate anesthetic depth can be maintained by a low concentration of anesthetics without further suppression of SSEPs.     

The diagnostic value of seminal adenosine triphosphate (ATP) in an in vitro fertilization (IVF) program: Der diagnostische Wert von ATP in einem IVF-Programm

The level of adenosine triphosphate (ATP) was quantitated in semen samples used for in vitro fertilization of human oocytes. Seminal ATP level correlated with the concentration and percentage motility of spermatozoa but not with the in vitro fertilization rate of human oocytes. Seminal ATP measurement appears to have little diagnostic value in predicting the fertilizing capacity of spermatozoa as evaluated by the multivariate stepwise discriminant analysis.     

Reassessment of the accuracy of traditional sperm characteristics and adenosine triphosphate (ATP) in estimating the fertilizing potential of human semen in vivo

Receiver operating characteristic curves and accuracy parameters were computed for traditional sperm characteristics (concentration, motility, morphology) and the number of peroxidase negative cells, and the concentration of adenosine triphosphate (ATP) in semen from populations of fertile and infertile men, and men who achieved a pregnancy after varicocele treatment. The percentage and concentration per millilitre of spermatozoa with rapid linear progressive motility, and the ATP concentration, provided the best discrimination between fertile and treated fertile from infertile men. The misclassification rate was higher for sperm morphology, total progressive motility and viability, whereas sperm concentration and the total sperm count per ejaculate had the worst discriminating power. The number of peroxidase negative cells per 100 spermatozoa was highly specific in identifying men who achieved pregnancy after varicocele treatment. The lower limit of normality of sperm characteristics was remarkably different between fertile men and men achieving pregnancy after treatment or during infertility work-up.     

Potential value of adenosine 5'-triphosphate (ATP) and adenosine in anaesthesia and intensive care medicine

Extracellular adenosine and adenosine triphosphate (ATP) areinvolved in biological processes including neurotransmission,muscle contraction, cardiac function, platelet function, vasodilatation,signal transduction and secretion in a variety of cell types.They are released from the cytoplasm of several cell types andinteract with specific purinergic receptors which are presenton the surface of many cells. This review summarizes the evidenceon the potential value and applicability of ATP (not restrictedto ATP–MgCl₂) and adenosine in the field of anaesthesiaand intensive care medicine. It focuses, in particular, on evidenceand roles in treatment of acute and chronic pain and in sepsis.Based on the evidence from animal and clinical studies performedduring the last 20 years, ATP could provide a valuable additionto the therapeutic options in anaesthesia and intensive caremedicine. It may have particular roles in pain management, modulationof haemodynamics and treatment of shock.     

Adenosine-triphosphate in trauma-related and elective hypothermia.

BACKGROUND: In trauma patients, hypothermia is a frequent event. According to the literature, the majority of trauma patients are presenting a core temperature of less than 34 degrees C at admission. In contrast to the benefit of hypothermia in elective surgery, clinical experience with hypothermia in trauma patients has identified hypothermia to be one major cause of severe posttraumatic complications. It was hypothesized that this diverse effect of hypothermia is related to depletion of high-energy phosphates like adenosine triphosphate (ATP) in trauma patients. To verify this hypothesis, the relation of ATP plasma levels and hypothermia was examined in a clinical study. METHODS: Three different groups of patients were under study. The first group (group A, normothermic control group) included patients (n = 15) undergoing elective surgery of the lower limb with a mean operation time of 113 minutes. The second study group (group B, hypothermic control) was composed of patients (n = 15) who were subjected to elective coronary artery bypass operation under hypothermia (31 degrees C for 48 minutes, mean total operation time being 205 minutes). The third study group (group C) included trauma patients (n = 23, mean Injury Severity Score [ISS] of 24.7). At the time of admission, 10 patients presented a core temperature more than or equal to 34 degrees C (group C1, mean ISS, 25.2; mean T(A), 34.5 degrees C), 13 patients presented a T(A) less than 34 degrees C (group C2, mean ISS, 26.0; mean T(A), 32.9 degrees C). In both groups of surgical patients, the ATP plasma level was measured preoperatively, at 2, 4, and 24 hours postoperatively. For trauma patients, this measurement was performed at admission and 24 hours later. Within the same schedule, body core temperature was recorded and the clinical course was documented as well. RESULTS: Elective limb surgery in normothermic patients resulted only in a transient decrease in ATP plasma levels (preoperative, 87.8 micromol/dL; 4 hours postoperative, 52.0 micromol/dL). At 24 hours, the ATP plasma level (62.6 +/- 10.0 micromol/dL) has increased toward baseline level. Elective hypothermia in patients subjected to coronary bypass also resulted only in a transient decrease in ATP plasma levels. During the operation period, including hypothermia, the ATP plasma level was comparable (50.4 micromol/dL) to group A and also returned back toward normal values at 24 hours (58.2 micromol/dL). All trauma patients revealed a significant low ATP plasma level at admission compared with both control groups. Looking at subdivided groups the most significant drop in ATP plasma level (28.5 micromol/dL) was noted in patients presenting an initial core temperature less than 34 degrees C and ISS more than 30. Even 24 hours later, the ATP level of this subgroup was significantly diminished, despite a rise up to 44.4 micromol/dL. In contrast, only a moderate drop in ATP plasma concentration (59.2 micromol/dL) was noted in the group of T(A) more than or equal to 34 degrees C and ISS less than 20. This group revealed almost normal values (68.3 micromol/dL) 24 hours after trauma. In addition to hypothermia, the metabolic state, reflected by the plasma lactate levels, significantly influenced the ATP plasma levels, as high lactate levels were paralleled by low ATP levels. Also, the overall outcome was related to injury severity and hypothermia. CONCLUSION: Hypothermia in elective surgery, established by active cooling, preserves the ATP storage and maintains an aerobic metabolism, which both contribute to the beneficial effect of hypothermia in ischemia/reperfusion in cardiovascular surgery. However, in trauma patients hypothermia is caused by insufficient heat production due to utilization of ATP under anaerobic metabolic conditions. Low ATP plasma levels combined with hypothermia seem to be a predisposition for post-traumatic complications like organ failure.     

Adenosine triphosphate (ATP) concentrations and ATP/adenosine diphosphate ratios in human sperm of normospermic, oligospermic, and asthenospermic specimens and in their swim-up fractions: lack of correlation between ATP parameters and sperm creatine kinase concentrations.

The authors had previously found an inverse correlation between per sperm creatine phosphokinase activity and sperm concentrations in men. Because creatine phosphokinase is a key enzyme in sperm energy transport, the possible relationship of sperm creatine phosphokinase activity, sperm adenosine triphosphate (ATP) concentrations, sperm ATP/ADP (adenosine diphosphate) ratios, and computer-aided semen analysis sperm motility parameters were then studied. The ATP concentrations and ATP/ADP ratios, measured by high-pressure liquid chromatography in washed sperm, were similar in normospermic and oligospermic specimens (ATP: 123.1 +/- 21.6 vs. 90.0 +/- 24.5 pmol/10(6) sperm; ATP/ADP: 2.8 +/- 0.4 vs. 2.1 +/- 0.4, N = 32 and 17, mean +/- SEM), and in samples with normal and less than 40% sperm motility (ATP: 96.8 +/- 27.2 vs. 122.2 +/- 19.6 pmol/10(6) sperm; ATP/ADP: 2.4 +/- 0.5 vs. 2.8 +/- 0.4, n = 26 and 23). In the swim-up sperm fractions, which showed improved motility, the ATP concentrations, but not the ATP/ADP ratios, were lower than in the initial semen samples (ATP: 152.9 +/- 28.4 vs. 90.3 +/- 10.6 pmol/10(6) sperm, P less than 0.05; ATP/ADP: 3.3 +/- 0.5 vs. 3.9 +/- 0.7, N = 18 pairs of samples). This is consistent with our previous finding of a lower cytoplasmic content in sperm in swim-up fractions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of TNF-alpha in local surgical trauma-induced microvascular dysfunction

BACKGROUND/AIM: The aim of this study was to gain insight into the mechanisms of microvascular dysfunction after local surgical trauma. METHODS: The effect of anti-tumor necrosis factor (TNF)-alpha antibody (Ab) on microvascular function, including arteriolar diameter response, nutritive perfusion, leukocyte-endothelial cell interaction and endothelial integrity disruption, was studied in hamster skinfold chamber preparations using intravital fluorescence microscopy. RESULTS: Directly after the surgical procedure, arteriolar diameters were found to be markedly (p < 0.05) reduced, but recovered significantly at 8 h and reached plateau levels after 24 h. Surgical trauma further induced a strong inflammatory response characterized by a significant (p < 0.05) increase in leukocyte adherence to the endothelium of postcapillary venules. This inflammatory response was associated with an increase in microvascular permeability, indicating endothelial integrity disruption. Anti-TNF-alpha Ab had no significant effect on the surgical trauma-induced arteriolar vasomotor dysfunction; however, it effectively (p < 0.05) reduced venular leukocyte adherence and attenuated the increase in microvascular permeability. CONCLUSION: Our study indicates that arteriolar constriction, leukocyte-endothelial cell interaction and endothelial macromolecular leakage have to be considered as the characteristic microvascular response after local surgical trauma. It is conceivable that TNF-alpha plays a role in mediating the inflammatory response, but not the dysfunction of vasomotor control. Copyright Copyright 1999 S.Karger AG, Basel     

Adenosine triphosphate (ATP) treatment of hypoxic pulmonary hypertension (HPH): comparison of dose dependence in pulmonary and renal circulations

In this study we investigated the relationship between pulmonary and renal responses to a low dose infusion of adenosine triphosphate-magnesium chloride (ATP-MgCl2) in a newborn piglet model of hypoxic pulmonary hypertension (HPH). Three- to five-day-old piglets were cannulated for the measurement of pulmonary and systemic arterial pressure, pulmonary and renal artery flow, and urine output. The animals were then made hypoxic by ventilation with a mixture containing 10% oxygen, 4% CO2, and balance nitrogen. Serial infusions of ATP-MgCl2 at 0.01, 0.025, 0.05, 0.1, 0.5, and 1.0 mg/kg/min were compared to preinfusion hypoxia baselines. Hypoxia alone produced a significant elevation in pulmonary artery pressure (73%) and a reduction in pO2. All dose rates of ATP-MgCl2 greater than or equal to 0.05 mg/kg/min produced a significant decrease in mean pulmonary artery pressure. However, as baseline mean pulmonary artery pressure increased there was an increased sensitivity to ATP-induced vasodilation. Pulmonary artery flow did not change during ATP infusion, thus, the change in pulmonary vascular resistance accounted for the decrease in pulmonary artery pressure. In contrast to the response of the pulmonary vasculature, systemic pressure was significantly decreased only during the 1.0 mg/kg/min infusion. Renal blood flow decreased by 46% during hypoxia and decreased further only during the highest dose rate of ATP infused (i.e., 1.0 mg/kg/min). Creatinine clearance (Ccr) and fractional reabsorption of Na (FreNa) also fell during hypoxia, but were not further altered during all but the highest dose of ATP infused.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protective effects of adenosine triphosphate administration in burns.

The effects of intramuscular adenosine triphosphate (ATP) administration after thermal skin injury on the ATP content and morphology of the liver and heart were studied in male Sprague-Dawley rats. The results showed that exogenous ATP injected during the early post-burn period could restore the ATP content of the liver and heart to near normal values and modify the burn-related morphological alterations in the liver.     

Muscle contractures and adenosine triphosphate depletion in porcine malignant hyperthermia

This study compares several methods for diagnosing susceptibility to malignant hyperthermia, using two groups of Poland China swine narrowly defined as genetically susceptible or normal (five pigs each) depending respectively on their response to halothane or to halothane and succinylcholine. Vastus medialis muscle biopsies were excised under thiopental-N2O-O2 anesthesia and used for examination of (1) contracture responses to halothane, (2) contracture responses to caffeine and halothane-caffeine, and (3) adenosine triphosphate (ATP) depletion with and without halothane. All studies were performed in organ baths at 37 C. Halothane alone produced contractures in two susceptible and one normal preparation; caffeine always produced a contracture at lower concentrations in susceptible muscle; caffeine-halothane contractures in susceptible muscle occurred at lower mean caffeine concentrations, but there was some overlap of individual values; mean ATP depletion was greater in susceptible muscle, but with considerable overlap. Comparisons with the findings of others were hampered by use of absolute rather than comparative values for tension, e.g., grams, rather than grams per cross-sectional area or fraction of peak tension. Examination of the complete dose-response curve provided the best comparative information and caffeine was the consistent predictor of susceptibility.     

Cyclosporine-induced adenosine triphosphate depletion in murine T and B lymphocytes

Adenosine metabolism in C57BL/6 mouse spleen cells was studied. Adenosine triphosphate (ATP) levels in resting T cells were 26.9 +/- 3.4 ng/10(5) cells compared with 16.5 +/- 3.1 ng/10(5) cells in resting B cells. Cyclosporine (CSA) caused a prompt and severe ATP depletion in both T and B cells, which could be mitigated by the addition of adenosine. B cell ATP levels were returned to normal while T cell levels were only partially restored. The adenosine deaminase inhibitor erythro-9-(2 hydroxy-3 nonyl) adenine (EHNA) also caused ATP depletion in T and B cells, which could similarly be prevented in part by the addition of adenosine. However, when CSA and EHNA were combined, adenosine could no longer protect ATP pools and severe ATP depletion in T and B cells occurred. This suggests that CSA and EHNA affect different steps in the conversion of adenosine to ATP. Although both T and B cell ATP levels were affected by CSA, the ability of supplementary substrate to restore ATP levels to normal in B cells but not in T cells may explain the apparent selective effect of CSA impairing T cell functions with sparing of B cell functions. Furthermore, if causing ATP depletion is associated with immunosuppressive activity, EHNA may be useful in potentiating the immunosuppressive effects of CSA.     

Postoperative hypothermia and patient outcomes after elective cardiac surgery

Hypothermia after elective cardiac surgery is an important physiological abnormality and is associated with increased morbidity and mortality. The Australian and New Zealand intensive care adult patient database was studied to obtain the lowest and highest temperature in the first 24 h after surgery. Hypothermia was defined as core temperature < 36 °C; transient hypothermia as temperature < 36 °C that was corrected within 24 h; and persistent hypothermia as hypothermia that was not corrected within 24 h. Hypothermia occurred in 28,587 out of a total of 43,158 consecutive patients (66%) and was persistent in 111 (0.3%). Transient hypothermia was not independently associated with increased hospital mortality (OR = 0.9, 95% CI 0.8-1.1), whereas persistent hypothermia was associated with markedly increased risk of death (OR = 6.3, 95% CI = 3.3-12.0). Hypothermia is common in postoperative cardiac surgery patients during the first 24 h after ICU admission but, if transient, is not independently associated with an increased risk of death.     

The effect of adenosine triphosphate on vecuronium-induced neuromuscular block

Continuous IV adenosine triphosphate administration has been used during surgery in the expectation of analgesic and vasodilative effects. Because adenosine triphosphate inhibits neuromuscular transmission, we investigated whether the neuromuscular effect of vecuronium was enhanced by IV adenosine triphosphate in 29 patients randomly given either continuous IV adenosine triphosphate 0.1 mg.kg(-1).min(-1) or 0.9% NaCl when undergoing elective minor surgery. Anesthesia was induced and maintained with propofol. Neuromuscular monitoring was recorded from the adductor pollicis muscle using electromyography with train-of-four stimulation of the ulnar nerve. Vecuronium 25, 30, or 40 microg/kg was given and lag time, onset time, and maximum block were recorded. ED50 and ED95 values for each group were derived from least squares linear regression analysis. ED50 and ED95 values were 29 microg/kg and 44 microg/kg, respectively, for the adenosine triphosphate group and 26 microg/kg and 46 microg/kg, respectively, for the controls. Differences in lag time, onset time, and neuromuscular responses between the two groups were not statistically significant. A significantly larger number of patients in the adenosine triphosphate group showed hypotension (systolic blood pressure <80 mm Hg). Our results demonstrated that adenosine triphosphate 0.1 mg.kg(-1).min(-1) did not enhance the neuromuscular block induced by vecuronium.