Leucine and Glucose Turnover in Chronic Alcoholics During Early Abstinence and After an Ethanol Load

We studied leucine turnover using a primed infusion of [1-¹⁴C]- l -leucine and glucose turnover using a primed infusion of [6-³H]- d -glucose in five alcoholic patients without liver damage and five age-matched controls. Infusions were maintained for 6 hr, and at the end of the 3rd hour, a 0.8 g/kg iv ethanol load was administered in 20 min. Leucine flux, nonoxidative disposal and oxidation rates, and glucose rate of appearance were calculated during the 3rd and 6th hours of infusion. Ethanol disappearance rate and the percentage completely metabolized to CO₂ and H₂O in 3 hr were also calculated. Compared with controls, alcoholics had significantly higher basal leucine flux (55.6 ± 12 vs. 37.3 ± 9.3 μ m /m²/min) and nonoxidative disposal (48.7 ± 8.7 vs. 31.1 ± 7.5 μ m /m²/min). No differences were observed in basal glucose appearance rates in alcoholics and controls (397.6 ± 115.2 vs. 349.4 ± 120.6 μ m /m²/min). Compared with controls, alcoholics had a higher alcohol disappearance rate (2.72 ± 0.59 vs. 1.84 ± 0.43 m m /kg/min) and percentage of ethanol metabolized to CO₂ and H₂O in 3 hr (40.6 ± 10.2 vs. 22.9 ± 6.9%). After the ethanol load, both leucine turnover and glucose rate of appearance decreased significantly only in alcoholics. There was a positive correlation between the change in leucine flux and ethanol disappearance rate and percentage metabolized to CO₂ and H₂O in alcoholics.     

The Pasteur effect in human platelets: implications for storage and metabolic control

Summary. The Pasteur effect and the associated acidosis have long been considered a major cause of platelet death during storage. We have investigated this phenomenon using a defined platelet preparation and a system whereby the oxidative and glycolytic contributions to total ATP production can be measured over a range of oxygen concentrations from saturating (pO₂=158mmHg) to anoxic (pO₂=OmmHg). Platelets do not show a Pasteur effect until the pO₂ decreases to & 2'OmmHg, whereupon lactate production increases 1-5-fold. The Pasteur effect is therefore not a likely cause of platelet death during storage where pO₂ in a storage bag typically drops to no less than 50mmHg. The data also have implications for the role of oxygen diffusion in oxidative metabolism, and for the compensatory nature of the Pasteur effect. As platelets are relatively small cells, and the onset of the Pasteur effect occurs at a relatively low oxygen concentration, diffusion may limit the rate of oxygen consumption in most other (larger) cells. The Pasteur effect is only fully compensative if the P/O₂ ratio used for the calculations is lower than the conventional one. Since recent research strongly suggests that the conventional P/O₂ ratio is too high, examples of fully compensative Pasteur effects may be more common than the literature suggests.     

Acute Hemodynamic, Pituitary, and Adrenocortical Responses to Alcohol in Adult Female Sheep

Alcohol was infused intravenously Into chronically cannulated adult female sheep as a 40% solution (w/v) at doses of 0.5,1.0, 1.5, or 2.0 g/kg over 1 hr. Saline infusions, equal in volume to the highest dose, served as a control. Dose-dependent peak blood alcohol concentrations (BACs) were attained 60 min after the beginning of alcohol infusion for all doses (88.5 ± 3.7, 213.2 ± 11.0, 373.2 ± 14.3, and 494.1 ± 34.5 mg/dl ± SE, respectively). Plasma cortisol concentrations Increased in response to the 0.5 g/kg infusions (BACs less than 100 mg/dl), whereas both ACTH and cortisol concentrations increased in the 1.0 and 2.0 g/kg dose groups. Mean arterial pressure, heart rate, and Pao₂, increased, whereas Pao₂, decreased in response to the 1.5 and 2.0 g/kg infusions. Arterial pH declined in the highest dose group. Respiratory rate was lower in all groups receiving alcohol compared with that of the control group. Hematocrit did not change. We conclude that BACs in adult female below 100 mg/dl (levels easily achieved by social drinkers) result in activation of the hypothalamus-pituitaty-adrenal axis. At high BACs (>350 mg/dl), pituitary adrenal responses are accompanied by increase in heart rate, blood pressure, and Pao₂, and decreases in Pao₂, and arterial pH. These findings support the hypothesis that alcohol acts directly on the brain to mediate pituitary adrenal responses and that the additional responses to high BACs (the blood gas and hemodynamic responses), might be mediated by direct actions of alcohol on the brain, by cerebral Ischemia, or by alcohol-mediated suppression of vemtilatory drive and hypoxemia.     

Arterial Hypoxaemia in Acute Myocardial Infarction

Summary: Serial measurements of arterial pO₂, pCO₂ and pH were made in 99 patients admitted to a coronary care unit with acute myocardial ischaemia or infarction. Samples were taken whilst the patients breathed room air and air enriched with oxygen in a concentration of approximately 40% via nasal cannulae. The degree of arterial hypoxaemia on room air correlated well with the degree of left ventricular failure. The increase in arterial oxygen tension produced by oxygen enrichment of the inspired air was greater in those with mild than in those with severe left ventricular dysfunction. The return of the arterial oxygen tension to normal after myocardial infarction may be protracted, suggesting that prolonged oxygen administration is advisable in the more severely ill patients. Levels of arterial pCO₂ and pH were not found to be helpful in management.     

A Comparative Study of Platelets Stored in Polyvinyl Chloride Containers Plasticised with Butyryl Trihexyl Citrate or Triethylhexyl Trimellitate

Platelet concentrates (PCs), stored for 5 days in PL 2209, a new polyvinyl chloride (PVC) storage container plasticised with butyryl trihexyl citrate, were compared with those stored in PL 1240, a PVC platelet container plasticised with triethylhexyl trimellitate. In part 1 of the study, pooled platelet-rich plasma (PRP) was aliquoted into each type of pack and pH, pCO₂, pO₂, hypotonic shock response, aggregation responses, lactate, glucose and ATP concentrations, and lactate dehydrogenase and β-thromboglobulin release were compared at days 1, 3 and 5. In part 2, 12 volunteers gave a unit of blood on two separate occasions and PCs produced by the PRP method were stored in PL 2209 or PL 1240 for 5 days before autologous reinfusion of a ¹¹¹In-labelled sample. In vitro results demonstrated that PL 2209 was more gas permeable than PL 1240. In part 2 of the study, at day 5, pCO₂ was 3.13±0.62 versus 5.14±0.69 (p<0.001), whilst pO₂ was not significantly different for PL 2209 versus PL 1240, respectively. pH was better maintained in PL 2209 than in PL 1240 (7.38±0.13 vs. 7.24±0.10, respectively, p<0.01) after storage for 5 days. These results were confirmed by those from part 1. In vivo data were similar for PC stored in the two plastics with a multiple-hit recovey of 40.9±12.1% for PL 2209 and 37.4±11.3% for PL 1240, and a multiple-hit survival of 4.89±1.20 days and 5.28±2.06 days for PL 2209 and PL 1240, respectively. γ-Camera imaging of volunteers showed similar biodistribution of radiolabeled platelets stored in each container. These results demonstrate that PL 2209 is a suitable container for storage of PCs for 5 days.     

Acute effect of ethanol on metabolite concentrations of dog pancreas in vivo

Sections of dog pancreas were freeze-clamped before and 1 hr after oral administration of 1 g/kg of ethanol in anesthetized, respirated, 24-hr-fasted animals, and multiple metabolites were determined in the perchloric acid extract of the frozen tissue. In spite of the fact that the pancreas contained little or no alcohol dehydrogenase activity (<0.01 lU/g of tissue), significant metabolite changes did occur. Although arterial oxygenation was constant and adequate (pO₂= 100±7 mM Hg) there was a significant 1.7-fold rise in L-lactate and fall in the cytoplasmic free [NAD+]/[NADH] ratio from 719±87 to 453±88 after ethanol. Except for a tendency for L-malate and L-α-glycerolphosphate to parallel the rise in L-lactate, there was little consistent disturbance in the remainder of the glycolytic metabolites (glucose, glucose 6-phosphate, pyruvate, 2-ketoglutarate, citrate, 3-phosphoglycerate, etc.) or in high energy intermediates and related compounds (ATP, creatine phosphate, AOP, Pi, creatine). There was, however, an unexpected and significant fall in the levels of the major transaminating amino acids, L-glu-tamate, L-aspartate, and L-alanine. The results can be only partially explained by an influence of blood-borne metabolites and imply significant effects of ethanol on the metabolism of the pancreas in vivo not directly mediated through alcohol dehydrogenase. Evidence is presented suggesting that both L-alanine and L-aspartate aminotransferases are functioning near equilibrium in the pancreas in vivo.     

I(Ks) block by HMR 1556 lowers ventricular defibrillation threshold and reverses the repolarization shortening by isoproterenol without rate-dependence in rabbits

Introduction: The slow delayed rectifier K⁺ current (I_Ks) contributes little to ventricular repolarization at rest. It is unclear whether I_Ks plays a role during ventricular fibrillation (VF) or ventricular repolarization at rapid rates during β-adrenergic stimulation.
Methods and Results: In an in vivo rabbit model, we evaluated the effects of HMR 1556 (1 mg Kg⁻¹+ 1 mg kg ⁻¹ hr ⁻¹ i.v.), a selective I_Ks blocker, on monophasic action potential duration at 90% repolarization (MAPD₉₀), ventricular effective refractory period (VERP), and defibrillation threshold (DFT). In perfused rabbit hearts, the effects of HMR 1556 (10 and 100 nM) in the presence of isoproterenol (5 nM) on MAPD₉₀ and VERP were studied at cycle lengths (CLs) 200–500 msec. In vivo , HMR 1556 prolonged MAPD₉₀ by 6 ± 1 msec at CL 200 msec (P < 0.01, n = 6), lowered DFT from 558 ± 46 V to 417 ± 31 V (P < 0.01), and decreased the coefficient of variation in the VF inter-beat deflection intervals from 8.9 ± 0.6% to 6.5 ± 0.4% (P < 0.05) compared with control. In perfused rabbit hearts, isoproterenol shortened MAPD₉₀ by 5 ± 1 msec at CL 200 msec and 11 ± 4 msec at CL 500 msec (P < 0.05, n = 7). This shortening was reversed by HMR 1556 (P < 0.05), and both effects were rate-independent.
Conclusion: I_Ks block increases VF temporal organization and lowers DFT, and I_Ks that is activated following β-adrenergic stimulation contributes to ventricular repolarization without rate dependence.     

Effects of Alcohol on Experimental Atrial Fibrillation

The association of alcohol abuse, especially binge drinking, and atrial fibrillation, recently termed "holiday heart," has been recognized for some time. The effects of alcohol on atrial fibrillation, however, have not been studied. Accordingly, measurements of hemodynamics and duration of electrically induced atrial fibrillation were made in α-chloralose anesthetized dogs during the 30 min before and during a 30-min intravenous infusion of 1.7 g/kg of ethanol (25%, v/v), which produced an average infusion concentration of 254 ± 21 mg/dl. Average cardiac output, left ventricular (LV) peak dp/dt, and pulmonary artery mean pressure did not change, whereas LV systolic (116 ± 8 to 107 ± 9 mm Hg, p < 0.05) and aortic mean (95 ± 7 to 87 ± 9 mmHg, p < 0.05) pressures decreased. Heart rate and atrioventricular conduction in sinus rhythm, and atrial and ventricular activity in atrial fibrillation also did not change. Despite a decrease in arterial pH, duration of atrial fibrillation decreased (356 ± 143 to 93 ± 38 sec, p < 0.05). Moreover, at 15 min, when average ethanol concentration was 208 ± 20 mg/dl, and aortic mean pressure (95 ± 7 to 85 ± 8 mm Hg, p < 0.05), pulmonary artery mean pressure (16 ± 2 to 14 ± 2 mm Hg, p < 0.05), and LV peak dp/dt (1563 ± 143 to 1285 ± 167 mm Hg-sec⁻¹, p < 0.05) were reduced, duration of atrial fibrillation was less than control (356 ± 143 to 114 ± 56 sec, p < 0.05). Thus, at blood levels of ethanol in which the vasodilatory and myocardial depressant effects of ethanol are evident, alcohol has an antiatrial fibrillatory effect.     

Metabolic Studies on the Erythrocyte from Patients with Chronic Renal Disease on Haemodialysis

S ummary . It is confirmed that ATP levels are significantly increased in uraemic (1.90±0.06 mmole/l RBC) as compared to control RBCs (1.30 ± 0.03 mmole/l RBC) ( P 0.001). Studies were performed which suggest that this increase in ATP may be secondary to an increased ATP synthetic capacity in uraemic erythrocytes which is independent of extracorpuscular factors including phosphate: (I) When suspended in an artificial low phosphate (PO₄) medium (I mM), washed RBCs from uraemic subjects produced and utilized ATP more rapidly than did washed control RBCs. (2) During a 12 hr incubation period, the ATP concentration of washed uraemic RBCs suspended in a 10 mM PO₂ medium remained significantly greater than the ATP level of washed control RBCs suspended in a 10 mM PO₄ medium. (3) During a 6 hr period of haemodialysis when the serum PO₄ level fell sharply, the RBC-ATP failed to change. Pyruvic kinase activities were significantly increased in uraemic (7.02 ± 0.84 EU/g Hb) as compared to control RBCs (3.20 ± 0.17 EU/g Hb) (P0.001), suggesting the presence of young RBCs in uraemia. It is proposed that the increased ATP levels and intrinsic ATP synthetic capacity may be due to the presence of an erythrocyte population with a younger mean age in the uraemic population studied.     

Supplemental Oxygen During Endoscopic Variceal Ligation: Effects on Arterial Oxygenation and Cardiac Arrhythmia

Objectives: Endoscopic variceal ligalion may affect cardiopulmonary function. The aim of this study was to determine the effect of either nasal oxygen (2 L/min) or no oxygen on arterial oxygenation and cardiac arrhythmia during variceai ligation.
Methods: A prospective, endoscopy team-blinded, randomized, cross-over study (first session vs second session) was conducted in 30 cirrhotic patients undergoing variceal ligation. Oxygen saturation (SaO₂) and cardiac arrhythmia were assessed by a pulse oximeter. In this study, 15 patients received supplemental oxygen in the first sessions, and 15 received oxygen in the second sessions.
Results: Oxygen desaturation (nadir SaO₂ < 90%) occurred in 23% of patients breathing room air but was prevented hy oxygen ( p < 0.01), and the nadir SaO₂ was significantly lower in patients breathing room air than in those receiving oxygen (93.2 ± 0.7% vs 98.3 ± 0.3%, p < 0.01). During the procedure, premature ventricular contraction was more frequently observed in patients breathing room air than in those receiving oxygen (14.0 ± 3.2/h vs 5.4 ± 1.5/r, p < 0.05).
Conclusions: These data suggest that oxygen desaturation and cardiac arrhythmia are common in patients undergoing variceal ligation and that low flow nasal oxygen can alleviate these events. Supplemental oxygen is therefore advisable to avoid potential serious cardiopulmonary accidents in patients undergoing variceal ligalion.     

Recombinant human interleukin-3: pharmacokinetics after intravenous and subcutaneous bolus injection and effects on granulocyte kinetics

The pharmacokinetics of E. coli derived recombinant human interleukin-3 (rhIL-3) was studied following intravenous (i.v.) and subcutaneous (s.c.) bolus injection of rhIL-3. After i.v. bolus injection in eight patients, serum peak levels of 34.5-135.0 ng/ml were reached, followed by a rapid decline with a t _1/2 α of 17 ± 2 min and a t _1/2β of 59 ± 7 min. After s.c. bolus injection in five patients, the absorption was more prolonged with peak serum levels reached at 2.8 ± 0.4h. Elimination was also more protracted, and serum base-line levels were reached at 14-24 h.
The immediate effect of rhIL-3 on peripheral white blood cells was less pronounced and more variable than previously found for G- or GM-CSF. Following i.v. administration, neutrophils showed a moderate drop to median 64% of initial values (range 42-85%) at median 30 min after injection (range 15-60 min) at median 30 min after injection (range 15-60 min) followed by an increase at 24 h to 69-288% of initial values. Eosinophils dropped to a median nadir of 34% and then gradually increased to maximum values in the range 135-720% at 18-24h. The effect of rhIL-3 was further examined following i.v. injection of autologous ¹¹¹Indium-labelled granulocytes in six patients. In steady state, i.v. injection of rhIL-3 caused a moderate drop in ¹¹¹Indium activity of peripheral blood within 20 min without tendency to subsequent recovery. No change occurred in the activity over the lungs and liver. The activity over the spleen decreased moderately in two patients. These results are strikingly different from those previously obtained after i.v. injection of rhGM-CSF.     

In Vitro Alcohol Dehydrogenase-Mediated Acetaldehyde Production by Aerobic Bacteria Representing the Normal Colonic Flora in Man

Excessive ethanol consumption has been related with the development of liver cirrhosis, as well as with rapid intestinal transit time and diarrhea. Moreover, heavy drinking is associated with an increased incidence of cancer of the oropharynx, larynx, esophagus, and colorectum. Acetaldehyde of microbial origin has recently been suggested as a possible pathogenetic factor behind this alcohol-associated gastrointestinal morbidity. The present in vitro study was aimed to investigate alcohol dehydrogenase activity and acetaldehyde formation capacity of some major aerobic bacteria representing the normal colonic flora in man. Cytosolic alcohol dehydrogenase activity and cytosolic protein concentration were determined spectrophotometrically. Alcohol dehydrogenase activity was then calculated as nmoles of reduced substrate produced by milligrams of protein per minute. The ability of different bacteria to produce acetaldehyde was determined by incubating the intact bacterial suspension in closed vials containing ethanol (final concentration 22 mM)for 1 hr at 37°C. The acetaldehyde formed during the incubation was analyzed by headspace gas chromatography. Marked differences in the alcohol dehydrogenase activity and acetaldehyde forming capacity were found among the strains tested. The alcohol dehydrogenase activity varied from 606 ± 91 nmol/min/mg protein ( Escherichia coli IH 50546) to 1 ± 0.2 nmol/min/mg protein ( E. coli IH 50817), and acetaldehyde formation varied from 1,717 ± 2 nmol acetaldehyde/10⁹ colony-forming units ( Klebsiella oxytoca IH 35403) to 5 ± 2 nmol acetaldehyde/10⁹ colony-forming units ( Pseudomonas aeruginosa ATCC 27853). There was a statistically significant correlation ( r = 0.77; p < 0.001) between alcohol dehydrogenase activity and acetaldehyde production from ethanol, strongly suggesting the catalytic role of bacterial alcohol dehydrogenase in this reaction.     

The Phosphodiesterase III Inhibitor Olprinone Decreases Sensitivity of Rat Kupffer Cells to Endotoxin

Background: Sensitivity of Kupffer cells to endotoxin [lipopolysaccharide (LPS)] and overproduction of tumor necrosis factor-α (TNF-α) are critical for progression of alcoholic liver injury. Therefore, suppression of TNF-α should prove useful for treatment of alcoholic liver injury. However, a transient increase of intracellular calcium ([Ca²⁺]_i) is required for LPS-induced TNF-α production by the macrophage cell line. The phosphodiesterase III inhibitor olprinone has been shown to suppress [Ca²⁺]_i level in vascular smooth muscle cells. Accordingly, the purpose of this study was to determine whether olprinone could prevent sensitization of Kupffer cells to endotoxin.
Methods: Kupffer cells were isolated by collagenase digestion and differential centrifugation. LPS was added to Kupffer cells 24 hr after incubation with or without olprinone (0.1 μmol/liter). After addition of LPS (10 μg/ml) to culture media, [Ca²⁺]_i was measured using a fluorescent indicator, fura-2.
Results: LPS increased [Ca²⁺]_i of Kupffer cells in control rats from basal levels (28 ± 4 nmol/liter) to 280 ± 14 nmol/liter. This increase was blunted by olprinone (91 ± 8 nmol/liter). Similarly, olprinone diminished the LPS (1 μg/ml)-induced TNF-α production by Kupffer cells by 30% (2220 ± 116 vs. 1386 ± 199 pg/ml; p < 0.05).
Conclusions: These results indicate that olprinone decreases sensitivity of Kupffer cells to endotoxin.     

Alpha1-Adrenergic Receptor Modulation of Repolarization in Canine Purkinje Fibers

Alpha-Agonists and Repolarization. Introduction: Alpha-adrenergic receptor stimulation increases contractility and prolongs repolarization. These effects are modulated by α₁-adrenergic receptor-mediated inhibition of transsarcolemmal potassium currents.
Methods and Results: We used standard microelectrode techniques to study the actions of 4-aminopyridine (4-AP), which blocks the transient outward current, I_to, and WAY-123,398, which blocks the delayed rectifier, I_k, on canine Purkinje fiber action potential prolongation induced by phenylephrine. At a basic cycle length of 1 second, phenylephrine (0.1 to 10 μ) dose-dependently prolonged action potential duration at 90% repolarization (APD₉₀) from 331 ± 10 msec to 400 ± 12 msec (P < 0.05) at phenylephrine, 10 μ. Phenylephrine did not change phase 1 or plateau height. 4-AP (0.1 mM) decreased phase 1 magnitude, shifted plateau height to more positive potentials (from 0.1 ± 1.8 mV to 14.3 ± 1.1 mV [P < 0.05]), and shortened APD₉₀ from 318 ± 9 msec to 294 ± 8 msec (P < 0.05). 4-AP did not block phenylephrine effects on APD₉₀, which increased, at 10 μ phenylephrine, from 294 ± 8 msec to 342 ± 6 msec (P < 0.05). In contrast, WAY-123,398 (0.1 μ) prolonged APD₉₀ from 360 ± 6 msec to 452 ± 6 msec (P < 0.05), and had no effect on plateau height. In the presence of WAY-123,398, phenylephrine no longer increased APD_9o.
Conclusion: (1) Agents that block I_to shorten APD in Purkinje fibers; and (2) the α-agonist mediated increase of APD in canine Purkinje fibers can be explained by inhibition of I_k.     

Influence of a Methanogenic Flora on the Breath H2 and Symptom Response to Ingestion of Sorbitol or Oat Fiber

Background and Objectives: We investigated the possibility that a variant of the normal colonic flora, a high concentration of methanogeas, influences the host's response to ingestion of nonabsorbable, fermentable materials. Methods: To better evaluate symptomatic and breath H₂ and methane (CH₄) responses, subjects were placed on a basal diet (primarily rice and hamburger) that contained minimal amounts of nonabsorbable, fermentable substrate. A breath CH₄/H₂ ratio of greater or less than 1 on the second day of the basal diet was used to categorize subjects as high (N = 9) or low (N = 25) CH₄ producers. After stabilization of the breath gas excretion (day 3 or 4 on the basal diet), the subjects ingested either sorbitol (8.8 g) or oat fiber (10.2 g). Results: The low CH₄ producers had a signficantly higher ( p < 0.05) breath H₂ concentration than the high producers on the basal diet and after ingestion of sorbitol (27.1 ± 2.7 ppm vs 15.8 ± 3.6 ppm) or oat fiber (13.1 ± 0.08 ppm vs 9.6 ± 1.2 ppm). Low producers of methane reported significantly increased bloating and cramping after sorbitol ingestion and increased bloating after fiber ingestion, whereas high CH₄ producers reported no signficant increase in these symptoms. Conclusion: The presence of a methanogenic flora is associated with a reduced symptomatic response to ingestion of nonabsorbable, fermentable material in healthy subjects. Manipulation of the normal flora could be of therapeutic value in nonmethanogenic patients with irritable bowel syndrome.     

The transport of two iron chelators, desferrioxamine B and L1, across Caco-2 monolayers

Summary. The transport of two iron chelators, desferrioxamine B (DFO) and L1 (1,2-dimethyl-3 hydroxypyridin-4-one) has been studied in vitro using the human adenocarcinoma cell line, Caco-2. The transport of DFO and L1 has also been compared with that of their iron-bound complexes, ferrioxamine (FO) and L1₃-Fe, respectively. We report an apparent permeability coefficient (P_app) value for DFO of 0.170 × 10⁻⁷± 0.080 cm s⁻¹. The P_app value of L1 was 1.297 × 10⁻⁵± 0.133 cm s⁻¹. The P_app values of their iron bound complexes FO and L1₃-Fe are 0.230 × 10⁻⁷± 0.065 cm s⁻¹ and 2.356 × 10⁻⁶ 0.365 cm s⁻¹, respectively. We have shown that the transport of DFO and FO is similar in the Caco-2 cell system. The transport of L1, however, is greatly reduced when complexed to iron. The value for total uptake after 60 min for DFO into the Caco-2 cells was 1.49 ± 0.09 × 10⁻³ nmol per filter. The values for total uptake after 60 min for L1 and L1₃-Fe were 0.37 0.03 nmol per filter and 0.04 ± 0.01 nmol per filter, respectively. Our results indicate that the poor oral bioavailability of DFO can be attributed to the low epithelial permeability of the molecule coupled with its size (mol wt 656). In contrast, the oral bioavailability observed with L1 is due to the high lipophilicity and low molecular weight (mol wt 139) of the molecule. We believe that these differences between the two molecules account for L1 being better orally absorbed than DFO.     

Do HbSS erythrocytes lose KCl in physiological conditions?

KCl cotransporter activity in sickle (HbSS) red blood cells (RBCs) was measured in cells suspended in 'simple' physiological saline, saline augmented with inorganic salts, and autologous plasma. Our results showed that the transporter was only functioning at 20% of the level of cells in saline when cells were resuspended in autologous plasma. Kinetic analysis of the data showed that plasma decreased both V _max and K _m for K⁺ of the transporter. The plasma factor(s) responsible was heat-stable and dialysable (i.e. size &60; 10 kD).
Adding magnesium, calcium, inorganic phosphate or bicarbonate to 'simple' saline to mimic the effect of plasma revealed that Mg²⁺ and Ca²⁺ had no significant effect at physiological concentrations. P_i was not effective at 1.1 m M  , but did inhibit significantly (42±2%) at 5.6 m M  . HCO⁻₃   had a major inhibitory effect on K⁺ influx when added to saline, and was identified as the principal candidate for the plasma effect.
We suggest bicarbonate may play a significant role in modifying KCl cotransport, and hence HbSS cell volume in vivo . It acts by altering the set point of the transporter via the signalling systems involved in its regulation.     

Existence and function of opioid receptors on nammalian pinealocytes

Abstract: Previous studies in our laboratories have identified a single population of opioid receptors in bovine pineal gland, which we have chosen to characterize further on pinealocytes isolated from the cow and rat pineal gland. The bovine pinealocytes isolated by trypsinization or mechanical manipulation revealed receptor density (B_max) values of 206.95 ± 131.15 and 220.34 ± 11.80 fmol/mg protein, respectively, and dissociation equilibrium constant (K_d) values of 1.93 ± 0.48 and 1.96 ± 0.21 nM, respectively. The rat pinealocytes cultured for 7 days exhibited a [³H]diprenorphine binding site of 56 fmol/10⁶ cells. Morphine (100 μM) enhanced the activity of N-acetyltransferase and the level of melatonin in rat pineal gland in culture incubated for 21 hr. The results of these studies suggest that opioidergic receptors exist on pinealocytes and they are involved in stimulating the activity of N-acetyltransferase and the synthesis of melatonin, thereby regulating the physiology of mammalian pineal gland.     

Possibility of 5-HT3 Receptor Involvement in Alcohol Dependence: A Microdialysis Study of Nucleus Accumbens Dopamine and Serotonin Release in Rats with Chronic Alcohol Consumption

The present study was performed to examine the involvement of serotonin-3 (5-HT3) receptors in the rat nucleus accumbens (ACC) in alcohol dependence. In alcohol-treated rats, perfusion of 40 mM K⁺ and 100 mM ethanol (EtOH) through the microdialysis probe increased the extracellular levels of ACC dopamine (DA), compared with controls. Perfusion of the serotonin (5-HT) uptake inhibitor sertlarine enhanced the extracellular levels of ACC 5-HT in both groups. Increased 5-HT availability in the synaptic clefts on the ACC further activated ACC DA release in the alcohol-treated rats, in comparison with controls. In the final experiments, perfusion of the 5.0 μ M 5-HT₃ receptor agonist 2-methyl-5-HT (2-Me-5-HT) through the microdialysis probe enhanced the extracellular levels of ACC DA. Magnitude of 2-Me-5-HT-induced DA release was significantly higher in alcohol-treated rats than in controls. On the other hand, 40 mM K⁺- and 100 mM EtOH-induced extracellular 5-HT release in alcohol-treated rats were markedly inhibited. These results show that (1) chronic alcohol intake increases the sensitivity of 5-HT₃ receptors, (2) 5-HT₃ receptors regulate DA release in the ACC, (3) the dopaminergic neuronal systems associated with 5-HT₃ ionophore in the ACC were upregulated after chronic alcohol exposure, and (4) chronic alcohol intake desensitizes the serotonergic neuronal systems in rat ACC. These findings suggest that neurochemical functions of 5-HT₃ receptors in regulating DA release in the ACC after alcohol exposure compensate for the dysfunction of serotonergic activity to restore the original properties in processing alcohol tolerance and that the development of alcohol dependence may be mediated by ACC 5-HT₃ receptors.