Characterisation of postjunctional α-adrenoceptors in isolated human femoral veins and arteries

Summary In order to characterise the pharmacological properties of postjunctional -adrenoceptors, both the contractile effects of -adrenoceptor agonists and the blocking potencies of selective -adrenoceptor antagonists were studied in isolated human femoral veins and arteries.The veins were more sensitive to noradrenaline than the arteries. Guanfacine had a higher intrinsic activity in veins than in arteries, whereas the reverse was true for phenylephrine.The antagonists rauwolscine and yohimbine were more potent against noradrenaline in the veins than in arteries, while corynanthine was equally potent in either tissue. They antagonised the noradrenaline response in a competitive manner. Prazosin proved to be the most potent competitive antagonist in arteries, while in veins it exerted weak and noncompetitive antagonism.The results suggest that the -adrenoceptor population at the postjunctional site differs between human femoral veins and arteries. The veins seem to contain more ₂- than ¹-adrenoceptors postjunctionally, whereas in the arteries the ₂-subtype prevails. The results indicate the possibility of influencing selectively adrenergic reactions in the capacitance and resistance vessels.     

Über die Wirkung von α-Methyl-Dopa auf den Brenzcatechinamingehalt von Meerschweinchenorganen

Zusammenfassung 1. Versuche über die Wirkung von -Methyl-Dopa auf den Brenzcatechinamingehalt von Meerschweinchenorganen haben ergeben, daß Noradrenalin im Herzen, sowie Dopamin und Noradrenalin im Gehirn durch äquimolare Mengen von -Methyl-Noradrenalin bzw. -Methyl-Dopamin ersetzt werden.2. Die Adrenalinverarmung der Nebennieren nach Vorbehandlung mit -Methyl-Dopa wird demgegenüber nur zu einem geringen Teil durch die methylierten Brenzcatechinamine -Methyl-Noradrenalin und -Methyl-Dopamin ausgeglichen. Ein weiteres Brenzcatechinamin konnte nicht nachgewiesen werden, so daß -Methyl-Adrenalin wahrscheinlich nicht gebildet wird.3. Im Meerschweinchenherzen gespeichertes -Methyl-Noradrenalin wird durch Reserpin in vivo schlechter freigesetzt als Noradrenalin.4. Das in isolierten Herzgranula (Sediment 100 000·g) gespeicherte -Methyl-Noradrenalin wird durch Segontin bei der Inkubation in vitro ebenfall schlechter freigesetzt als Noradrenalin aus normalen Herzgranula.5. Der Mechanismus der -Methyl-Dopa-Wirkung wird diskutiert.6. Es wird eine fluorimetrische Methode zur Bestimmung von -Methyl-Noradrenalin angegeben.

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Summary 1. The catecholamine content of guinea pig organs after administration of -methyldopa has been determined. The results show that the loss of noradrenaline from heart and that of noradrenaline and dopamine from brain is compensated by a stoichiometric uptake of -methylnoradrenaline and -methyldopamine respectively.2. On the contrary the loss of adrenaline from the suprarenal medulla induced by pretreatment with -methyldopa is not completely restored by the -methylated amines, -methyldopamine and -methylnoradrenaline. -methyladrenaline could not be detected even by paperchromatography.3. The release of the stored -methylnoradrenaline from guinea pig heart by reserpine is very small in comparison with that of noradrenaline.4. Furthermore only small amounts of the stored -methyl-noradrenaline are released from isolated granules of the guinea pig heart after incubation in vitro with segontin. Whereas the same amount of segontin depleted completely the noradrenaline content of the granules isolated from normal hearts.5. The mechanism of action of -methyldopa is discussed.6. A method for the fluorimetric determination of -methylnoradrenaline is described. It is at first separated from -methyldopamine, dopamine and histamine by column chromatography, condensed with o-phthaldialdehyd and the obtained fluorescense is measured by using an Aminco-Bowman spectrophotofluorimeter.

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Mit 6 Textabbildungen

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Herrn Dr. H. Blaschko zum 65. Geburtstag gewidmet.

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Über einen Teil der Ergebnisse wurde auf der Frühjahrstagung der Deutschen Pharmakologischen Ges. in Mainz, April 1964, berichtet. Naunyn-Schmiedebergs Arch. exp. Path. Pharmak. 247, 297 (1964).

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Ausgeführt mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Quantitative Structure–Activity Relationship Analysis of Combretastatins: A Class of Novel Antimitotic Agents

Combretastatins and their synthetic analogues, having structural features resembling that of colchicine, also have similar modes of action. In this report we have correlated the cytotoxicity of combretastatins against the murine leukemic cell line L1210 with physicochemical parameters such as the summation of the Hansch-Fujita constant, which was used as an index of lipophilicity of the substituent groups on ring A (_a) and ring B (_b), the vector summation of the group dipole moments of ring A (µ_a) and ring B (µ_b), the nature of the linker chain between ring A and ring B (B_t-L), indicator parameters (NOH)_a and (NOH)_b, which represent the number of hydroxyl groups on ring A and ring B, respectively, and the summation of values of the substituents on the linker (_L). Cytotoxicity correlated well with (_b), (NOH)_a, (B_t-L), and (µ_b), and the dependency on (_b) was found to be parabolic.     

Comparative studies on distribution and covalent tissue binding of 2,4,2′,4′- and 3,4,3′,4′-tetrachlorobiphenyl isomers in the rat

The ¹⁴C-labeled tetrachlorobiphenyl (TCB) isomers 2,4,2,4-tetrachlorobiphenyl (2,4,2,4-TCB) and 3,4,3,4-tetrachlorobiphenyl (3,4,34-TCB) were administered orally to rats, and distribution and covalent binding were measured in several organs. Marked differences in distribution and covalent binding of the two TCBs were observed. The accumulation and retention of 2,4,2,4-TCB in adipose tissue were much higher than those of 3,4,3,4-TCB, although the level of radioactivity in the blood was consistently higher in 3,4,3,4-TCB treated rats. The radioactivity bound in covalent linkages with cellular macromolecules in several tissues was also measured. The data obtained indicated that covalent binding was higher in 3,4,3,4-TCB treated rats than in those treated with 2,4,2,4-TCB, particularly in liver and blood components. These results suggest that the two TCB isomers have different pharmacokinetic properties in rats, and the association of covalent binding with 3,4,3,4-TCB-induced toxicities might be important. In addition, we found that repeated oral dosing with the two TCB isomers caused an increase in in vitro liver microsomal generation of reactive metabolites of TCBs, indicating that the microsomal enzyme system is likely to play an important role in the in vivo covalent binding of TCB.     

SK&F 104078, a post-functionally selective α2-adrenoceptor antagonist in the human saphenous vein in vitro

Summary The present study investigated the effects of SK&F 104078 (6-chloro-9-[(3-methyl-2-butenyl)oxy]-3methyl-1H,2,3,4,-tetrahydro-3-benzazapine) at pre- and post functional ₂-adrenoceptors in the human isolated saphenous vein. Noradrenaline (0.001–100 mol/l) produced concentration-dependent contractions of the human saphenous vein which were competitively antagonised by the ₁-adrenoceptor antagonist prazosin (0.01–1.0 mol/l) and the ₂-adrenoceptor antagonist, rauwolscine (0.01–1.0 mol/l), indicating the presence of both post functional ₁- and ₂-adrenoceptors in this preparation. The selective ₂-adrenoceptor agonist, UK-14,304 (0.01–100 mol/l) also produced concentration-dependent contractions of the human saphenous vein which were antagonised by both rauwolscine (0.1 mol/l) and prazosin (0.1 mol/l). In the presence of angiotensin II (0.05 mol/l), which itself produced a transient contraction, rauwolscine (0.1 mol/l) produced a rightward shift of the UK-14,304 concentration-response curve while prazosin (0.1 mol/l) had no effect. SK&F 104078 (10.0 mol/l) under these conditions also produced a rightward shift of the concentration-response curve to UK-14,304, but was at least 100-fold less potent than rauwolscine. At pre functional ₂-adrenoceptors, exogenous noradrenaline (0.01 and 0.1 gmol/l) induced a concentration-dependent inhibition of stimulation-evoked [7-³H]-noradrenaline release from the human saphenous vein in vitro, which was antagonised by rauwolscine (0:1 mol/l) and tolazoline (10.0 mol/l) but not by SK&F 104078 (10.0 gmol/l).Rauwolscine (0.1 mol/l) produced a small increase in stimulation-evoked [7-³H]-noradrenaline release while both tolazoline and SK&F 104078 failed to produce any enhancement in release in the absence of exogenous agonist atconcentrationsupto10 gmol/l.Insummary, noradrenaline and UK-14,304 contracted the human isolated saphenous vein by an action at both postfunctional ₁- and ₂-adrenoceptors. These data demonstrate that SK&F 104078 discriminates between post- and pre-junctional ₂-adrenoceptors in the human isolated saphenous vein. Send offprint requests to M. V. Sennitt at the above address     

Antifungal Activity of a New Triterpenoid Glycoside from Pithecellobium racemosum (M.)

Purpose. In a continuation of our search for novel antifungal compounds from higher plants, the standard extract of the bark of Pithecellobium racemosum was found to have good activity against important AIDS-related opportunistic yeasts. Methods. The extract was subjected to bioguided fractionation using silica gel column chromatography which led to purification of triterpene glycosides. The structures of these compounds were determined by a combination of spectroscopic (IR, NMR, HRMS) and chemical methods. Results. Compound 1 is a new glycoside, 3-O[-L-arabinopyranosyl (1 -2)][-L arabinopyranosyl (1 -6)]2-acetoamido-2-deoxy--D-gluco-pyranosyl oleanolic acid and Compound 2 was identified as the known compound 3-O-[-L-arabinopyranosyl (l-2)]-L-arabinopyranosyl (1-6)] 2-acetamido-2-deoxy--D-glucopyranosyl echinocystic acid. Conclusions. Compound 1 is a new glycoside, 3-O-[-L-arabinopyranosyl (1-2)]-L-arabinopyranosyl (l-6)]-2-acetoamido-2-deoxy--D-glucopyranosyl oleanolic acid and exhibits moderate antifungal activity against T. mentogrophytes, C. albicans and S. cerevisiae with MIC values of 6.25, 12.5 and 12.5 g/ml respectively.     

Protein Aggregates Seem to Play a Key Role Among the Parameters Influencing the Antigenicity of Interferon Alpha (IFN-α) in Normal and Transgenic Mice

Purpose. During long-term treatment of various malignant or viral diseases with IFN- up to 20% of patients develop anti-IFN- antibodies for as yet unknown reasons. Methods. To address this issue, a mouse model using Balb/C mice was established and the relevance of several potentially anti-IFN- antibodies inducing factors was studied. Results. The model revealed that both a higher frequency of injections and a higher dosage of IFN- were more immunogenic and that the route of administration affected the antibody response to IFN-. The intrinsic immunostimulatory activity of IFN- itself also enhanced the immune response. IFN- protein aggregates (IFN--IFN- and human serum albumin (HSA)-IFN- aggregates), which were recently identified in all marketed IFN- products, were significantly more immunogenic than IFN- monomers. These aggregates broke the tolerance against human IFN- monomers in human IFN- transgenic mice. Conclusions. Based on these animal studies it is proposed that the immune response to IFN- in humans is most probably elicited by a combination of several factors among which IFN- protein aggregates seem to play a key role.     

EEG spectral analysis for the evaluation of the central effects of δ6-tetrahydrocannabinol in rabbits

The effects of ⁶-THC on the frequency spectrum of the hippocampal EEG were examined with the assistance of an electronic integrator. Six rabbits bearing chronically implanted cortical and hippocampal electrodes were dosed intravenously with ⁶-THC (2.5% solution in polyethylene glycol 300; doses of 10, 50, 100, 250 and 1000 g/kg) once a week. A comparison of epochs of arousal in the pre-drug control and post-drug periods demonstrated that a dose as low as 50 g/kg produced a consistent, statistically significant diminution in power of the 7, 8, 9 Hz frequencies of the hippocampal EEG, with 8 Hz the most sensitive. Doses above 250 g/kg produced an overall decrease in the power spectrum from 7 to 27 Hz.Spectral analysis of the EEG offers a method which is sufficiently sensitive to reveal a central effect of ⁶-THC in rabbits at doses equivalent to the human threshold for psychic effects.Presented, in part, at the VIIIth International Congress of Electroencephalography and Clinical Neurophysiology, Marseilles, France, September 1–7, 1973.M. D. W. was supported by the Medical Research Council of Canada during the tenure of this work.The technical assistance of Mr. E. Deodati is gratefully acknowledged.     

Assessing the pharmaceutical care needs of asthmatic patients

Objectives: To measure patients perceptions of their care needs, by developing a tool to assess these needs and evaluate its utility in community pharmacy practice.Method: A survey tool comprising 37 items was developed to assess asthmatic patients perceptions of their health-related needs, using data from literature reviews and expert opinions. The tool was piloted on 25 patients to ensure the content of the questionnaire was valid. Changes were made following piloting and the modified tool was then tested in the main study, on 101 patients from thirteen community pharmacies in Portugal. Data from this phase were subjected to factor analysis and reliability testing.Results: 118 asthmatic patients were recruited, of which 101 questionnaires were eligible for analysis. From these, 40 were male (39.6%) and 61 were female (60.4%). The mean age of respondents was 41 years (sd=19.02). The first changes made to the survey tool included the adding of items relevant to patients recruited in the pilot and the simplification of the scaling used. The survey tool was then subjected to factor analysis and reliability testing. Six scales emerged, which described the need for GP support, specialist support, pharmacist support, nurse support, other carers support and written support. Internal consistency was good (Cronbachs coefficient alpha ranged from 0.81 to 0.93). Although there were no significant associations between educational level and other factors, other attributes influenced the communication between pharmacist and physician (²=6.972; P=0.031). Patients with a lower level of education (up to six years) valued communication between these two professionals more than among patients with higher education. The patients age group was associated with an expressed need for explanation of inhaler technique (²=6.494; P=0.039). There was extended need in both oldest and youngest patients. There was a significant difference between high and low scorers to the factor pharmacists role in asthma (F1) and patients treated by either specialist or GP (²=4.935; P=0.026). There were differences between those who were bothered by their asthma or not and their perceptions of Pharmacists ideal role in asthma (F1 & 3) (²=5.967; P=0.051).Conclusion: The tool needs further development to ensure its validity and utility in practice. This will provide greater insight into patients perceptions of their healthcare needs, which can allow health professionals to target their interventions. Such a tool may then be used in pharmacies that intend to change their current practice, to raise pharmacists awareness ofpatients demands. Developing ways to meet those needs will ultimately lead to an increased quality service and therefore client satisfaction.     

Risk factors for the development of adverse drug events in hospitalized patients

Adverse drug events in hospitalized patients lead to increased morbidity, mortality and costs. Early detection of adverse drug events could aid in the prevention of these adverse outcomes. A costeffective system for the early detection of adverse drug events should focus on high risk patients. A study was set up with the primary aim to identify characteristics that are associated with the development of adverse drug events (ADEs) in hospitalized patients.ADE reports were gathered from physicians and nurses (spontaneous reports) and from patients after intensive ward interviews by hospital pharmacists. All patients admitted to the internal medicine wards of two Dutch hospitals, during a two month period, were included.The following characteristics were analyzed for their potential relationship to the occurence of ADEs: age (categorized), gender, number of drugs prescribed during hospital stay, types of drugs used and changes in drug use on admission.Age was found to be inversely associated with the development of ADEs (OR 0.36, CI 0.210.61 for age category > 80 years; OR 0.56; CI 0.311.02 for age category 7580 years and OR 0.69; CI 0.421.11 for age category 6074 years). Furthermore, statistically significant associations were found for the number of drugs prescribed per hospitalized patient (for the class of 46 drugs per patient OR 2.61, CI 1.325.18), for newly prescribed drugs (OR 6.65, CI 2.6316.81) and for the cessation of drugs on hospital admission (OR 1.50, CI 1.022.20). The use of gastrointestinal drugs (OR 2.13, CI 1.323.45), central nervous system drugs (OR 1.66, CI 1.072.57) and antibiotics (OR 2.44, CI 1.653.60) were associated with the development of ADEs, when compared to all other drugs taken by the patients.In this study, the most important risk factors are the number of drugs used per patient and the starting of a new drug during hospitalization. As most hospitalized patients start new drug therapies while in hospital, this seems an inappropriate focus. However, careful monitoring of patients using more than 7 drugs at a time may be possible in a costeffective system for the early detection of ADEs.     

The effect of gamma-butyrolactone on locomotor activity in the rat

The effect of -butyrolactone (GBL) on locomotor activity in the rat was studied. Low doses of GBL (100 and 200 mg/kg) had a biphasic effect on activity. Initially, the activity of the rats was reduced, and this reduction was then followed by a period of hyperactivity. The effect of -flupenthixol (50 g/kg -FPT), atropine (10 mg/kg), benztropine (25 mg/kg), protriptyline (15 mg/kg), and clomipramine (25 mg/kg) was investigated on this biphasic effect. -FPT reduced the hyperactivity while benztropine potentiated it; atropine, clomipramine, and protriptyline had little effect. It is concluded that the increase in activity could be due to a release of dopamine.     

Interaction of adenine nucleotides,UTP and suramin in mouse vas deferens: suramin-sensitive and suramin-insensitive components in the contractile effect of ATP

Summary Effects of various nucleotides, nucleosides and noradrenaline on smooth muscle tension were studied in the isolated mouse vas deferens. ,-Methylene-ATP, ATPS, noradrenaline, ATP and UTP elicited contraction, with potency decreasing in that order; there was no contractile response to adenosine or uridine (up to 100 mol/l). Prolonged incubation with ,-methylene-ATP (concentration increased stepwise from 0 to 15 mol/l) selectively reduced contractions induced by ATP and UTP but not those induced by noradrenaline, and there was cross-tachyphylaxis between ATP and UTP. Suramin (10–300 mol/l) did not alter the response to noradrenaline but shifted the concentration-response curves for ,-methylene-ATP, ATPS, UTP and lower concentrations of ATP (0.1–1 ol/l) to the right. The pA₂-values of suramin were 5.2 against ,-methylene-ATP, 4.8 against ATPyS, 5.1 against UTP and 5.4 against lower concentrations of ATP. The effects of higher concentrations of ATP were largely resistant to suramin. The results indicate that the mouse vas deferens possesses contraction-mediating smooth muscle P_2X-receptors. UTP also acts at this receptor, and there is no evidence for a separate UTP receptor. The selective inhibition of nucleotide- but not noradrenaline-induced contractions by suramin confirms the view that suramin is a selective P₂-antagonist. The resistance against suramin of part of the effect of ATP suggests that ATP activates a suramin-insensitive site in addition to the P_2X-receptor.Send offprint requests to I. von Kügelgen at the above address     

Identification of the Diastereomers of Pentobarbital N-Glucosides Excreted in Human Urine

A study was undertaken to determine if humans excreted pentobarbital N-glucosides as urinary metabolites following oral administration of pentobarbital. (lRS,5RS)-l--D-Glucopyranosyl) pentobarbital ((lRS,5RS)-PTBG) was isolated from the urine of one subject. The two diastereomers, (lRS,5R)-PTBG and (lRS,5S)-PTBG were separated and found to be identical to synthetic standards when compared using HPLC retention times coupled with UV (with and without post-column ionization) and mass spectrometry (HPLC/ MS). A HPLC method was developed for detecting and quantifying (lRS,5R)-PTBG, (lRS,5S)-PTBG and pentobarbital in urine. Following a single oral dose of sodium pentobarbital to male subjects (n = 6), 1.6–6.2% of the pentobarbital dose was excreted as (lRS,5S)-PTBG over 60 hours. (lRS,5R)-PTBG was also detected in one subject and accounted for 0.3% of the pentobarbital dose. Using a modified HPLC system, the four pentobarbital N-glucosides were resolved and analysis of a partially purified pentobarbital N-glucoside extract from one subject indicated that only (lR,5R)-PTBG and (lS,5S)-PTBG could be detected as urinary excretion products. These results indicate that the side chain chirality of pentobarbital may influence the observed enantioselectivity for the formation and/or urinary excretion of the pentobarbital N-glucosides.     

Low-affinity interactions of BODIPY-FL-GTPγS and BODIPY-FL-GppNHp with G<Subscript>i</Subscript>- and G<Subscript>s</Subscript>-proteins

BODIPY-FL-guanosine 5'-[-thio]triphosphate (B-GTPS) and BODIPY-FL-guanosine 5'-[,-imido]triphosphate (B-GppNHp) induce fluorescence changes upon binding to purified G_s/G_i-proteins and were suggested to serve as probes for monitoring receptor-mediated G-protein activation. However, B-GTPS and B-GppNHp bound to receptor-G_s/G_i fusion proteins expressed in Sf9 cell membranes with 1,100- to 5,600-fold- and 17- to 55-fold lower affinity than GTPS and GppNHp, respectively. The affinity of B-GTPS/B-GppNHp for G_s/G_i-proteins was considerably lower than the affinity of N-methylanthraniloyl (MANT)-substituted GTP analogs for G_s/G_i-proteins. B-GTPS/B-GppNHp were much less potent than GTPS/GppNHp at regulating adenylyl cyclase (AC) via G_s- and G_i-proteins. B-GTPS/B-GppNHp were similarly efficient as GTPS/GppNHp at activating G_i, but less efficient at activating G_s. In contrast to MANT-GTPS/MANT-GppNHp, B-GTPS/B-GppNHp were inefficient at directly inhibiting AC. In conclusion, the bulky BODIPY group strongly reduces the affinity of GTPS/GppNHp for G-proteins, limiting the use of B-GTPS/B-GppNHp as fluorescence probes.Abbreviations AC Adenylyl cyclase - ₂AR ₂-Adrenoceptor - ₂AR-G_olf Fusion protein consisting of the ₂-adrenoceptor and G_olf - ₂AR-G_sL Fusion protein consisting of the ₂-adrenoceptor and the long splice variant of G_s - ₂AR-G_sS Fusion protein consisting of the ₂-adrenoceptor and the short splice variant of G_s - B-GppNHp BODIPY-FL-guanosine 5'-[,-imido]triphosphate - B-GTPS BODIPY-FL-guanosine 5'-[-thio]triphosphate - FPR-G_i1,2,3 Fusion protein consisting of the formyl peptide receptor and G_i1, G_i2 or G_i3 - G Unspecified G-protein -subunit - G_i Inhibitory G-protein of adenylyl cyclase - G_olf Olfactory G-protein that activates adenylyl cyclase - G_s Stimulatory G-protein of adenylyl cyclase - G_sL Long splice variant of the stimulatory G-protein of adenylyl cyclase, G_s - G_sS Short splice variant of the stimulatory G-protein of adenylyl cyclase, G_s - GppNHp Guanosine 5'-[,-imido]triphosphate - GTPS Guanosine 5'-[-thio]triphosphate - M-GppNHp 2'(3')-O-(N-methylanthraniloyl)-guanosine 5'-[,-imido]triphosphate (MANT-GppNHp) - M-GTPS 2'(3')-O-(N-methylanthraniloyl)-guanosine 5'-[-thio]triphosphate (MANT-GTPS)     

Involvement of tumor necrosis factor-α in sulfur mustard-induced skin lesion; effect of topical iodine

Sulfur mustard (SM), also termed mustard gas, is a potent vesicant that elicits an inflammatory response upon exposure of the skin. Evaluation of mouse ear 3 h after SM exposure revealed acute inflammatory-cell aggregates in the vascular beds accompanied by strongly TNF--positive neutrophils. Eight hours after SM exposure, this phenomenon became intensified and associated with infiltration into the adjacent dermis. In ear skin topically treated with iodine, however, no inflammatory cells were observed 3 h after SM exposure; 8 h postexposure, blood vessels contained very few TNF--positive inflammatory cells. Since TNF- induction was shown to be associated with reactive oxygen species production, we studied the effect of iodine on activated peritoneal mouse neutrophils. Iodine elicited a concentration-dependent reduction in the oxidative burst of activated neutrophils. Iodine also scavenged hydroxyl radicals generated by glucose oxidase in a concentration-dependent manner. The involvement of TNF- in SM-induced skin toxicity was confirmed by reduction of 49 and 30% in ear edema following administration of 1 and 2 g anti-TNF- antibodies, respectively. These findings were corroborated by quantitative analysis of the histological findings showing 46% reduction in acute inflammation and no signs of subacute inflammation in the treated group, in contrast to the control group treated with SM only. Other epidermal (microblister formation, ulceration, and necrosis) and dermal (neutrophilia, hemorrhage, and necrosis) parameters also showed marked reductions in the antibodies-treated group in comparison to controls. The combination of iodine and antiTNF- antibodies might constitute a new approach for treatment of SM-exposed individuals.U. Wormser is affiliated with David R. Bloom Center for Pharmacy at The Hebrew University.     

Binding of aprindine and moxaprindine to human serum, α1-acid glycoprotein and serum of healthy and diseased humans

Summary A comparison was made between the binding of the anti-arrhythmic agents aprindine and moxaprindine to human serum, to human serum albumin (HSA), to ₁-acid glycoprotein (₁-AGP) and to a mixture of HSA and ₁-AGP. In serum from healthy volunteers (n=4) the binding of aprindine-HCl 5 µg/ml (13.8 µM) was 93.8% (SD±1.0), and that of moxaprindine-HCl 5 µg/ml (12.8 µM) was 94.1% (SD±1.1). Their binding to the mixture of ₁-AGP and albumin approximated their binding to serum. For ₁-AGP, the binding was similar for both compounds, whereas for HSA the binding of aprindine was more pronounced than that of moxaprindine: for both products the affinity coefficient for binding to ₁-AGP was about 100 times greater than that for binding to albumin. In serum from rheumatoid patients and from patients with renal failure a small but significant increase in binding of aprindine and moxaprindine was observed, approximately 1%. Increased and decreased binding was seen in serum from cirrhotic patients; for example, for aprindine the range in cirrhosis was 96.7%–79.8%, and the range in controls was 95.0%–92.4%. Free drug fraction and ₁-AGP concentration were inversely correlated. The results show that ₁-AGP plays an important role in the binding of aprindine and moxaprindine, and that alteration in the binding of the two compounds in disease states to a large extent can be explained by changes in serum ₁-AGP concentration.     

Possible subdivision of postsynaptic α-adrenoceptors mediating pressor responses in the pithed rat

Summary Additional evidence has been obtained indicating a possible subclassification of postsynaptic -adrenoceptors into ₁ and ₂-subtypes. The pressor responses to the -adrenoceptor agonists L-phenylephrine and guanfacine were quantified after i.v. administration to pithed rats. The -sympatholytic drug yohimbine (1 mg/kg) displaced both dose-response curves to the right, but the effect was greatest for guanfacine. After prazosin (0.1 mg/kg) a 53-fold shift to the right was noticed for the dose-response characteristic of L-phenylephrine. Prazosin antagonized the effect of only the higher doses of guanfacine. The findings indicate that L-phenylephrine and prazosin preferentially interact with ₁-adrenoceptors as agonist and antagonist, respectively. Yohimbine proved less selective than prazosin, but preferentially blocks postjunctional ₂-adrenoceptors in the vascular wall. The results obtained with guanfacine may be interpreted to indicate that this drug acts on ₂-adrenoceptors at lower doses and additionally stimulates ₁-adrenoceptors at higher ones. Preliminary findings with corynanthine and rauwolscine support this interpretation.     

Can digoxin prescribing be improved? A comparison between intuitive and assisted dose selection

Summary 37 patients on maintenance digoxin therapy were observed in hospital over an 8 day period. From day 1 to day 8 measurements of plasma digoxin and serum creatinine indicated that these patients were in the equilibrium state with regard to digoxin levels and renal function. Assuming a linear relationship between dose and plasma concentration, it was possible to calculate the doses which would have produced plasma concentrations of 1.5 ng/ml, and at the limits of the usual therapeutic range, 0.8 and 2.0 ng/ml. Doses obtained from six prescribing aids and those prescribed intuitively by the doctor were then compared. None of the methods used would have resulted in plasma digoxin concentrations within the usual therapeutic range in more than 57% of the patients. The physicians' intuitive choice appeared to be better than the doses estimated from prescribing aids, in that they were correct as often as any assisted method, and when wrong tended to prescribe too low rather than too high. The prescribing aids tended to overestimate dosage in many patients, as high as 65% with one. Plasma digoxin concentration measurement would appear to be the only way to ensure adequate therapeutic efficacy and avoid toxicity in patients receiving maintenance digoxin.     

Activation of β2-adrenoceptors by isoprenaline and adrenaline enhances noradrenaline release in cortical kidney slices of young spontaneously hypertensive rats

Summary The aim of the present study was to investigate -adrenoceptor modulation of noradrenaline release from sympathetic nerves in superfused cortical kidney slices of 4-week-old spontaneously hypertensive rats (SHR) and age-matched controls (WKY). After preincubation with ³H-noradrenaline the kidney slices were electrically stimulated in superfusion chambers. The stimulation induced (S-I) outflow of radioactivity was mainly composed of unmetabolized 3H-noradrenaline in both strains and thus taken as an index of noradrenaline release. There was a frequency-dependent (1.25–20 Hz) increase in the S-1 outflow of radioactivity. At all stimulation frequencies tested S-I outflow of radioactivity was similar or even slightly lower in SHR than in WKY kidney slices in either the absence or presence of cocaine (10 mol/l). The non-selective -adrenoceptor agonists isoprenaline (0.l gmol/1) and adrenaline (0.01 and 0.1 mol/l) enhanced S-I outflow of radioactivity. The facilitatory effects of isoprenaline (0.1 mol/l) and adrenaline (0.1 mol/l) were blocked by the selective ₂-adrenoceptor antagonist ICI 118551 (0.1 mol/l) but not by the selective ₁-adrenoceptor antagonist atenolol (0.3 mol/l). The cell-permeable CAMP analogue 8-bromo-cAMP (300 mol/l) enhanced S-1 outflow of radioactivity to a similar extent in both SHR and WKY kidney slices. A combination of 8-bromo-cAMP (300 mol/l) and adrenaline (0.1 mol/l) did not enhance S-1 outflow of radioactivity to a greater extent than 8-bromo cAMP (300 mol/l) alone in both strains. However, the facilitatory effects of isoprenaline (0.1 mol/l) and adrenaline (0.1 mol/l) but not that of adrenaline (0.01 mol/l) were significantly greater in SHR than in WKY. The results suggest that stimulation of prejunctional ₂-adrenoceptors by adrenaline even in the absence of a-adrenoceptor blockade enhances noradrenaline release in kidney cortex of young SHR and WKY. This ₂-adrenoceptor mediated effect may possibly be dependent on cAMP formation. The greater facilitatory effects of isoprenaline (0.1 mol/l) and adrenaline (0.1 mol/l) in SHR as compared to WKY are in accord with receptor binding studies which show a higher density of ₂-adrenoceptors in SHR than in WKY kidney cortex.Abbreviations SHR Spontaneously hypertensive rats - WKY WistarKyoto rats - cAMP 3-5-cyclic adenosine monophosphate - S-I stimulation induced Send offprint requests to: L. C. Rump     

The effect of phenytoin and metamphetamine on spinal motor activity

Summary The investigation was initiated by the idea that reserpine might exert its action on spinal motor activity through facilitatory impulses in descending pathways to the spinal motoneurones. Therefore, the effect of conditioning by repetitive stimulation of descending and segmental pathways on and reflex discharges was studied in the rat. Conditioning by stimulation of the dorsolateral funiculus increased a and decreased reflex discharge. Conditioning by stimulation of the dorsal funiculus increased reflex discharge without changing reflex activity. In partially or totally spinalized preparations, conditioning by repetitive stimulation of the same dorsal root to which the test stimulus was applied, produced an increase in a reflex activity which was associated with a decrease in motor activity. In the preparations with an intact neuraxis, repetitive stimulation of the dorsal root facilitating reflex discharge did not change motor activity. motor activity also remained unchanged when reflex discharge was inhibited by repetitive stimulation of the dorsal root in the intact or totally spinalized preparation.Phenytoin 50 mg/kg increased the unconditioned response in all types of preparations, apart from that in which the dorsal funiculus was isolated. Facilitation of reflex discharge elicited by repetitive stimulation of segmental and descending pathways was depressed by phenytoin, whereas inhibition remained unchanged.Metamphetamine 2 mg/kg increased the unconditioned reflex discharge in all types of preparations, and decreased the response in the preparations with an intact neuraxis and also in those in which the dorsal funiculus was isolated. Metamphetamine did not depress the facilitatory or inhibitory effects produced by repetitive stimulation of descending or segmental pathways.From the results obtained it is concluded that reserpine rigidity in the rat may be mediated by an increased facilitatory impulse input reaching the a motoneurones by way of descending pathways in the dorsolateral column of the spinal cord, and that phenytoin may antagonize, at least in part, the effect of reserpine by a depressant action on facilitatory processes at the spinal level, whereas abolition of reserpine rigidity produced by metamphetamine must be due to a supraspinal site of action of this drug.Supported by a grant of the Deutsche Forschungsgemeinschaft.