Elimination of infused amino acids from plasma of control subjects and of patients with cirrhosis of the liver

Abstract. In four control subjects and four patients with cirrhosis of the liver a multiple amino acid mixture was infused for 12 h at a constant rate of 68 and 56 μmol α-amino N/s, respectively. Before infusion the plasma amino N concentration was 2·4 pL 0·2 (mean pL SD) mmol/l in control subjects and 3·5 pL 0·7 mmol/l in patients ( P 0·025). The concentration of alanine, proline, arginine, tyrosine, and citrulline was significantly increased in the cirrhosis group. 12 h after the infusion began approximately constant amino N concentrations of 11·4 pL 1·8 mmol/l in controls and 13·7 pL 3·9 mmol/l in patients were attained, and the urea N synthesis rate was 63 pL 17 and 44 pL 8 μmol/s, respectively ( P < 0·05). After correction for loss of amino acids in urine this means that on the average 94 per cent of the N load was recovered as urea. The plasma clearance of infused amino acids, calculated as the ratio between infusion rate and steady state concentration, was 6·0 pL 1·2 and 4·1 pL 0·9 ml/s for amino N in the control and cirrhosis group, respectively ( P < 0·025). The clearance of individual amino acids ranged between 2·5 and 28 ml/s. The clearance of most amino acids was decreased in the cirrhosis group, and of glycine, proline, lysine, threonine, and arginine significantly so ( P < 0·05), reflecting accumulation of amino acids in patients. This indicates that a primary defect in the conversion of amino N in cirrhosis is the reduced urea synthesis.     

Study of the pharmacokinetics of cefpirome sulphate in the elderly

Objective: To determine the appropriate method of administration of the cephem antibiotic cefpirome sulphate in elderly patients. Method: We studied cefpirome's pharmacokinetics in patients with urinary tract infections. Patients received cefpirome sulphate 0·5 g by intravenous drip infusion over 30 mins. Results: Patients with a creatinine clearance rate (Ccr) of 80 ml/min had an AUC of 96·7 μg·h/ml and a T _1/2 of 2·36 h, whereas those with Ccr of 40–80 ml/min had an AUC of 172·0 μg·h/ml and a T _1/2 of 3·45 h and those with Ccr of < 40 ml/min had an AUC of 152 μg·h/ml and a T _1/2 of 4·86 h. Conclusion: These results indicate that decreased kidney function can cause increases in the AUC and T _1/2 of cefpirome. Thus in elderly patients and perhaps also in other patients with decreased kidney function, cefpirome should be administered at an initial dose of 0·5 g.     

Erythrocyte uroporphyrinogen-I-synthase activity in β-thalassaemic patients

Abstract. The haem pathway enzyme uroporphyrino-gen-I-synthase (UPGS) was assayed in erythrocyte samples from twenty normal, twenty β-thalassaemia heterozygotic and twenty jS-thalassaemia homozygotic subjects, after partial separation of the erythrocytes according to their age. UPGS erythrocyte enzyme concentration activity was significantly higher in the young than in the old erythrocytes of normal (66·5 ± 11·8 v. 45 ± 9·5 nmol h^-1 I^-1, mean ± SD, P < 0·001) and β-thalassaemia heterozygotic subjects (70·1 ± 18·7 v. 49·8 ± 14·5 nmol h^-1 I^-1, P lt; 0·001), but not in patients with homozygous β-thalassaemia (46·0 ± 12·8 v. 44·1 ± 12·5 nmol h^-1 I^-1, P = 0·65). Furthermore, UPGS enzyme concentration of both young and old erythrocytes of homozygous β-thalassaemia was significantly lower than that of the young ( P < 0·001) but similar to that of the old ( P > 0·2) erythrocytes of either normal or β-thalassaemia heterozygotic subjects. Since severe chronic haemolysis due to haemoglobinopathies is associated with increased UPGS enzyme concentration, these results suggest that UPGS activity may be suppressed in homozygous β-thalassaemia.     

Glycaemic control and in vivo non-oxidative Maillard reaction: urinary excretion of pyrraline in diabetes patients

The presence of pyrraline in human urine has recently been described. Using reversed-phase high-performance liquid chromatography, we measured urinary pyrraline in 45 insulin-treated diabetic patients with preserved renal function and in 30 age- and sex-matched healthy subjects. The relationship between urinary pyrraline and metabolic control parameters in the diabetic population (glycaemia, fructosamine, haemoglobin Al_c, and 1-year mean haemoglobin A1_c) was evaluated. The mean urinary level of pyrraline in diabetic patients with poor glycaemic control (HbA_1c > 9.5%) was higher than that in healthy subjects (1.12 ± 0.35 vs. 0.75 ± 0.2 μmol mmol⁻¹ creatinine, P  < 0.04), whereas in patients with good to moderate glycaemic control (HbA1_c < 9.5) it was slightly but not significantly higher than in healthy subjects (0.80 ± 0.3 μmol mmol⁻¹ creatinine vs. 0.75 ± 0.2 μmol mmol⁻¹ creatinine). There is a significant correlation between urinary pyrraline level and glycaemia ( P  < 0.008), haemoglobin A1_c ( P  < 0.01) and 1-year mean haemoglobin A1_c values ( P  < 0.007), but not with fructosamine. The results of the present work prove, for the first time, that glycaemic status influences circulating levels of advanced Maillard reaction products.     

The individual variation in pharmacokinetics and pharmacodynamics of furosemide in young normal male subjects

Abstract. Following a 24 h control period in the ward 80 mg furosemide was injected intravenously to ten young healthy, male volunteers. The serum clearance of furosemide (Cl_s) was between 140 and 201 ml min^-1 and on the average the renal clearance was 66% of Cl_s. During the initial 30 min period a maximum additional excretion rate of sodium of 3·3 mmol min^-1 was reached at an excretion rate of 0·8 mg furosemide min^-1. A marked initial drop in creatinine clearance (Cl_cr) was noted and Cl_{cr(24 h)} showed an average decrease of 12% after the drug administration. The serum concentration of potassium was decreased at 1 and 2 h after the injection and of sodium from 2 h and on. The concentration of albumin in serum increased by 3% ( P < 0·05) already after 5 min. After 2 h a maximum increase of 14% was reached. After 8 min diastolic blood pressure was increased by 13% ( P < 0·05), whereas systolic blood pressure reached a significant decrease gradually (7% after 3 h).     

Serum β2-microglobulin at remission and relapse in patients with multiple myeloma

Abstract. Serum β₂-microglobulin (S-β₂m) was determined before treatment in fifty patients with multiple myeloma (MM), twenty-two of which had pure Bence Jones (BJ) myeloma. S-β₂m was related to clinical stage before, but not after, a correction of S-β₂m values for co-existent raised S-creatinine values (> 106 μmol 1^-1)- However, S-β₂m as well as corrected β₂m was a parameter of prognostic value. The median expected survival time was 14 months at S-β₂m values > 8·0 mg 1^-1 and 56 months at values<3·5 mg 1^-1. A response to treatment was associated with a decrease of S-β₂m and a stationary course with unchanged values, whereas a relapse or progressive disease was connected with an increase. In β₂m producers', i.e. patients with a clear initial high S-β₂m, serial determinations are of value for monitoring patients with MM. In particular, this is the case in BJ myelomas, as they lack a quantifiable serum M-component. With respect to β₂m no difference was found between BJ and other patients with MM.     

Kidney function and size in normal subjects before and during growth hormone administration for one week

Abstract. Kidney function and size were studied in seven normal male subjects before and after administration of highly purified human growth hormone for 1 week. Glomerular filtration rate, renal plasma flow (steady-state infusion technique with urinary collections using ¹²⁵I-iothalamate and ¹³¹I-hippuran) kidney size (ultrasonic scanning) and urinary excretion rates of albumin and β₂-microglobulin (radioimmunoas-says) were measured. Highly purified growth hormone was injected subcutaneously, 2 IU in the morning and 4 IU in the evening. Glomerular filtration rate increased from (mean ± SEM) 114 ± 5 to 125±4ml/min x 1.73 m² ( P <0.01) and renal plasma flow increased from 554 ±30 to 601 ±36 ml/min ×1.73 m²( P < 0.01). Kidney size and urinary excretion rates of albumin and β₂-microglobulin did not change significantly.
Our results show that raising plasma growth hormone into a range similar to that found in insulin-dependent diabetics enhances glomerular filtration rate and renal plasma flow, while kidney size remains unchanged. Increased renal plasma flow is the major determinant of growth hormone induced elevation in glomerular filtration rate. Growth hormone may thus contribute to the enhancement of glomerular filtration rate and renal plasma flow typically found in insulin-dependent diabetics.     

Pharmacokinetics and influence of arbekacin on renal function in low-birth-weight infants

Arbekacin (ABK) is an aminoglycoside with excellent antibacterial activity against methicillin-resistantStaphylococcus aureus (MRSA). Although ABK is expected to be a useful drug for MRSA infection in newborns, there have been few reports concerning its pharmacokinetics, efficacy, and safety. Ten low-birth-weight infants were treated with ABK. Their mean gestational age was 29.4±5.3 weeks and their mean birth weight was 1204±532 grams. At the time of initial ABK administration, the mean postconceptional age was 33.9±4.2 weeks. ABK was infused over a period of 30 minutes every 12 hours at doses ranging between 2.2 and 3.1 mg/kg. Trough (predose) and peak (30 minute postdose) serum ABK concentrations were determined. TheN-acetyl-β-d-glucosaminidase (NAG) index (NAG:creatinine ratio) was measured before and after ABK therapy. The mean peak serum ABK concentration was 8.49±2.06 μg/mL and the mean trough concentration was 3.93±2.14 μg/mL, with a mean half-life of 11.4±6.1 hours. A significant negative correlation existed between postconceptional age and ABK half-life (r=0.64;P<0.05), and there was a positive correlation between postconceptional age and ABK clearance (r=0.83;P<0.05). The NAC index significantly increased after ABK therapy (P<0.05), and a significant positive correlation was found between the though level of ABK and the NAG index after ABK therapy (r=0.84;P<0.05). ABK, similar to other aminoglyoosides, should be used with caution in low-birth-weight infants with careful attention given to their renal function.     

Distal renal tubular dysfunction: a common feature in calcium stone formers

Abstract. Distal renal tubular acidosis has been reported as an uncommon cause of urinary calcium stone disease. However, this defect appears to be more frequent when appropriate tests are performed systematically. Twenty-nine patients with recurrent calcium stones have been separated into three groups: normocalciuric (group A), renal hypercalciuric (group B) and absorptive hypercalciuric (group C). Distal tubular functions were investigated by the (urine-blood) pCO₂ gradient and by an ammonium chloride test. (Urine–blood) pCO₂ gradient was (mean pL SEM), 3·33 pL 0·59 in group A, 2·95 pL 0·34 in group B and 3·31 pL 0·58 kPa in group C. All these values differ significantly from those observed in controls (4·11 pL 0·28 kPa; P < 0·05). After 3 days of ammonium chloride loading, ammonium excretion averaged 54·7 pL 4·2 in group A, 54·4 pL 4·3 in group B and 64·3 pL 5·5 μmol min^-1 in group C. Values obtained in the first two groups were significantly lower than that achieved by control subjects (76·4 pL 14·9 μmol min^-1). It is concluded that tubular dysfunctions defined as impairments in hydrogen ion secretion and ammonium excretion after an acid challenge are a common feature of the urinary calcium stone disease and play a contributory role in its pathogenesis.     

Erythropoietic activity and iron metabolism in autologous blood donors during recombinant human erythropoietin therapy

Abstract. The use of recombinant human erythropoietin (rhEPO) to intensify the erythropoietic response in autologous donors may reduce homologous blood requirement. We studied the effect of subcutaneous rhEPO (500 U kg^-1 body weight twice weekly during a 3 week period) on variables of erythropoiesis and iron metabolism in 62 autologous blood donors, of whom 32 received rhEPO (epo group) and 30 did not (control group). Patients donated only 2 units of blood and received oral iron in order to restrict phlebotomyinduced decrease of iron stores. Pre-phlebotomy haemoglobin concentration (14·0±0·8 g dl^-1) was completely regenerated in the epo group at surgery (13·7±1·3 g dl^-1); haemoglobin concentration in the control group fell from 13·5±1·4 g dl^-1 to 11·6±1·4 g dl^-1 after the phlebotomies and did not improve during the pre-operative phase. Total erythropoietic activity expressed as serum transferrin receptor concentration (sTfR) showed a 4-fold increase from 3·8±0·9 μ g ml^-1 to 14·9±4·8 μ g ml^-1 in the epo group. Effective erythropoietic activity measured by absolute reticulocyte count, however, declined after the fourth rhEPO injection in the epo group. Serum ferritin was lower in the epo group, but no differences in serum iron, transferrin concentration and transferrin saturation were observed between the groups. A marked increase in free erythrocyte protoporphyrin (FEP) was observed in the epo group, whereas FEP levels in the controls remained within normal ranges. Despite oral iron supplementation and the limited number of phlebotomies, the effect of rhEPO therapy in autologous donors is restricted by iron depletion.     

Methodological limitations of the use of intrinsic hepatic clearance of ICG as a measure of liver cell function

Abstract Negligible extra-hepatic elimination of indocyanine green (ICG) makes it well suited as a liver test substance. The liver blood flow rate ( Q ) is estimated from concentration measurements in peripheral ( A ) and hepatic venous ( V ) blood during a constant ICG infusion rate (Inf), as Q = Inf/( A – V ). Intrinsic hepatic clearance of ICG, Cli = Inf/((A – V)/In( A/V )), is interesting because it should give a flow-independent quantitative estimate of liver cell function, utilizing the same concentration measurements. The present study was aimed to investigate possible limitations involved in the estimation and use of Cli of ICG in 41 liver patients and 20 controls. Time-dependence was studied by means of two successive 40-min infusion periods (with no significant change in Q ). Cli of ICG decreased 6% per hour ± 3% (mean ± SD, n = 6, P < 0·01) due to a small but significant increase of the concentrations during the infusion period. Flow-dependence was studied by measurements before and after an increment of flow of on average 51%, induced by the intake of a meal. This caused no significant change in Cli of ICG ( P > 0·5, n = 5, Student's paired t -test). The intrinsic hepatic clearance of ICG was on average 0·75 ± 0·26 1 plasma min^-1 (± SD, n = 20) in controls and 0·39 ± 0·18 1 plasma min^-1 in liver patients ( n = 41), P < 0·001. It was positively correlated to the galactose elimination capacity, although the scatter was large ( P < 0·05, n = 56). This might be due to the fact that Cli depends both on liver cell function and on intra-hepatic vascular shunting of blood.     

The in vivo effect of interleukin-1β on urea synthesis is mediated by glucocorticoids in rats

Abstract. Interleukin-1 β has been proposed as one mediator of parts of the catabolic response following surgery. However, it is not known whether such an effect is due to interleukin-1 β itself or the associated changes in glucocorticoids.
The effect of interleukin-1 β on urea synthesis was investigated in rats given a high (10 μg kg^-1) and a low dose (0·1 μg kg^-1) of recombinant interleukin-1 β (NOVO, Denmark) 3 h prior to determination of the rate of urea synthesis in vivo . Urea synthesis increased dose-dependently after the low dose from 4·0±0·3 (control) to 6·3±0·3 ( P <0·01), and after the high dose to 7·7±0·3 μmol (min·100 gBW)^-1 ( P <0·01). The blood concentration of amino acids fell during interleukin-1 β treatment, so the effect on urea synthesis was not due solely to increased proteolysis, but was exerted predominantly in the liver.
Pharmacological glucocorticoid receptor blockade (hormone analogue RU486, Roussel–Uclaf, Paris, France) given 1 h prior to the interleukin treatment, completely abolished the interleukin-1 β induced increases in urea synthesis. The study demonstrates that interleukin-1 β stimulates urea synthesis in vivo , and that the major part of the effect depends on glucocorticoid action.     

Population pharmacokinetics of amikacin in intensive care unit patients studied by NPEM algorithm

Summary— The population pharmacokinetics of amikacin was studied in 40 intensive care unit patients (212 plasma concentrations) by NPEM algorithm using a one-compartment model. The population was best characterized by the following pharmacokinetic parameters: renal clearance relative to creatinine clearance (C_s = 0.96 ± 0.33), and either the total volume of distribution (V_d = 23.9 ± 7.0 I) or the volume of distribution relative to body weight (V_s = 0.36 ± 0.10 1·kg⁻¹. The volume of distribution was increased with respect to the usual value of 0.25 1·kg⁻¹. The statistical distribution of these pharmacokinetic parameters was approximately gaussian, with no significant correlation between volume of distribution and clearance. The medians and standard deviations of C_s and V_s were used as reference population values to estimate the pharmacokinetics of amikacin in a second group of 29 patients by the bayesian method, with two blood samples per patient. For each patient, the fitted parameters were able to predict the plasma concentrations of amikacin during the next 72 h with no significant bias and good precision (2.9 mg·1⁻¹ for peaks and 0.5 mg·1⁻¹ for troughs). This study confirms the ability of the NPEM algorithm to provide reference population values for use in bayesian monitoring of aminoglycoside therapy.     

Lack of correlation between endotoxaemia and renal hypoperfusion in cirrhotics without overt renal failure

Abstract. Renal involvement in patients with liver cirrhosis is characterized by renal vasoconstriction, the aetiology of which remains obscure. Endotoxaemia, frequently found in patients with liver cirrhosis and renal failure, has been emphasized as a pathogenic factor.
In fifty-seven patients with liver cirrhosis without overt renal failure endotoxin plasma level (Limulus Lysate test), mean renal blood flow (MRBF) (¹³³Xe washout technique), and effective renal plasma flow (ERPF) (p-aminohippurate clearance) were determined.
MRBF was decreased in nineteen out of twenty-seven patients, averaging 1·88 ± 0·51 ml g^-1min^-1 (in fourteen controls 3·17 ± 0·51 ml g^-1ml^-1). ERPF was decreased in seventeen out of thirty patients, averaging 380±164 ml/min (in eighteen controls 624±127 ml/min). Systemic endotoxaemia was found in sixteen out of fifty-seven patients, levels ranging from 0·62 to 200 ng/ml. No significant difference in renal blood flow values was found between patients with and without endotoxaemia (MRBF = 1·78 ± 0·51 and 1·93 ± 0·52 ml g^-1min^-1 respectively; ERPF = 429±119 and 365±175 ml/min respectively). No significant difference in the frequency of endotoxaemia was found between patients with impaired and unimpaired renal blood flow. Moreover no relation was found between endotoxin plasma levels and MRBF and ERPF respectively.
In conclusion in patients with cirrhosis without overt renal failure renal vasoconstriction does not seem to be related to endotoxaemia.     

The pharmacokinetics of porcine glucose-dependent insulinotropic polypeptide (GIP) in man

Abstract. The pharmacokinetics of porcine glucose-dependent insulinotropic polypeptide were investigated in six healthy volunteers. At the maximum infusion dose (0·5 pmol kg^-1 min^-1) a plateau concentration of 115 ± 5·0 pmol/l plasma was obtained. On discontinuation of the infusion, the half-time of disappearance was calculated to be 20·3 ± 1·2 min. The metabolic clearance rate was 2·6 ± 0·1 ml kg^-1 min^-1 and the apparent space of distribution was 75·8 ± 5·7 ml kg^-1. Blood glucose, pancreatic and gastrointestinal hormones remained at basal concentrations throughout. No side effects were noted by any of the subjects studied.     

Kinetics of circulating hyaluronan in humans

Abstract The elimination of intravenously injected hyaluronan (HA) from the blood was investigated in 12 healthy volunteers. Three consecutive 30 min infusions of HA were given, separated by 90 min washout periods. Blood samples were taken before, during and after each infusion and the plasma HA concentration was determined. The deposition of HA was modelled according to a Michaelis–Menten kinetic model which included natural synthesis of HA. K_m and V_max was estimated to 0·34 ± 0·13 μgml^-1 and 3·48 ± 0·97/μmin^-1kg^-1 b.w., respectively. The endogenous input was calculated to be 24 ± 11 μg min^-1 and was found to correlate to the age of the subjects ( P < 0·05). As the baseline HA concentration was 0·031 ± 0·21 μg ml^-1, the rate of elimination was linear in the normal concentration range. The calculated V_d was about 75% higher than a weight-estimated plasma volume. The total amount of HA excreted by the kidneys during the study period was 394 ± 77 μg, which corresponded to approximately 1·7% of the total input of HA into the circulation during the experiment.     

Pharmacological characteristics and species-related variations of β3-adrenergic receptors

Summary— Beta-adrenergic receptors (β/-AR) belong to the large multigenic family of receptors coupled to GTP-binding proteins. Three subtypes have been identified: β₁-, β₂- and β₃-AR. Much of the work delineating the precise pharmacological comparison of the three β-ARs has come from investigations with stably transfected Chinese hamster ovary cells (CHO cells). This review discusses the structure and function of β₃-AR in various species and presents new findings on a number of β₃-AR ligands including carazolol, tertatolol and CL 316,243 which were found to be selective and potent β₃-AR agonists and ZD 2079 and salmeterol which appear to display full but non-subtype selective agonistic activity. Species-related variations of the β₃-AR pharmacology have been shown for propranolol and bupranolol. With the ongoing characterization of the β₃-AR at the molecular and cellular level, and with the advent of computer-assisted molecular modelling to aid in the determination of the three-dimensional structure of the receptor, it is thought that novel β₃-AR compounds will become available with improved selectivity and potency.     

Measurement of Plasma 25-Hydroxycholecalciferol in Man

Abstract. A radio-ligand assay for the measurement of 25-hydroxycholecalciferol (25-OH D₃) in human plasma has been devised. Three ml of plasma, with 25-hydroxychole-calciferol-26, 27-H³ (³H-25-OH D₃) added for recovery, was extracted and purified by thin-layer chromatography. The plasma from an osteomalacic man, diluted 1 to 800, was used as a source of binding proteins. After overnight incubation at 4° C bound and free fractions were separated using Florisil. The method has no blank and high sensitivity (2 ng).
Plasma concentration of 25-OH D₃ in normal subjects was 1.50±0.42 (mean ±SD, μg/100ml); in vitamin D deficient patients the values ranged from 0.2 to 0.7 (μg/100 ml.     

Adenylate cyclase activity and cAMP content of human platelets in uraemia

Abstract. We investigated the effects of uraemia and haemodialysis on the basal activity of adenylate cyclase and the cyclic-AMP content of human platelets in patients with end-stage renal insufficiency, patients receiving maintenance haemodialysis, and as controls healthy voluntary subjects.
Basal adenylate cyclase activity in terminal renal disease (creatinine clearance less than 15 ml/min/1·73 m²) was 824 ± SEM 57, in comparison to the healthy subjects with 453 ± SEM 28 ( P < 0·001). We also found significant elevation ( P < 0·001) of platelet cAMP levels as compared to the controls. Basal adenylate cyclase activity and platelet cAMP levels were approximately normal in the dialysed patients.
These results show that uraemic toxins adversely affect the platelet AC-cAMP system, possibly causing impaired platelet aggregation and the bleeding diathesis of uraemia.     

Cytoplasmic regions of the β3 subunit of integrin αIIbβ3 involved in platelet adhesion on fibrinogen under flow conditions

Summary.  Platelet adhesion to surface-bound fibrinogen depends on integrin α_IIbβ₃. In the present study, we investigated the role of the regions ⁷⁴⁹EATSTFT⁷⁵⁶N and ⁷⁵⁵TNITYRG⁷⁶²T of the β₃ cytoplasmic tail in the regulation of platelet adhesion under flow conditions, by introducing peptide mimetics in platelets. Introduction of peptide EATSTFTN (E–N) increased surface coverage by 35%, an effect caused by 25% more adhesion. In contrast, peptide TNITYRGT (T–T) decreased surface coverage by 16%, as a result of 25% less adhesion. An S→P substitution in the E–N peptide, thereby mimicking a mutation in Glanzmann's thrombasthenia, abolished the effect of E–N. A suboptimal concentration of cytochalasin D is known to enhance ligand binding to α_IIbβ₃ in platelet suspensions. Under flow, cytochalasin D (1 µmol L⁻¹) induced 50% more platelet adhesion, with a strong reduction in platelet spreading. Both peptides opposed the increase in adhesion by cytochalasin D and partly (E–N) and completely (T–T) restored platelet spreading. Thus, the ⁷⁴⁹EATSTFT⁷⁵⁶N and ⁷⁵⁵TNITYRG⁷⁶²T regions of β₃ contribute to the regulation of αIIbβ3 anchorage to the cytoskeleton and platelet spreading to an adhesive surface.