Determination of aciclovir and ganciclovir in human plasma by liquid chromatography-spectrofluorimetric detection and stability studies in blood samples

A sensitive HPLC method has been developed for the assay of aciclovir and ganciclovir in human plasma, by HPLC coupled with spectrofluorimetric detection. Plasma (1000 microl), with 9-ethyl-guanine added as internal standard, is submitted to protein precipitation with trichloroacetic acid solution 20%. The supernatant, evaporated to dryness at 37 degrees C, is reconstituted in 100 microl of a solution of sodium heptanosulfonate 0.4% adjusted with acetic acid to pH 2.60 and a 30 microl volume is then injected onto a Nucleosil 100-5 microm C18 column. Aciclovir and ganciclovir are analysed by spectrofluorimetric detection set at 260 nm (excitation) and 380 nm (emission) using a gradient elution program with solvents constituted of acetonitrile and a solution of sodium heptanosulfonate 0.4% adjusted to pH 2.60. The calibration curves are linear between 0.1 and 10 microg/ml. The mean absolute recovery of aciclovir and ganciclovir are 99.2+/-2.5 and 100.3+/-2.5%, respectively. The method is precise (with mean inter-day C.V.s within 1.0-1.6% for aciclovir and 1.2-3.5% for ganciclovir), and accurate (range of inter-day deviations -1.6 to +1.6% for aciclovir and -0.4 to -1.4% for ganciclovir). The method has been applied in stability studies of ganciclovir in patients' blood samples, demonstrating its good stability in plasma at -20 degrees C and at room temperature. The distribution of ganciclovir and aciclovir in plasma and red blood cells was also investigated in vitro in spiking experiments with whole blood, which showed an initial drop of ganciclovir and aciclovir levels in plasma (about -25%) due to the cellular uptake of aciclovir and ganciclovir by red blood cells. The method has been validated and is currently applied in a clinical study assessing the ganciclovir plasma concentration variability after administration of valganciclovir in a population of solid organ transplant patients.     

Separation of heavy metals from water solutions at the laboratory scale

Separation of heavy metals from water may be done by sulphide precipitation. In order to make the metal sulphides more valuable for reuse, they should be as pure as possible. To separate the metals from each other during the precipitation process different parameters as pH, sulphide concentration and redox potential may be controlled. Adjustment of the redox potential to specific values results in separation of copper from cadmium even at the same pH. In the copper precipitation step 98.7 +/- 0.5% was precipitated and the remaining part was transferred to the cadmium precipitation step where 0.7 +/- 0.5% of the copper precipitated. The main part of cadmium (95.6 +/- 1.3%) was precipitated in the second step. These results show that it is possible to separate copper from cadmium by the use of redox potential control.     

Metabolic effects of induced alkalosis during progressive forearm exercise to fatigue.

Metabolic alkalosis induced by sodium bicarbonate (NaHCO(3)) ingestion has been shown to enhance performance during brief high-intensity exercise. The mechanisms associated with this increase in performance may include increased muscle phosphocreatine (PCr) breakdown, muscle glycogen utilization, and plasma lactate (Lac(-)(pl)) accumulation. Together, these changes would imply a shift toward a greater contribution of anaerobic energy production, but this statement has been subject to debate. In the present study, subjects (n = 6) performed a progressive wrist flexion exercise to volitional fatigue (0.5 Hz, 14-21 min) in a control condition (Con) and after an oral dose of NaHCO(3) (Alk: 0.3 g/kg; 1.5 h before testing) to evaluate muscle metabolism over a complete range of exercise intensities. Phosphorus-31 magnetic resonance spectroscopy was used to continuously monitor intracellular pH, [PCr], [P(i)], and [ATP] (brackets denote concentration). Blood samples drawn from a deep arm vein were analyzed with a blood gas-electrolyte analyzer to measure plasma pH, Pco(2), and [Lac(-)](pl), and plasma [HCO(3)(-)] was calculated from pH and Pco(2). NaHCO(3) ingestion resulted in an increased (P < 0.05) plasma pH and [HCO(3)(-)] throughout rest and exercise. Time to fatigue and peak power output were increased (P < 0.05) by approximately 12% in Alk. During exercise, a delayed (P < 0.05) onset of intracellular acidosis (1.17 +/- 0.26 vs. 1.28 +/- 0.22 W, Con vs. Alk) and a delayed (P < 0.05) onset of rapid increases in the [P(i)]-to-[PCr] ratio (1.21 +/- 0.30 vs. 1.30 +/- 0.30 W) were observed in Alk. No differences in total [H(+)], [P(i)], or [Lac(-)](pl) accumulation were detected. In conclusion, NaHCO(3) ingestion was shown to increase plasma pH at rest, which resulted in a delayed onset of intracellular acidification during incremental exercise. Conversely, NaHCO(3) was not associated with increased [Lac(-)](pl) accumulation or PCr breakdown.     

Simultaneous determination of aciclovir, ganciclovir, and penciclovir in human plasma by high-performance liquid chromatography with fluorescence detection

A fast, simple and selective HPLC method has been developed for the assay of aciclovir, ganciclovir, and penciclovir in human plasma by coupling HPLC with fluorescence detection. 200 microl plasma, with guanosine 5'-monophosphate as an internal standard, was subjected to protein precipitation with a 7% [v/v] aqueous perchloric acid solution. The 40 microl supernatant was injected into a Diamonsil-5 microm C18 column. Aciclovir, ganciclovir, and penciclovir, with solvents composed of methanol and 0.08% aqueous trifluoroacetic acid solution, were analysed by fluorescence detection at 260 nm (excitation) and 380 nm (emission) using a gradient elution program. The calibration curves of all three analytes were linear between 20 and 2000 ng/ml. The mean absolute recoveries of aciclovir, ganciclovir, and penciclovir were 93.91+/-1.20%, 97.42+/-0.75%, and 99.01+/-3.30%, respectively. The mean inter-day CVs for aciclovir, ganciclovir, and penciclovir, were within 1.29-7.30%, 1.00-5.53%, and 1.19-3.54%, respectively. The intra-day bias for aciclovir, ganciclovir, and penciclovir ranged from -2.01 to 6.33%, 1.81 to 7.37%, and 1.42 to 6.91%, respectively. The method has been validated and applied in pharmacokinetic studies in Chinese adult renal transplant patients.     

Effect of reduced uterine blood flow on fetal and maternal cortisol

We have measured the changes in fetal and maternal plasma concentrations of cortisol in relation to blood gases and percent oxygen saturation during 2- and 4-h episodes of reversibly reduced uterine blood flow in sheep between 120 days gestation and term. During that period of reduced uterine blood flow there was a significant decrease in fetal arterial percent oxygen saturation (SaO2), PO2 and pH. Fetal SaO2 decreased from 59.5 +/- 3.2% to 31.8% +/- 2.8% by 15 min, 32.9 +/- 2.9% by 60 min, and 33.5 +/- 2.9% by 120 min. Fetal PO2 decreased from 3.2 +/- 0.1 KPa to 2.0 +/- 0.2 KPa by 15 min, 2.2 +/- 0.2 KPa by 60 min and 2.3 +/- 0.1 KPa by 120 min. Fetal pH decreased from 7.36 +/- 0.01 to 7.30 +/- 0.03 by 15 min, 7.27 +/- 0.02 by 60 min and 7.25 +/- 0.03 by 120 min. During the period of reduced uterine blood flow, fetal plasma concentrations of cortisol increased from 37.1 +/- 10.8 nmol/l to 53.3 +/- 9.2 nmol/l by 15 min, 49.2 +/- 11.4 nmol/l by 60 min and 43.3 +/- 9.0 nmol/l by 120 min. The greatest percentage increase in fetal plasma concentrations of cortisol occurred in fetuses of 126-139 days gestation. There was no significant change in maternal blood gases, SaO2 or plasma concentrations of cortisol. These experiments demonstrate that there is a significant increase in fetal plasma concentrations of cortisol in response to reductions in uterine blood flow from as early as 120 days gestation.     

High-performance liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS) method for the simultaneous determination of diazepam, atropine and pralidoxime in human plasma

A high-performance liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS) procedure for the simultaneous determination of diazepam from avizafone, atropine and pralidoxime in human plasma is described. Sample pretreatment consisted of protein precipitation from 100microl of plasma using acetonitrile containing the internal standard (diazepam D5). Chromatographic separation was performed on a X-Terra MS C8 column (100mmx2.1mm, i.d. 3.5microm), with a quick stepwise gradient using a formate buffer (pH 3, 2mM) and acetonitrile at a flow rate of 0.2ml/min. The triple quadrupole mass spectrometer was operated in positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges of 1-500ng/ml for diazepam, 0.25-50ng/ml for atropine and 5-1000ng/ml for pralidoxime. The coefficients of variation were always <15% for both intra-day and inter-day precision for each analyte. Mean accuracies were also within +/-15%. This method has been successfully applied to a pharmacokinetic study of the three compounds after intramuscular injection of an avizafone-atropine-pralidoxime combination, in healthy subjects.     

Decrease of erythropoietin level by human recombinant tumour necrosis factor alpha (hrec TNFalpha) in patients with advanced cancer

Anaemia is a frequent complication of chronic inflammation, infectious diseases and cancer. Inappropriate erythropoietin production is regarded as one of the main causative factors responsible for the occurrence of anaemia. The pathogenesis of TNFalpha induced-anaemia has not been fully clarified yet and its influence on hematopoiesis has been suggested. We performed a clinical study to access the influence of hrec TNFalpha administration on plasma EPO concentration and the degree of anaemia in patients with advanced solid tumours for whom no other kind of therapy but palliative treatment was available. All these patients exposed mild anaemia (HT 36.1 +/- 1.0%). Plasma EPO was estimated at 8 a.m. before and after 5 days of TNFalpha therapy with a dose of 75 pg/day iv (cycle I). Two weeks later plasma EPO was estimated again before and after 5 days of TNFalpha administration of a double dose (150 microg/day) (cycle II). The control group comprised 8 non-cancer patients (5M/3F, age 48.5 +/- 6yr) with the same degree of anaemia (HT 36 +/- 1.1%) due to haemorrhage. In the control group the plasma EPO level was significantly higher (54.2 +/- 8 mU/ml) than in cancer patients before cycle I (17.1 +/- 2.5 mU/ml) and II (14.6 +/- 3.8 mU/ml) respectively.TNF administration was followed by a significant decline of plasma EPO both after the first (17.1 +/- 2.5 vs 9.0 +/- 1.5 mU/ml) and second cycle (14.6 +/- 3.8 vs 8.4 +/- 2.0 mU/ml) of TNF treatment. CONCLUSIONS: Patients with solid cancer and mild anaemia are characterised by inappropriate low plasma EPO concentration. Therapy with TNFalpha exerts a suppressive effect on EPO secretion in these patients.     

Catecholamine concentrations in plasma and organs of the fetal guinea pig during normoxemia, hypoxemia, and asphyxia

To examine the responses of the sympatho-adrenal system to reduced oxygen supply we studied plasma and tissue concentrations of catecholamines during normoxemia, hypoxemia, and asphyxia in 22 fetal guinea pigs near term. Fetal blood was obtained by cardiopuncture in utero under ketamine/xylazine-anesthesia. Catecholamines were determined in plasma and tissue of 15 organs and 14 brain parts by HPLC-ECD. During normoxemia (SO2 54 +/- 4 (SE) %, pH 7.36 +/- 0.02, n = 5) plasma catecholamine levels were low (norepinephrine 447 +/- 53, epinephrine 42 +/- 12, dopamine 44 +/- 6 pg/ml). During hypoxemia (SO2 27 +/- 3%, pH 7.32 +/- 0.01, n = 6) and asphyxia (SO2 24 +/- 2%, pH 7.23 +/- 0.02, n = 11) tissue catecholamine concentrations changed with changing blood gases and with increasing plasma catecholamines. Norepinephrine concentrations increased in both skin and lung and decreased in liver, pancreas, and scalp; those of epinephrine increased in the heart, lung liver, and scalp and decreased in the adrenal. There were only minor changes in brain catecholamine concentrations except for a 50% reduction in dopamine in the caudate nucleus. Concentrations of dopamine catabolite 3,4-dihydroxyphenylacetic acid decreased in many brain parts, suggesting that cerebral catecholamine metabolism was affected by hypoxemia and asphyxia. We conclude that the sympatho-adrenal system of fetal guinea pigs near term is mature and that its stimulation by reduced fetal oxygen supply leads to changes in both plasma and tissue catecholamine concentrations.     

Increased leukotriene C4 in ethchlorvynol-induced acute lung injury in dogs

We investigated whether ethchlorvynol (ECV)-induced acute lung injury (ALI) is associated with an increase in leukotriene C4 (LTC4) production. In six pentobarbital sodium-anesthetized dogs, ECV (15 mg/kg iv) introduced into the pulmonary circulation resulted in a 164 +/- 31% increase in extravascular lung water 120 min after ECV administration. Concomitantly, the mean (+/- SE) concentration of LTC4 in arterial plasma measured by radioimmunoassay following 80% EtOH precipitation, XAD-7 extraction and high-pressure liquid chromatography purification was 5.0 +/- 1.3 pg/ml, unchanged from control (pre-ECV) values. In contrast, in pulmonary edema fluid 120 min post-ECV, the LTC4 concentration was 35.2 +/- 10.8 pg/ml, sevenfold greater than those values found in the arterial plasma (P less than 0.01). In six additional dogs, 120 min after unilateral ALI had been induced with ECV (9 mg/kg iv), LTC4 in the bronchoalveolar lavage (BAL) of the uninjured lung was 12.1 +/- 1.5 pg/ml, unchanged from pre-ECV values, whereas, LTC4 in the BAL of the injured lung increased from a control value of 10.2 +/- 1.6 to 24.2 +/- 3.5 pg/ml (P less than 0.01) 120 min after ECV administration. These results demonstrate that, in ECV-induced acute lung injury, LTC4 concentrations in pulmonary edema fluid are considerably greater than those found in arterial plasma in the case of bilateral acute lung injury and significantly greater in the BAL of the injured lung compared with the uninjured lung in the case of unilateral acute lung injury. The results are a necessary first step in support of the hypothesis that leukotrienes participate in the altered permeability of ECV-induced acute lung injury.     

Ontogeny of gastric acidity in the ovine fetus

Hypoacidity and hypergastrinaemia have been reported in the newborn human. However, little is known about in utero gastric acid secretion, and the relationship to fetal plasma gastrin levels. The longitudinal pattern of development of basal and stimulated gastric acid secretion in the non-anaesthetized fetal sheep has been studied during the last 45 days of gestation. Fetuses had cannulae inserted into the jugular vein, carotid artery and stomach. Gastric juice and blood was sampled daily from 101 days gestation until birth (145 days). Intermittent basal acid secretion began between 120 and 133 days of gestation. These fluctuations in gastric juice pH continued until birth. Overall there was a decline in gastric pH from 7.5 +/- 0.2 (SEM), for fetuses 101-105 days to 4.3 +/- 0.5 by 131-135 days. Mean fetal plasma gastrin was higher than maternal levels after 111-115 days but no correlation between fetal plasma gastrin levels and gastric pH could be demonstrated. Pentagastrin and histamine infusion did not stimulate acid secretion in fetuses younger than 115 days. After this age the fetuses became responsive to both pentagastrin and histamine. In contrast, cholinergic stimulation, using bethanechol, did not stimulate acid production until 10 to 15 days later, suggesting a hierarchy in the development of the control of acid secretion in the fetus. The lack of response to endogenous gastrin and the hierarchy in the control of acid secretion suggest either a lack of receptors on the parietal cell or the presence of an inhibitor of acid secretion. These studies are relevant to human physiology since the present findings show that the sheep and human have a similar gastrin/acid profile at birth.     

The responses of the catecholamines and beta-endorphin to brief maximal exercise in man

The responses to brief maximal exercise of 10 male subjects have been studied. During 30 s of exercise on a non-motorized treadmill, the mean power output (mean +/- SD) was 424.8 +/- 41.9 W, peak power 653.3 +/- 103.0 W and the distance covered was 167.3 +/- 9.7 m. In response to the exercise blood lactate concentrations increased from 0.60 +/- 0.26 to 13.46 +/- 1.71 mmol.l-1 (p less than 0.001) and blood glucose concentrations from 4.25 +/- 0.45 to 5.59 +/- 0.67 mmol.l-1 (p less than 0.001). The severe nature of the exercise is indicated by the fall in blood pH from 7.38 +/- 0.02 to 7.16 +/- 0.07 (p less than 0.001) and the estimated decrease in plasma volume of 11.5 +/- 3.4% (p less than 0.001). The plasma catecholamine concentrations increased from 2.2 +/- 0.6 to 13.4 +/- 6.4 nmol.l-1 (p less than 0.001) and 0.2 +/- 0.2 to 1.4 +/- 0.6 nmol.l-1 (p less than 0.001) for noradrenaline (NA) and adrenaline (AD) respectively. The plasma concentration of the opioid beta-endorphin increased in response to the exercise from less than 5.0 to 10.2 +/- 3.9 p mol.l-1. The post-exercise AD concentrations correlated with those for lactate as well as with changes in pH and the decrease in plasma volume. Post-exercise beta-endorphin levels correlated with the peak speed attained during the sprint and the subjects peak power to weight ratio. These results suggest that the increases in plasma adrenaline are related to those factors that reflect the stress of the exercise and the contribution of anaerobic metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glucose and lactate turnover and gluconeogenesis in chronic metabolic acidosis and alkalosis in normal and diabetic dogs

The turnover rate of glucose, the irreversible disposal rate of lactate, and the rate of gluconeogenesis from lactate were calculated by tracer methods in four normal and four alloxan-diabetic dogs under control conditions as well as in chronic, stable metabolic acidosis and alkalosis. Acidosis was produced by feeding dogs 0.8-1 g.kg-1.day-1NH4Cl over 1 week, alkalosis was produced by feeding dogs a chloride-free diet and injections of furosemide. Mean plasma pH in the three states were 7.28 +/- 0.013, 7.40 +/- 0.024, and 7.51 +/- 0.015 in normal dogs, and 7.22 +/- 0.025, 7.42 +/- 0.009, and 7.49 +/- 0.002 in the diabetic dogs. Respective mean plasma bicarbonate levels were 14.6 +/- 0.88, 22.0 +/- 0.80, and 32.4 +/- 1.88 mequiv. in normal dogs, and 12.3 +/- 1.30, 22.6 +/- 0.66, and 35.0 +/- 1.14 mequiv. in diabetic animals. In normal dogs shifts in acid-base balance had no effect on the level of plasma glucose or the turnover rate of glucose. In diabetic dogs plasma glucose level was significantly elevated by alkalosis. Plasma lactate was positively correlated with plasma pH (r = 0.69, p less than 0.01) and was in general higher in diabetic than in normal animals. The increment in concentration was due to a decreased clearance of lactate from the plasma. The irreversible disposal rate was not changed by the acid-base status. Whereas a larger fraction of lactate removed from the plasma appeared in glucose in diabetic animals, this fraction was not changed significantly by shifts in the acid-base status.(ABSTRACT TRUNCATED AT 250 WORDS)     

Quantitation of the active and low-active forms of human plasma phospholipid transfer protein by ELISA

Human plasma contains two forms of phospholipid transfer protein (PLTP), one catalytically active [high-activity PLTP (HA-PLTP)] and the other a low-activity (LA-PLTP) form. We present here a PLTP ELISA that allows not only for accurate measurement of PLTP concentration in plasma but also of the distribution of both LA- and HA-PLTP. To achieve similar immunoreactivity of the two PLTP forms, a denaturing sample pretreatment with 0.5% SDS was required. Distribution of LA- and HA-PLTP in plasma was assessed using size-exclusion chromatography, Heparin-Sepharose chromatography, anti-PLTP immunoaffinity chromatography, and dextran sulfate-CaCl2 precipitation. All four methods demonstrated that approximately 60% of plasma PLTP represents LA-PLTP and 40% represents HA-PLTP. According to the modified ELISA, the total serum PLTP concentration in a random Finnish population sample (n = 80) was 5.81 +/- 1.33 mg/l (mean +/- SD) (range, 2.78-10.06 mg/l) and the mean activity was 5.84 +/- 1.39 micromol/ml/h (range, 3.21-11.15 micromol/ml/h). To quantitate both forms of PLTP in sera from this sample, we combined dextran sulfate-CaCl2 precipitation with the modified PLTP ELISA. The HA-PLTP mass (mean, 1.87 +/- 0.85 mg/l) correlated significantly with serum PLTP activity, whereas that of LA-PLTP (mean, 3.94 +/- 1.4 mg/l) showed no correlation with phospholipid transfer activity.     

Effect of selenium deficiency on the disposition of plasma glutathione

Selenium deficiency causes increased hepatic synthesis and release of GSH into the blood. The purpose of this study was to examine the effect of selenium deficiency on the disposition of plasma glutathione. Plasma glutathione concentration was 40 +/- 3.4 nmol GSH equivalents/ml in selenium-deficient rats and 17 +/- 5.4 nmol GSH equivalents/ml in control rats. The half-life and systemic clearance of plasma glutathione were found to be the same in selenium-deficient and control rats (t1/2 = 3.4 +/- 0.7 min). Because selenium-deficient plasma glutathione concentration was twice that of control, the determination that selenium deficiency did not affect glutathione plasma systemic clearance indicated that the flux of glutathione through the plasma was doubled by selenium deficiency. It has been proposed that the kidney is responsible for the removal of a major fraction of plasma glutathione. In these studies, renal clearance accounted for 24% of plasma systemic glutathione clearance in controls and 44% in selenium-deficient rats. This indicates that a significant amount of glutathione is metabolized at extrarenal sites, especially in control animals. More than half of the increased plasma glutathione produced in selenium deficiency was removed by the kidney. Thus, selenium deficiency results in a doubling of cysteine transport in the form of glutathione from the liver to the periphery as well as a doubling of plasma glutathione concentration.     

A simple and sensitive assay for determining plasma tipranavir concentration in the clinical setting by new HPLC method

A simple method for the quantification of tipranavir, the first non-peptidic HIV protease inhibitor, was developed and validated. Quinoxaline, as internal standard, was added to 50 microl of plasma before a liquid-liquid extraction by 600 microl of protein precipitation solution. The extracts were diluted before being injected in the chromatographic system. Chromatographic separation was made on a C18 column using potassium phosphate buffer (pH 3.2) and acetonitrile with gradient. Detection was performed by an UV detector at 260 nm. Relative error at three control quality concentrations ranged from -1.81 to 1.72%. Intra-day (CV%) and inter-day (CV%) precision ranged from 0.94 to 2.55% and from 3.07 to 4.24%, respectively. LOQ and LOD were 0.090 microg/ml and 0.035 microg/ml, respectively. Mean recovery was 87.1%+/-2.4%. Calibration curve was linear up to 180 microg/ml. Concentration range when optimized (0.703-180 microg/ml) proved to be adequate to measure tipranavir concentration in HIV-1-positive patients, therefore this method could be suitable for therapeutic drug monitoring of this drug.     

Blood-brain barrier to hydrogen ion during acute metabolic acidosis in piglets

The present study investigates the integrity of the blood-brain barrier to H+ or HCO3- during acute plasma acidosis in 35 newborn piglets anesthetized with pentobarbital sodium. Cerebrospinal fluid acid-base balance, cerebral blood flow (CBF), and cerebral oxygenation were measured after infusion of HCl (0.6 N, 0.191-0.388 ml/min) for a period of 1 h at a constant arterial PCO2 of 35-40 Torr. HCl infusion resulted in decreased arterial pH from 7.38 +/- 0.01 to 7.00 +/- 0.02 (P less than 0.01). CBF measured by the tracer microsphere technique was decreased by 12% from 69 +/- 6 to 61 +/- 4 ml.min-1.100 g-1 (P less than 0.05). Infusion of 0.6 N NaCl as a hypertonic control had no effect on CBF. Cerebral metabolic rate for O2 and O2 extraction was not significantly changed from control (3.83 +/- 0.20 ml.min-1.100 g-1 and 5.7 +/- 0.6 ml/100 ml, respectively) during acid infusion. Cerebral venous PO2 was increased from 41.6 +/- 2.1 to 53.8 +/- 4.0 Torr by HCl infusion (P less than 0.02) associated with a shift in O2-hemoglobin affinity of blood in vivo from 38 +/- 2 to 50 +/- 1 Torr. Cisternal cerebrospinal fluid pH decreased from 7.336 +/- 0.014 to 7.226 +/- 0.027 (P less than 0.005), but cerebrospinal fluid HCO3- concentration was not changed from control (25.4 +/- 1.0 meq/l). These data suggest that there is a functional blood-brain barrier in newborn piglets, that is relatively impermeable to HCO3- or H+ and maintains cerebral perivascular pH constant in the face of acute severe arterial acidosis. (ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma prolactin concentration increases after hypercapnia acidosis.

Responses of plasma prolactin (PRL) concentration to alterations in carbon dioxide pressure ( pCO(2)) induced by 4 min of rebreathing out of a bag with 6 l gas initially containing a concentration of 93% O(2) and 7% CO(2) (hypercapnia hyperoxia; HH) and 4 min of voluntary hyperventilation (VH) at a respiratory rate of 28 - 32 per minute were investigated in ten males. During rebreathing in HH, an augmentation of pCO(2) from 40.2 +/- 2.1 to 63.7 +/- 5.4 mmHg and a decrease of pH from 7.4 +/- 0.02 to 7.32 +/- 0.04 were found in capillary blood (p < 0.01). Neither breathing frequency (BF) nor plasma PRL changed during this period. After two minutes of post-rebreathing, pCO(2) and pH returned to basal values. BF increased from 2 min of rebreathing (12.4 +/- 1.9 breath/min) until 11 min of recovery period (18.1 +/- 4.9 breath/min) (p < 0.01), while plasma PRL increased from end of rebreathing (11.59 +/- 1.49 ng/dl) to 11 min of recovery period (13.63 +/- 1.97 ng/dl) (p < 0.01). In VH, hyperventilation decreased pCO (2) from 39.91 +/- 2.62 to 21.73 +/- 2.59 mmHg (p < 0.01) and increased pH from 7.39 +/- 0.04 to 7.58 +/- 0.04 (p < 0.01) in capillary blood. After four minutes of recovery from hyperventilation, pH and pCO(2) were back to their basal values. No changes in plasma PRL were found throughout VH. This present pilot study's new finding is that plasma PRL increases after hypercapnia acidosis. This indicates that acidosis-induced central chemoreflex function increases phrenic nerve activity based on serotonergic modulation, leading to an augmentation of BF. As serotonin is also the main PRL-releasing factor, this might have had the collateral effect of causing PRL release and delayed appearance in the peripheral circulation.     

Presence of a Ca2+-sensitive CDPdiglyceride-inositol transferase in canine cardiac sarcoplasmic reticulum

Sarcoplasmic reticulum (SR) and plasma membranes from canine left ventricle were used to evaluate the presence of the enzyme CDPdiglyceride-inositol transferase in these membranes. (K+,-Ca2+)-ATPase activity, a marker for SR, was 79.2 +/- 5.0 (SE) and 11.2 +/- 2.0 mumol.mg-1.h-1 in SR and plasma membrane preparations, respectively, and (Na+,K+)-ATPase activity, a marker for plasma membranes, was 5.6 +/- 1.2 and 99.2 +/- 8.0 mumol.mg-1.h-1, respectively. Contamination of SR and plasma membrane preparations by mitochondria was estimated to be 2% and 8%, respectively, and by Golgi membranes, 0.9% and 1.8%, respectively. Transferase activity, measured at pH 6.8, was 1.32 +/- 0.04 (SE) and 0.28 +/- 0.04 nmol of [3H]phosphatidylinositol ([3H]PtdIns).mg-1.min-1 in three SR and plasma membrane preparations, respectively. The transferase activity detected in the plasma membrane preparation could be accounted for largely, but not entirely, by contaminating SR membranes. The pH optimum for the SR transferase activity was between 8.0 and 9.0; little or no activity was detectable at pH 6.3 and 5.5, the lowest pH tested. Ca2+ inhibited the enzyme, half-maximal inhibition occurring at about 10 microM Ca2+; removal of the Ca2+ by addition of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid restored activity. No loss of [3H]PtdIns could be detected when membranes were incubated in the presence or absence of Ca2+. The Ca2+ inhibition of the transferase was noncompetitive with respect to CDP-dipalmitin while that with respect to myo-inositol was slightly noncompetitive at low [Ca2+] and became uncompetitive at higher [Ca2+].(ABSTRACT TRUNCATED AT 250 WORDS)     

Normal somatomedin and somatomedin receptors in achondroplastic dwarfism

It has been proposed that the basic abnormality in achondroplasia may be a quantitative defect in endochondral new bone formation secondary to decreased synthesis of somatomedin (SM) or abnormal binding of SM to specific receptors. To test this hypothesis, we have measured plasma SM levels and SM receptors on circulating mononuclear cells obtained from 5 achondroplastic dwarfs and 5 age-matched controls. Plasma SM levels were 0.82 +/- 0.14 U/ml (mean +/- S.E.M.) for the achondroplastic dwarfs and 0.90 +/- 0.12 U/ml for the controls. The specific binding of 125I-SM to 50 x 10(6) mononuclear cells was 7.66 +/- 1.11% for the dwarf group and 7.66 +/- 1.16% for the controls. Achondroplastic and control cells possessed equal numbers of receptor sites and identical receptor affinity for SM. The data indicate that plasma SM levels and SM binding to circulating mononuclear cells are normal in achondroplastic dwarfs and suggest a primary intrace-lular defect.     

Plasma atrial natriuretic peptide during brief upright and supine exercise in humans

The factors associated with the exercise-induced increase in plasma atrial natriuretic peptide (ANP) have not been clearly established. Thus the purpose of the study was to further document the stimulus for the exercise-induced release of ANP and to examine the role of ANP in the control of hydromineral balance during exercise. Eight healthy male volunteers (25.1 +/- 4.5 yr) were submitted to a graded cycling exercise in both the upright and supine positions. Venous blood was sampled at rest and at the end of each 5-min work load at 40, 60, and 80% maximal oxygen uptake (Vo2max), at maximal exercise, and during recovery through an indwelling catheter for the determination of plasma vasopressin, aldosterone, catecholamines, plasma renin activity, and ANP concentrations. Results indicate a significant increase in ANP (pg/ml) from rest to maximal exercise in the upright position [rest, 21.9 +/- 10.2; 40%, 24.7 +/- 12.6; 60%, 32.4 +/- 17*; 80%, 47.8 +/- 27.7*; 100% Vo2max, 65.9 +/- 34.5* (*P less than or equal to 0.05)]. Supine concentrations were significantly higher than upright at 40 (37.9 +/- 15.2), 60 (54.0 +/- 18.8), and 80% Vo2max (68.9 +/- 16.6). Plasma ANP during maximal exercise was similar in both positions. Plasma vasopressin, aldosterone, renin activity, and catecholamines increased with increasing exercise intensity in both positions, although lower values were systematically observed in the supine position. The association of higher plasma ANP and blunted plasma vasopressin, plasma renin activity, and norepinephrine concentrations during supine exercise suggests that ANP may exert modulatory effects on the control of the hydromineral hormonal system during exercise.