An innovative method to strengthen evidence for potential drug safety signals using Electronic Health Records.

Reports from spontaneous reporting systems (SRS) are hypothesis generating. Additional evidence such as more reports is required to determine whether the generated drug-event associations are in fact safety signals. However, underreporting of adverse drug reactions (ADRs) delays signal detection. Through the use of natural language processing, different sources of real-world data can be used to proactively collect additional evidence for potential safety signals. This study aims to explore the feasibility of using Electronic Health Records (EHRs) to identify additional cases based on initial indications from spontaneous ADR reports, with the goal of strengthening the evidence base for potential safety signals. For two confirmed and two potential signals generated by the SRS of the Netherlands Pharmacovigilance Centre Lareb, targeted searches in the EHR of the Leiden University Medical Centre were performed using a text-mining based tool, CTcue. The search for additional cases was done by constructing and running queries in the structured and free-text fields of the EHRs. We identified at least five additional cases for the confirmed signals and one additional case for each potential safety signal. The majority of the identified cases for the confirmed signals were documented in the EHRs before signal detection by the Dutch Medicines Evaluation Board. The identified cases for the potential signals were reported to Lareb as further evidence for signal detection. Our findings highlight the feasibility of performing targeted searches in the EHR based on an underlying hypothesis to provide further evidence for signal generation.

Population pharmacokinetics of treosulfan in paediatric patients undergoing hematopoietic stem cell transplantation.

AIMS: Treosulfan is an alkylating agent increasingly used prior to haematopoietic stem cell transplantation. The aim of this study was to develop a population pharmacokinetic (PK) model of treosulfan in paediatric haematopoietic stem cell transplantation recipients and to explore the effect of potential covariates on treosulfan PK. Also, a limited sampling model (LSM) will be developed to accurately predict treosulfan exposure suitable for a therapeutic drug monitoring setting. METHODS: In this multicentre study, 91 patients, receiving a total dose of 30, 36 or 42 g/m2 treosulfan, administered over 3 consecutive days, were enrolled. A population PK model was developed and demographic factors, as well as laboratory parameters, were included as potential covariates. In addition, a LSM was developed using data from 28 patients. RESULTS: A 2-compartment model with first order elimination best described the data. Bodyweight with allometric scaling and maturation function were identified as significant predictors of treosulfan clearance. Treosulfan clearance reaches 90% of adult values at 4 postnatal years. A model-based dosing table is presented to target an exposure of 1650 mg*h/L (population median) for different weight and age groups. Samples taken at 1.5, 4 and 7 hours after start of infusion resulted in the best limited sampling strategy. CONCLUSIONS: This study provides a treosulfan population PK model in children and captures the developmental changes in clearance. A 3-point LSM allows for accurate and precise estimation of treosulfan exposure.

Real-World Metastatic Renal Cell Carcinoma Treatment Patterns and Clinical Outcomes in The Netherlands.

The number of treatment options for patients with metastatic renal cell carcinoma (mRCC) has significantly grown in the last 15 years. Although randomized controlled trials are fundamental in investigating mRCC treatment efficacy, their external validity can be limited. Therefore, the efficacy of the different treatment options should also be evaluated in clinical practice. We performed a chart review of electronic health records using text mining software to study the current treatment patterns and outcomes. mRCC patients from two large hospitals in the Netherlands, starting treatment between January 2015 and May 2020, were included. Data were collected from electronic health records using a validated text mining tool. Primary endpoints were progression-free survival (PFS) and overall survival (OS). Statistical analyses were performed using the Kaplan-Meier method. Most frequent first-line treatments were pazopanib (n = 70), sunitinib (n = 34), and nivolumab with ipilimumab (n = 28). The overall median PFS values for first-line treatment were 15.7 months (95% confidence interval [95%CI], 8.8-20.7), 16.3 months (95%CI, 9.3-not estimable [NE]) for pazopanib, and 6.9 months (95% CI, 4.4-NE) for sunitinib. The overall median OS values were 33.4 months (95%CI, 28.1-50.9 months), 39.3 months (95%CI, 29.5-NE) for pazopanib, and 28.1 months (95%CI, 7.0-NE) for sunitinib. For nivolumab with ipilimumab, median PFS and median OS were not reached. Of the patients who finished first- and second-line treatments, 64 and 62% received follow-up treatments, respectively. With most patients starting on pazopanib and sunitinib, these real-world treatment outcomes were most likely better than in pivotal trials, which may be due to extensive follow-up treatments.

Effectiveness and toxicity of lenvatinib in refractory thyroid cancer: Dutch real-life data.

OBJECTIVE: The SELECT trial showed progression-free survival (PFS) benefit for lenvatinib for advanced radioiodine-refractory differentiated thyroid cancer (RAI-refractory or RR-DTC) patients, on which current clinical practice is based. We assessed whether the effectiveness and toxicity of lenvatinib in real-life clinical practice in the Netherlands were comparable to the pivotal SELECT trial. METHODS: From three Dutch centres Electronic Health Records (EHRs) of patients treated in the lenvatinib compassionate use program or as standard of care were reviewed and checked for SELECT eligibility criteria. Baseline characteristics, safety, and efficacy measures were compared and PFS and overall survival (OS) were calculated. Furthermore, PFS was compared to estimates of PFS reported in other studies. RESULTS: A total of 39 DTC patients with a median age of 62 years were analysed. Of these, 27 patients (69%) did not fulfil the SELECT eligibility criteria. The most common grade ≥3 toxicities were hypertension (n = 11, 28%), diarrhoea (n = 7, 18%), vomiting (n = 4, 10%), and gallbladder disease (n = 3, 8%). Median PFS and median OS were 9.7 (95% confidence interval (CI): 4.0-15.5) and 18.3 (95% CI: 4.9-31.7) months, respectively, response rate was 38% (95% CI: 23-54%). PFS in the Dutch real-life situation was comparable to previous real-life studies, but inferior to PFS as shown in the SELECT trial (P = 0.04). CONCLUSIONS: PFS in our non-trial population was significantly shorter than in the SELECT trial population. In the interpretation of results, differences in the real-life population and the SELECT study population regarding patient characteristics should be taken into account.

Results of streamlined regional ambulance transport and subsequent treatment of acute abdominal aortic aneurysms.

OBJECTIVE: To describe the triage of patients operated for non-ruptured and ruptured abdominal aortic aneurysms (AAAs) before the endovascular era. DESIGN: Retrospective single-centre cohort study. METHODS: All patients treated for an acute AAA between 1998 and 2001 and admitted to our hospital were evaluated in the emergency department for urgent AAA surgery. All time intervals, from the telephone call from the patient to the ambulance department, to the arrival of the patient in the operating theatre, were analysed. Intraoperative, hospital and 1-year survival were determined. RESULTS: 160 patients with an acute AAA were transported to our hospital. Mean (SD) age was 71 (8) years, and 138 (86%) were men. 34 (21%) of these patients had symptomatic, non-ruptured AAA (sAAA) and 126 patients had ruptured AAA (rAAA). All patients with sAAA and 98% of patients with rAAA were operated upon. For the patients with rAAA, median time from telephone call to arrival at the hospital was 43 min (interquartile range 33-53 min) and median time from arrival at the hospital to arrival at the operating room was 25 min (interquartile range 11-50 min). Intraoperative mortality was 0% for sAAA and 11% for rAAA (p = 0.042), and hospital mortality was 12% and 33%, respectively (p = 0.014). CONCLUSIONS: A multidisciplinary unified strategy resulted in a rapid throughput of patients with acute AAA. Rapid transport, diagnosis and surgery resulted in favourable hospital mortality. Despite the fact that nearly all the patients were operated upon, survival was favourable compared with published data.

Effects of hyperthermic isolated limb perfusion with recombinant tumor necrosis factor alpha and melphalan on the human fibrinolytic system.

This study was undertaken to determine the effects on systemic fibrinolysis of hyperthermic isolated limb perfusion with recombinant tumor necrosis factor alpha (r-TNF-alpha) and melphalan, with or without pretreatment with recombinant IFN-gamma (r-IFN-gamma). Twenty patients were treated with r-TNF-alpha and melphalan; four patients, treated with melphalan only, served as controls. Of the twenty patients treated with both r-TNF-alpha and melphalan, eight received r-IFN-gamma for two days before the perfusion and as a bolus into the perfusion circuit. A significant leak of r-TNF-alpha from the perfusion circuit to the systemic circulation was observed in all r-TNF-alpha-treated patients (mean maximum TNF-alpha, 87,227 ng/liter versus 31 ng/liter in controls; P < 0.002). In these patients, but not in controls, there was an almost instantaneous rise in systemic tissue plasminogen activator activity (from 0.26 to 5.28 IU/ml in 90 min), causing activation of fibrinolysis. After a delay of 90 min, plasminogen activator inhibitor-1 (PAI-1) antigen rose to high levels in the r-TNF-alpha-treated group (mean maximum PAI-1, 1652 ng/ml versus 211 ng/ml in controls; P < 0.02), associated with a sharp decrease of tissue plasminogen activator activity and a slower decrease of plasminogen-antiplasminogen complexes (from 5.28 to 0.02 IU/ml in 2 h and from 1573 to 347 micrograms/liter in 22 h, respectively). No additional effect of IFN-gamma pretreatment on fibrinolysis could be demonstrated. These results suggest that in isolated limb perfusion with r-TNF-alpha and melphalan an initial activation of systemic fibrinolysis, induced by leakage of r-TNF-alpha from the perfusion circuit, is set off by a subsequent inhibition of the fibrinolytic system by PAI-1. This large increase in PAI-1 could place the patient at risk for deposition of microthrombi in the systemic circulation.

Intravenous busulfan in children prior to stem cell transplantation: study of pharmacokinetics in association with early clinical outcome and toxicity.

We studied the pharmacokinetics of intravenous busulfan (Bu) in children in order to further optimize intravenous Bu dosing in relation to toxicity and survival. A total of 31 children undergoing Bu-based conditioning for allogeneic SCT were enrolled in a study. The starting dose was 1.0 mg/kg (age < 4 years) and 0.8 mg/kg (age > or =4 years), four doses per day during 4 days. Dose adjustment was allowed up to a maximum dose of 1.0 mg/kg per dose if the target area under the serum concentration-time curve (AUC) was not reached. Pharmacokinetic studies were performed after the first dose. Donor engraftment was established in 28 out of 31 patients. The average AUC after the first dose was the same in children < 4 years as in children > or =4 years. Mean clearance was higher in children < 4 years than in children > or =4 years. In 35% of all patients, total AUC was within the target AUC. The other children's AUCs were below the target range. No relationships were found between systemic exposure to Bu and toxicity or clinical outcome. We concluded that, in accordance with previous data, within the observed AUCs no clear relationship was observed between Bu AUC and outcome with respect to toxicity, engraftment and relapse.

Retransplantation of the liver in children.

BACKGROUND: Because of the poor outcome of hepatic retransplantation, it is still debated whether this procedure should be performed in an era of donor organ scarcity. The aim of this study was to analyze outcome of hepatic retransplantation in children, to identify risk factors influencing this outcome, and to assess morbidity and causes of death. METHODS: A series of 97 children after a single transplantation and 34 children with one retransplantation was analyzed. RESULTS: The 1-, 3-, and 5-year survival of children with a retransplantation was 70, 63, and 52%, respectively, compared with 85, 82, and 78%, respectively, for children after a single transplantation (P=0.009). Survival of children with a retransplantation within 1 month after primary transplantation was worse (P=0.007) and survival of children with a late retransplantation was comparable (P=0.66) with single transplantation. In early retransplantations, the Child-Pugh score was higher, donors were older and weighed more, and more technical variant liver grafts were used compared with single transplantations. Biliary atresia and a high Child-Pugh score were associated with decreased patient survival after retransplantation. Sepsis was the most important complication and cause of death after retransplantation. CONCLUSIONS: Retransplantation is a significant event after pediatric liver transplantation. Outcome after hepatic retransplantation in children is inferior compared with single transplantation. This difference is explained by low survival after early retransplantation and can be explained by the poor clinical condition of the children at time of retransplantation, especially in children with biliary atresia, and by the predominant use of technical variant liver grafts in retransplantations.

Prognostic factors for long-term actual patient survival after orthotopic liver transplantation in children.

BACKGROUND: Orthotopic liver transplantation has become the treatment of choice for children with end-stage liver disease. Although results have improved the last decades, still a considerable number of children die after transplantation. The aim of this study was to analyze long-term actual survival and to identify prognostic factors for such survival rates. METHODS: A consecutive series of 66 children receiving transplants who had or could have had a follow-up of at least 5 years was retrospectively analyzed. Actual survival and prognostic factors in relation to patient, donor, and operation related variables were assessed after multivariate analysis. RESULTS: Actual 1-, 3-, and 5-year patient survival was 86%, 79%, and 73%, respectively. A high Child-Pugh (C-P) score or C-P class C, high donor age, high blood loss index, and retransplantation were predictive factors for actual patient survival. A high blood loss index was correlated with biliary atresia, low recipient age and weight, and with previous upper abdominal operations. The duration of stay of the donor at the intensive care unit (ICU) was a predictive factor for retransplantation. CONCLUSIONS: Children with diseases eligible for liver transplantation should be seen early in the course of their disease in a transplantation center. All possible measures should be taken during the transplantation procedure to keep the blood loss at a minimum. Children with biliary atresia deserve special attention in this respect. The choice of donors has implications for survival.

Analysis of survival and morbidity after pediatric liver transplantation with full-size and technical-variant grafts.

BACKGROUND: To alleviate the shortage of size-matched whole-donor organs, too-large-for-size cadaveric donor grafts are modified by liver resection techniques. These modifications result in technical-variant liver transplantation (TVLTx). Patient and graft survival rates after TVLTx are considered comparable to those after full-size liver transplantation (FSLTx). However, morbidity after TVLTx is often underexposed. The aim of this study was to analyze the results of FSLTx and TVLTx in terms of patient and graft survival rates and morbidity. METHODS: A consecutive series of 97 primary and elective pediatric liver transplantations performed in a single center was retrospectively analyzed. Forty-seven children had a FSLTx and 50 a TVLTx (38 reduced-size liver grafts and 12 split-liver grafts). The overall median follow-up period was 3.5 years. RESULTS: There were no differences in patient and graft survival rates between FSLTx and TVLTx. However, after TVLTx there was a significantly higher complication rate (1.42 vs. 0.81 after FSLTx). TVLTx is more hampered by biliary complications (30% vs. 17%), expressed by a higher incidence of cholangitis and leakage of bile. These complications led to a significantly higher incidence of sepsis (44% vs. 19%) and a significantly higher intervention rate (0.40 vs. 1.28) after TVLTx. There was no difference in the incidence of retransplantations between FSLTx and TVLTx. CONCLUSIONS: Both FSLTx and TVLTx offer the same prognosis in terms of patient and graft survival rates for children after a primary and elective liver transplantation. However, TVLTx has a higher morbidity.

Augmented procoagulant activity in cancer patients, treated with recombinant interferon-gamma in addition to recombinant tumor necrosis factor-alpha and melphalan.

Several investigators have reported that interferon-gamma (IFN gamma) can alter tumor necrosis factor alpha induced effects in vitro. We assessed in vivo effects of recombinant interferon-gamma (rIFN gamma) on recombinant tumor necrosis factor-alpha (rTNF alpha) induced activation of systemic blood coagulation in a non-randomized study in 20 consecutive cancer patients. Eight patients were treated with rIFN gamma prior to and during hyperthermic isolated limb perfusion with rTNF alpha and melphalan (IFN gamma group). They were compared with twelve patients who did not additionally receive rIFN gamma (non-IFN gamma group). Before start of perfusion, higher levels of TNF alpha, F1+2 and TAT levels were found in the IFN gamma group. Fibrinogen and ATIII levels tended to be lower in this group. High TNF alpha levels, due to leakage during perfusion, were associated with activation of coagulation in all patients, that became obvious after the end of perfusion, when heparin treatment had been antagonized. Activation, measured by increased F1+2 and TAT levels, was significantly stronger in the IFN gamma group. Monocytic TF remained low, possibly due to shedding of TF positive vesicles and/or sequestration of TF positive activated monocytes against the vessel wall. In both groups F1+2 and TAT levels declined 24 h after the perfusion, whereas monocytic TF increased to levels that were higher in the IFN gamma group. In conclusion, our data confirm a strong activation of coagulation induced by rTNF alpha in cancer patients. They suggest that rIFN gamma may lead to a slight activation of coagulation and augments TNF alpha induced procoagulant activity. These effects may be due to rIFN gamma induced sustained monocytic TF activity.

Angiosarcoma of the heart presenting as pulmonary disease.

A 23-year-old man died from the pulmonary manifestations of cardiac angiosarcoma. The absence of all cardiac signs and symptoms was an unusual feature. The clinical outcome was rapidly fatal. Apparently, the presence of cardiac symptoms in a patient with primary cardiac angiosarcoma is not obligatory.

Changes in portal hemodynamics and acute rejection in the first 2 weeks after orthotopic liver transplantation. A prospective Doppler ultrasound study.

RATIONALE AND OBJECTIVES: To analyze changes in Doppler ultrasound variables of the portal vein in relation to liver biopsy findings, the authors performed a prospective study of 316 Doppler ultrasound examinations in the first 2 weeks after orthotopic liver transplantation on 23 patients. METHODS: Recordings were obtained daily from the portal vein (diameter, maximum velocity, and flow). Correlations were explored between the Doppler ultrasound findings and histologic data. The chi-square test was used to analyze differences in Doppler ultrasound variables in patients with and without acute rejection. RESULTS: In our series of 23 patients, acute rejection was diagnosed by liver biopsy in nine of them (39%). Changes in portal vein diameter, maximum velocity, and flow did not correlate consistently with liver biopsy findings, due to a multifactorial origin. Changes in portal hemodynamics were observed in patients with hepatic artery thrombosis, portal vein stenosis, acute rejection, and sepsis. CONCLUSIONS: Although routine screening using Doppler ultrasound proved to be useful for the determination of rapid changes in portal hemodynamics within a short time, serial Doppler ultrasound examinations were not helpful in predicting acute rejection.

Doppler ultrasound of the hepatic artery and vein performed daily in the first two weeks after orthotopic liver transplantation. Useful for the diagnosis of acute rejection?

RATIONALE AND OBJECTIVES: To analyze changes in Doppler ultrasound variables in relation to liver biopsy findings for the diagnosis of acute rejection after orthotopic liver transplantation (OLT), the authors performed in a prospective study 316 Doppler ultrasound examinations in the first 2 weeks after OLT on 23 patients. METHODS: Recordings were obtained daily from the hepatic artery (resistive index [RI]) and hepatic vein (damping index [DI]). Correlations were explored between the Doppler ultrasound findings and histologic data. The chi-square test was used to analyze differences in Doppler ultrasound variables in patients with and without acute rejection. RESULTS: Serial Doppler ultrasound examinations showed a significant increase in the RI in 11 of 22 patients (50%); the 23rd patient was excluded because of hepatic artery thrombosis. Despite an agreement in 15 of 22 patients (68%) no statistically significant correlation could be found (positive predictive value 6/11 = 55%; negative predictive value 9/11 = 82%; chi-square = 3.14; P > 0.05). A significant increase in the DI was observed in 14 of 23 patients (61%). However, no statistically significant correlation could be found as well with this parameter (positive predictive value 6/14 = 43%; negative predictive value 6/9 = 67%; chi-square = 0.00; P > 0.05). CONCLUSION: Serial Doppler ultrasound examinations were not helpful in predicting acute rejection.

Preventing central venous catheter-related infection in a surgical intensive-care unit.

The cumulative effect of five measures (introduction of hand disinfection with alcohol, a new type of dressing, a one-bag system for parenteral nutrition, a new intravenous connection device, and surveillance by an infection control practitioner) on central venous catheter colonization and bacteremia was studied. Colonization was significantly reduced (P<.025); the decrease in bacteremia was not statistically significant.

The influence of hyperthyroidism on pharmacologically induced contractions of isolated resistance arteries.

We investigated the effect of hyperthyroidism on the responses of small mesenteric resistance arteries to several contractile and dilator agents. Hyperthyroidism was established by feeding rats for 28 days with 5 mg/kg L-thyroxine-containing rat chow. This treatment produced a stable hyperthyroid state, as indicated by the increased serum T4 levels (236 +/- 7 vs. 60 +/- 2; T4-treated vs. control). Preparations of small mesenteric arteries were mounted in an isometric wire myograph. Subsequently, concentration-effect curves were determined for K+, Ca2+, methoxamine, phenylephrine, 5-hydroxytryptamine (5-HT), 9,11-dideoxy-11 alpha, 9 alpha-epoxymethano-prostaglandin F2 alpha (U46619), methacholine and nitroprusside. Our results indicate that hyperthyroidism does not induce major changes in the sensitivity of isolated resistance vessels to K+, Ca+, the alpha-adrenoceptor agonist, methacholine and nitroprusside. Furthermore, neither the affinity of alpha-receptors for methoxamine, nor the alpha-receptor reserve was influenced by the hyperthyroid state of the animal. A clearly sensitizing influence of hyperthyroidism was found for the vasoconstrictor effects of both 5-HT (6.57 +/- 0.04 vs. 6.29 +/- 0.06; hyperthyroid vs. control) and the thromboxane A2 receptor agonist U46619 (6.78 +/- 0.13 vs. 6.30 +/- 0.09; hyperthyroid vs. control). Sensitization to both 5-HT and U46619 was abolished in the presence of N omega-nitro-L-arginine methylester HCl (L-NAME, 0.1 mM). 5-HT-induced contractions in vessels from hyperthyroid rats were diminished by prior incubation with indomethacin (10 microM). The present results indicate that during hyperthyroidism resistance vessels are sensitized to both 5-HT and U46619. This sensitization involves the nitric oxide/L-arginine pathway and probably also certain steps in the cyclooxygenase pathway.

Skin lesions due to exposure to methyl bromide.

Six patients were occupationally exposed to high concentrations of methyl bromide during a fumigation procedure using adequate airway protection. Within a few hours all patients developed skin lesions, consisting of sharply demarcated erythema with multiple vesicles and large bullae. There was a striking predisposition for parts of the skin that were relatively moist or subject to mechanical pressure, such as axillae, groin, and abdomen. Microscopically, early skin lesions revealed necrosis of keratinocytes, severe edema of the upper dermis, subepidermal blistering, and diffuse infiltration of neutrophils and, to a lesser degree, eosinophils. Two patients developed an urticarial rash approximately one week after the exposure. On histologic examination, these late lesions showed combined features of a spongiotic dermatitis and urticaria. No immunopathologic manifestations were observed. In all patients, the skin returned to normal after four weeks, except for some residual hyperpigmentation. Plasma bromide levels after exposure strongly suggested percutaneous absorption of methyl bromide.

Characterization of extracellular GABA in the substantia nigra reticulata by means of brain microdialysis.

Brain microdialysis was used to characterize extracellular gamma-aminobutyric acid (GABA) in the substantia nigra reticulata (SNR) of freely moving rats. The extracellular GABA in the SNR was characterized using acutely implanted probes (4-8 h after surgery; day 1) and chronically implanted probes (24 h after surgery; day 2). 3-Mercaptopropionic acid, a glutamic acid decarboxylase inhibitor, was used to identify GABA. This drug induced an immediate decrease in the extracellular GABA levels to 40% of basal values, suggesting that the detected GABA is, at least in part, newly synthesized. The basal levels of extracellular GABA measured either on day 1 or day 2 were not affected by infusion of micromolar amounts of tetrodotoxin. Therefore, a direct coupling between GABA dialysate concentrations and nerve-impulse flow does not seem to exist. Infusion of the GABA uptake inhibitor nipecotic acid (0.5 mmol/l) resulted in a 4-fold increase in the dialysate levels of GABA lasting at least for 3 h on both days. K+ stimulation (60 mmol/l) increased extracellular GABA levels in the SNR to 450% of basal values. This effect again did not differ significantly on day 1 and day 2. The origin of the extracellular GABA in the SNR, as recorded by microdialysis under the two experimental conditions, is discussed.

The influence of hyperthyroidism on beta-adrenoceptor-mediated relaxation of isolated small mesenteric arteries.

We investigated the influence of hyperthyroidism on relaxant responses of small mesenteric resistance arteries to beta-adrenoceptor agonists and to compounds stimulating the corresponding second-messenger system. Hyperthyroidism was induced by feeding rats for 28 days with 5 mg/kg L-thyroxine (T4)-containing rat chow. This treatment produced a stable hyperthyroid state, as indicated by several biochemical/metabolic and haemodynamic parameters. Preparations of small mesenteric arteries were mounted in an isometric wire myograph. Subsequently, concentration-effect curves were determined for isoproterenol, noradrenaline and salbutamol as well as for forskolin, dibutyryl-cAMP and theophylline. We also determined concentration-effect curves to the beta-adrenoceptor agonists in the presence of ICI 118,551 and CGP 20712A (i.e., in the presence of a selective beta 2- and beta 1-adrenoceptor antagonist, respectively). Apparent pA2-values were calculated to determine which beta-adrenoceptor subtype causes vasodilation. These experiments indicate that beta-adrenoceptor-mediated vasodilation involves both beta 1- and beta 2-adrenoceptors in mesenteric resistance vessels of both hyperthyroid and control rats. In our experiments hyperthyroidism has a sensitizing influence on vascular responses induced by the beta-adrenoceptor agonist isoproterenol and the selective beta 2-adrenoceptor agonist salbutamol. Sensitization to isoproterenol was abolished in the presence of ICI 118,551, whereas it was emphasized in the presence of CGP 20712A. Although this was not fully supported by the results obtained with noradrenaline, these results indicate that the sensitization to beta-adrenoceptor agonists is probably limited to the beta 2-adrenoceptor/G-protein complex and not associated with alterations of the corresponding second messenger system.

Thyroid hormone modulates inotropic responses, alpha-adrenoceptor density and catecholamine concentrations in the rat heart.

We investigated the influence of hyper- and hypothyroidism on basal parameters of isolated perfused hearts of rats. In addition the effects of different extracellular calcium concentrations ([Ca2+]o), the calcium entry promoter Bay K8644 and the alpha 1-adrenoceptor agonist methoxamine were investigated. Since alterations in alpha-adrenoceptor density could explain the increased sensitivity to methoxamine in hearts from hypothyroid rats, alpha 1-adrenoceptor density in the left ventricle was also established. Different time-schedules of exposure to hyper- and hypothyroidism were used to investigate whether the influence of chronic dysthyroid states on alpha 1-adrenoceptor density is transient and time-dependent. Simultaneously myocardial noradrenaline and adrenaline tissue concentrations were determined, since they might correlate with the observed changes. Hyperthyroidism was induced by feeding rats for 1, 4 and 8 weeks with 5 mg/kg L-thyroxine (T4)-containing rat chow. Hypothyroid rats were obtained by adding 0.05% propylthiouracil (PTU) to the drinking water during 1, 4 and 8 weeks. For the functional experiments animals were treated during 4 weeks, to mimic the clinical situation of a chronic endocrine disease. Langendorff hearts from hyperthyroid hearts showed an increased maximally developed relaxation velocity, whereas Langendorff hearts from hypothyroid rats showed an increased left ventricular pressure (LVP). We observed an increased maximal inotropic response to [Ca2+]o in hearts from both hyperthyroid and hypothyroid rats, indicating that both dysthyroid states interfere with the handling of calcium ions by the contractile apparatus. Unchanged responses to Bay K8644 in hearts from hyperthyroid and depressed responses in hearts from hypothyroid rats suggest that the involvement of L-type calcium channels is rather unlikely. Furthermore, the reflex increase in coronary flow in response to enhanced contractile force appeared to fail in hearts from hypothyroid rats. Sensitivity of the response to methoxamine was increased in hearts from hypothyroid rats, which was accompanied by a decrease in the number of myocardial alpha 1-adrenoceptors. Both T4 and PTU treatment resulted in a non-transient decrease of alpha 1-adrenoceptor density in left ventricular tissue. Furthermore, hypothyroidism increased the percentage of alpha 1A-binding sites, whereas in hyperthyroidism the distribution of the alpha 1-adrenoceptor subtypes was not affected. Myocardial tissue concentrations of noradrenaline and adrenaline were unchanged in hyperthyroid rats and decreased in hypothyroid rats. The present study indicates that thyroid hormones have a direct rather than a sympathetically mediated effect on alpha 1-adrenoceptor mediated myocardial functions.