Visual interpretation, not SUV ratios, is the ideal method to interpret 18F-DOPA PET scans to aid in the cure of patients with focal congenital hyperinsulinism

INTRODUCTION

Congenital hyperinsulinism is characterized by abnormal regulation of insulin secretion from the pancreas causing profound hypoketotic hypoglycemia and is the leading cause of persistent hypoglycemia in infants and children. The main objective of this study is to highlight the different mechanisms to interpret the 18F-DOPA PET scans and how this can influence outcomes.

MATERIALS AND METHODS

After 18F-Fluoro-L-DOPA was injected intravenously into 50 subjects' arm at a dose of 2.96-5.92 MBq/kg, three to four single-bed position PET scans were acquired at 20, 30, 40 and 50-minute post injection. The radiologist interpreted the scans for focal and diffuse hyperinsulinism using a visual interpretation method, as well as determining the Standard Uptake Value ratios with varying cut-offs.

RESULTS

Visual interpretation had the combination of the best sensitivity and positive prediction values.

CONCLUSIONS

In patients with focal disease, SUV ratios are not as accurate in identifying the focal lesion as visual inspection, and cases of focal disease may be missed by those relying on SUV ratios, thereby denying the patients a chance of cure. We recommend treating patients with diazoxide-resistant hyperinsulinism in centers with dedicated multidisciplinary team comprising of at least a pediatric endocrinologist with a special interest in hyperinsulinism, a radiologist experienced in interpretation of 18F-Fluoro-L-DOPA PET/CT scans, a histopathologist with experience in frozen section analysis of the pancreas and a pancreatic surgeon experienced in partial pancreatectomies in patients with hyperinsulinism.

Covariance statistics and network analysis of brain PET imaging studies

The analysis of structural and functional neuroimaging data using graph theory has increasingly become a popular approach for visualising and understanding anatomical and functional relationships between different cerebral areas. In this work we applied a network-based approach for brain PET studies using population-based covariance matrices, with the aim to explore topological tracer kinetic differences in cross-sectional investigations. Simulations, test-retest studies and applications to cross-sectional datasets from three different tracers ([18F]FDG, [18F]FDOPA and [11C]SB217045) and more than 400 PET scans were investigated to assess the applicability of the methodology in healthy controls and patients. A validation of statistics, including the assessment of false positive differences in parametric versus permutation testing, was also performed. Results showed good reproducibility and general applicability of the method within the range of experimental settings typical of PET neuroimaging studies, with permutation being the method of choice for the statistical analysis. The use of graph theory for the quantification of [18F]FDG brain PET covariance, including the definition of an entropy metric, proved to be particularly relevant for Alzheimer's disease, showing an association with the progression of the pathology. This study shows that covariance statistics can be applied to PET neuroimaging data to investigate the topological characteristics of the tracer kinetics and its related targets, although sensitivity to experimental variables, group inhomogeneities and image resolution need to be considered when the method is applied to cross-sectional studies.

False-positive findings on 6-[18F]fluor-l-3,4-dihydroxyphenylalanine PET (18F-FDOPA-PET) performed for imaging of neuroendocrine tumors

BACKGROUND/AIM

PET with 6-[18F]fluor-l-3,4-dihydroxyphenylalanine (¹⁸F-FDOPA) has been shown to be a useful imaging tool with a high sensitivity for the visualization of neuroendocrine tumors (NETs). ¹⁸F-FDOPA uptake in tumors other than NETs has been suggested previously, but data on this phenomenon are limited. We therefore studied the non-physiological, false-positive uptake of ¹⁸F-FDOPA in a large population of patients with a NET or with a high clinical suspicion of harboring a NET.

PATIENTS AND METHODS

Retrospective single-center study among adult patients in whom ¹⁸F-FDOPA PET scintigraphy was performed between January 2004 and December 2014. The original scan report was compared with the original pathology report corresponding with the ¹⁸F-FDOPA PET-positive lesion. In case this was inconsistent with the diagnosis of a NET, both the scan and the pathology slides were reassessed. Specimens of these non-NET tissues were immunohistochemically stained for AADC.

RESULTS

1070 ¹⁸F-FDOPA PET scans from 705 patients were evaluated. Focal or multiple ¹⁸F-FDOPA-avid lesions were described in 709 ¹⁸F-FDOPA PET scans (66%). Histology of these ¹⁸F-FDOPA PET-positive lesions was present in 508 (72%) cases. In seven cases, the histopathology was not compatible with NET but showed squamous cell carcinoma of the cervix, multiple myeloma (two cases), hepatocellular carcinoma, Schwannoma, adrenocortical carcinoma and a skeletal myxoid chondrosarcoma, with positive immunohistochemical staining for AADC in 67%.

CONCLUSIONS

Pathological uptake of ¹⁸F-FDOPA does not always indicate the presence of a NET. The possibility of ¹⁸F-FDOPA uptake by tumor types other than NETs, although rare, should be considered.

Accuracy of 18F-FDOPA Positron Emission Tomography and 18F-FET Positron Emission Tomography for Differentiating Radiation Necrosis from Brain Tumor Recurrence

BACKGROUND

Distinguishing radiation necrosis from brain tumor recurrence remains challenging. We performed a meta-analysis to assess the diagnostic accuracy of 2 different amino acid tracers used in positron emission tomography/computed tomography scans: ¹⁸F-FDOPA (6-[18F]-fluoro-L-3,4-dihydroxyphenylalanine) and ¹⁸F-FET (O-(2-18F-fluoroethyl)-L-tyrosine).

METHODS

We searched for studies in 3 databases: PubMed, Embase, and Chinese Biomedical databases. The data were extracted from eligible studies and then processed with heterogeneity test, threshold effect test, and calculations of sensitivity, specificity, and area under the summary receiver operating characteristic curve. Meta-regression and subgroup analyses were performed to explore the source of heterogeneity.

RESULTS

A total of 48 studies (¹⁸F-FDOPA, n = 21; ¹⁸F-FET, n = 27) were included. Quantitative synthesis determined pooled weight values in the ¹⁸F-FDOPA and ¹⁸F-FET groups: sensitivity, 0.85 versus 0.82; specificity, 0.77 versus 0.80; diagnostic odds ratio, 21.7 versus 23.03; area under the curve (AUC) values, 0.8771 versus 0.8976 (P = 0.46). Moreover, the type of tumor was identified as the possible source of the significant heterogeneity (I² = 52%; P = 0.003) found in the ¹⁸F-FDOPA group. In meta-regression and subgroup analyses, ¹⁸F-FDOPA showed better diagnostic accuracy in patients with glioma compared with patients with brain metastases (AUC values, 0.9691 vs. 0.837; P < 0.01). ¹⁸F-FDOPA also showed a significant advantage in the diagnosis of glioma recurrence compared with ¹⁸F-FET (AUC values, 0.9691 vs. 0.9124; P = 0.015).

CONCLUSIONS

Both ¹⁸F-FDOPA and ¹⁸F-FET exhibit moderate overall accuracy in diagnosing brain tumor recurrence from radiation necrosis. However, ¹⁸F-FDOPA is more adept at diagnosing glioma recurrence compared with brain metastases, and it is more effective than ¹⁸F-FET in diagnosing glioma recurrence.

Urinary 8-hydroxydeoxyguanosine levels as a biomarker for progression of Parkinson disease

8-hydroxydeoxyguanosine (8-OHdG) has been used to evaluate oxidative stress. The authors investigated urinary 8-OHdG levels in 72 patients with Parkinson disease (PD) and in normal and disease control groups. The mean urinary 8-OHdG increased with the stage of PD and was not influenced by the current dose of DOPA. Our results suggest that urinary 8-OHdG is a potentially useful biomarker for evaluating the progression of PD.

6-pyruvoyl tetrahydropterin synthase deficiency: a case report

A 5 day old girl screened positive for hyperphenylalaninemia on routine newborn screening. Initial diagnostic work-up showed elevated blood phenylalanine of 1100 mmol/L and low tyrosine. Limited protein diet and phenylalanine-free formula were prescribed. Further investigation revealed a defect in biopterin metabolism. Urine had no detectable biopterin (BH4) and an elevated level of neopterin at 24.31 mmol/mole Cr. Enzymatic assay showed zero level of 6-pyruvoyl tetrahydropterin synthase. The activity in the mother was 3.5 or 19.9% of controls consistent with heterozygosity. The concentrations of 5-hydroxyindoleacetic acid and homovanillic acid in the cerebrospinal fluid were below the reference ranges. A treatment regimen of BH4 tablets, 5 hydroxytryptophan and DOPA was initiated. The diagnostic evaluation, management and follow-up of patients with this disorder will be outlined. This is the first reported case of a Filipino with a defect in biopterin metabolism.

Intrauterine growth restriction induces up-regulation of cerebral aromatic amino acid decarboxylase activity in newborn piglets: [18F]fluorodopa positron emission tomographis study

There is evidence that intrauterine growth restriction (IUGR) is associated with altered dopaminergic function in the immature brain. However, the relevant enzyme activities have not been measured in the living neonatal brain together with brain oxidative metabolism. Therefore, fluorine-18-labeled 6-fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) was used together with positron emission tomography to estimate the activity of the aromatic amino acid decarboxylase in the brain of 10 newborn IUGR piglets (2 to 5 d old; body weight, 908 +/- 109 g) and in 10 normal-weight (3 to 5 d old; body weight, 2142 +/- 373 g) newborn piglets. The regional transport of FDOPA to the brain and the clearance rate of labeled metabolites from brain tissue were broadly similar in the two groups. However, the regional rate constant for back flux from the brain was markedly increased in IUGR piglets for striatum (72%) and frontal cortex (83%) (p < 0.05). Furthermore, the rate constant for conversion of FDOPA to fluorodopamine was markedly increased (between 48% in cerebellum and 91% in mesencephalon, p < 0.05) in all brain regions of IUGR piglets studied. Thus, it is suggested that IUGR induces an up-regulation of aromatic amino acid decarboxylase activity that is not related to alterations in brain oxidative metabolism.

Dopaminergic denervation enhances susceptibility to hydroxyl radicals in rat neostriatum

To determine if greater amounts of hydroxyl radical (*OH) are formed by dopamine (DA) denervation and treatment with L-dihydroxyphenylalanine (L-DOPA), the neostriatum was DA denervated (99% reduction in DA content) by 6-hydroxydopamine treatment (134microg icv, desipramine pretreatment) of neonatal rats. At 10 weeks the peripherally restricted dopa decarboxylase inhibitor carbidopa (12.5mg/kg i.p.) was administered 30min before vehicle, L-DOPA (60mg/kg i.p.), or the known generator of reactive oxygen species, 6-hydroxydopa (6-OHDOPA) (60mg/kg i.p.); and this was followed 30min later (and 15 min before termination) by the spin trap, salicylic acid (8micromoles icv). By means of a high performance liquid chromatographic method with electrochemical detection, we found a 4-fold increase in the non-enzymatically formed spin trap product, 2,3-dihydroxybenzoic acid (2,3-DHBA), with neither L-DOPA nor 6-OHDOPA having an effect on 2,3-DHBA content of the neostriatum. Basal content of 2,5-DHBA, the enzymatically formed spin trap product, was 4-fold higher vs. 2,3-DHBA in the neostriatum of untreated rats, while L-DOPA and 6-OHDOPA each reduced formation of 2,5-DHBA. We conclude that DA innervation normally suppresses *OH formation, and that the antiparkinsonian drug L-DOPA has no effect (2,3-DHBA) or slightly reduces (2,5-DHBA) *OH formation in the neostriatum, probably by virtue of its bathing the system of newly formed *OH.

Gata3 loss leads to embryonic lethality due to noradrenaline deficiency of the sympathetic nervous system

Mouse embryos deficient in Gata3 die by 11 days post coitum (d.p.c.) from pathology of undetermined origin. We recently showed that Gata3-directed lacZ expression of a 625-kb Gata3 YAC transgene in mice mimics endogenous Gata3 expression, except in thymus and the sympathoadrenal system. As this transgene failed to overcome embryonic lethality (unpublished data and ref. 3) in Gata3-/- mice, we hypothesized that a neuroendocrine deficiency in the sympathetic nervous system (SNS) might cause embryonic lethality in these mutants. We find here that null mutation of Gata3 leads to reduced accumulation of Th (encoding tyrosine hydroxylase, Th) and Dbh (dopamine beta-hydroxylase, Dbh) mRNA, whereas several other SNS genes are unaffected. We show that Th and Dbh deficiencies lead to reduced noradrenaline in the SNS, and that noradrenaline deficiency is a proximal cause of death in mutants by feeding catechol intermediates to pregnant dams, thereby partially averting Gata3 mutation-induced lethality. These older, pharmacologically rescued mutants revealed abnormalities that previously could not be detected in untreated mutants. These late embryonic defects include renal hypoplasia and developmental defects in structures derived from cephalic neural crest cells. Thus we have shown that Gata3 has a role in the differentiation of multiple cell lineages during embryogenesis.

[Physico-chemical properties of borate derivatives of DOPA, dopamine, and their liposome forms]

To increase the solubility of L-3,4-dihydroxyphenylalanine (DOPA) and dopamine (DA) incorporated in liposomes, it was suggested to convert them into ammonium and 1-adamantylammonium borate complexes. The structure of these complexes was studied by 11B and 1H NMR, IR, and mass spectrometry and conductometry. The liposomic form of the complexes is characterized by a high active compound/lipid molar ratio (0.5). Catechols in the form of complex salts are retained better within the inner volume of liposomes.

A role of SH-compounds in maturation of melanosomes in cells cultured from nevus Ota

A role of SH-compounds such as cysteine and glutathione in melanogenesis in dermal melanocytes cultured from Ota's nevus tissue was demonstrated in relation to another substrate, dihydroxyphenylalanine (DOPA). Chemical analysis of eumelanin and pheomelanin was performed in addition to the conventional electron microscopic observation. Supplements of the culture medium with each of these compounds separately for two weeks gave rise to the formation of pre-pheomelanosomes and secondary lysosomes or myelinosome-like inclusions. When DOPA and glutathione were added to the medium together, the maturation of melanosomes was promoted. This was proven by the increase in electron-density of pre-melanosomes observed as well as by the content of pheomelanin and eumelanin. However, mature melanosomes were not formed when each of these chemicals was added to the medium individually for the same periods. The melanosome maturation seemed to occur via a process involving secondary lysosomes or myelinosomes, in which more electron-dense particles accumulated in the presence of both reagents. The pheomelanosomal process was also observed, but typical eumelanosome-related processes were not observed in this culture system.

The effect of unilateral neurotoxic lesions to serotonin fibres in the medial forebrain bundle on the metabolism of [3H]DOPA in the telencephalon of the living rat

We used quantitative autoradiography to measure the contribution of the 5-hydroxytryptamine (5-HT, serotonin) innervation of rat telencephalon to the synthesis of dopamine (DA) from exogenous L-DOPA. One week after stereotaxic infusions of 5,7-dihydroxy-tryptamine (5,7-DHT, 1.6 micrograms) into the right medial forebrain bundle (MFB), rats received [3H]DOPA (200 microCi,i.v.), which circulated for 90 min. The specific bindings in vitro of the 5-HT uptake site ligand [3H]citalopram and the DA uptake site ligand [125I]RTI-55 were measured in cryostat sections from the prosencephalon. In most structures ipsilateral to the lesion, [3H]citalopram specific binding was substantially reduced (50-90%). In the lateral habenula specific binding declined by only 30-40%, reflecting the presence of a 5-HT pathway deviating from the MFB at the mesencephalic flexure. [125I]RTI-55 binding in the basal ganglia was reduced by 50% on the side of the 5,7-DHT lesion, but was unperturbed in rats pretreated with desmethylimipramine (DMI). 5,7-DHT infusions decreased the synthesis of [3H]DA from [3H]DOPA in vivo in the basal ganglia by (40-90%). Pretreatment with DMI protected [3H]DA synthesis in the basal ganglia, but not in the olfactory tubercle and amygdala ipsilateral to the lesion. Whereas the 5-HT innervation does not contribute greatly to [3H]DA synthesis in the basal ganglia, a substantial proportion of [3H]DA synthesis in olfactory tubercle and amygdala requires an intact 5-HT innervation.

Metabolic fate of the sympathoneural imaging agent 6-[18F]fluorodopamine in humans

We examined the metabolism of 6-[18F]fluorodopamine, by assaying arterial plasma concentrations of radioactivity, 6-[18F]fluorodopamine, and 6-[18F]fluorodopamine metabolites in untreated subjects or subjects given desipramine to block neuronal uptake of catecholamines or tyramine to displace vesicular amines. After the 3-min 6-[18F]fluorodopamine infusion, plasma 6-[18F]fluorodopamine levels declined precipitously, total radioactivity declining slowly. After 30 min, the main identified metabolite was 6-[18F]fluorodopamine-sulfate. Desipramine attenuated the rapid increase in plasma 6-[18F]fluorodihydroxyphenylacetic acid levels, and tyramine briefly increased 6-[18F]fluorodopamine levels. Neither drug affected 6-[18F]fluorodopamine-sulfate levels. The results indicate that soon after 6-[18F]fluorodopamine infusion, plasma radioactivity corresponds mainly to 6-[18F]fluorodopamine metabolites; that sympathetic nerves rapidly remove 6-[18F]fluorodopamine, which then undergoes oxidative deamination in the neuronal cytoplasm and sequestration in sympathetic vesicles; and that sulfoconjugation of [18F]fluorodopamine occurs extraneuronally.

Bladder wall radiation dose in humans from fluorine-18-FDOPA

PET, in conjunction with 18F-fluorodopa (FDOPA), has become the standard technique to assess basal ganglia degeneration in patients with movement disorders. Based on published dosimetry data, the injected dose of FDOPA is limited to 111 Mbq (3 mCi) because of exposure to the bladder wall, which is the critical organ for such studies. These dosimetry studies are based on mathematical models for the bladder radioactivity accumulation and clearance when the subjects were asked to void approximately 2 hr after the intravenous injection of FDOPA. In this study, we improved the radiation dose estimate to the bladder wall using dynamic PET to image the bladder during the uptake phase as well as before and after voiding.

METHODS

The subjects were tested on a new protocol. They were hydrated preinjection and given a first bladder void break at 40 min postinjection and a second void at the end of study at 120 min.

RESULTS

The MIRD model, applied to the data collected from 10 adults of both sexes, yielded an average absorbed dose of 0.15 +/- 0.08 mGy/MBq (0.57 +/- 0.28 rad/mCi).

CONCLUSION

This absorbed dose is significantly lower than previous estimates and allows for FDOPA injections up to 333 Mbq (9 mCi).

[Physico-chemical properties of liposome forms of L-3,4-dihydroxyphenylalanine (DOPA) and dopamine]

L-3,4-Dihydroxyphenylalanine (DOPA) and dopamine encapsulated in liposomes have been obtained. These preparations can be used as drugs for Parkinson's disease. The level of encapsulation of the compounds under study in liposomes and their partition coefficients have been determined. The kinetics of DOPA (or dopamine) exit from the liposomes have been studied.

Quantification of dopamine metabolism in man: a mathematically justifiable approach

Model derivation, the proposal of the best model to fit the measured data, is a crucial and often neglected step in compartmental analysis. Since the model which best fits the data in a statistical sense may be simpler than the known physiology of the system, the order (mathematical complexity) of the model that can be accepted must be determined independently of physiological considerations. Although [18F]6-fluoro-L-dopa (F-dopa) has been used as a tracer for the investigation of presynaptic dopamine metabolism for a number of years, a definitive method of quantitative analysis has not yet emerged. Simple graphical analyses have been used predominantly in clinical studies, while compartmental analyses have been used to gain a better understanding of F-dopa kinetics. Over the years quantitative approaches to F-dopa metabolism have grown increasingly complicated, and complex models that rely on the use of parameter constraints, or simplifying assumptions in order to collapse the model to solvable dimensions, have been developed. We propose a simple compartmental model to quantify the metabolism of F-dopa in the striatum. Both compartmental and graphical analyses were performed using this model, and the mathematical expression which relates the results of the two analyses was derived. The ability of our approach to reveal and quantify differences in the dopaminergic metabolism of individuals has been demonstrated in a small number of studies.

Short-latency median nerve somatosensory evoked potentials in three cases of parkinsonism and dopa responsive dystonia

We studied somatosensory evoked potentials after median nerve stimulation in a sporadic case of dopa responsive dystonia and in two brothers with different combinations of dystonia and parkinsonism. The latencies of all potentials were normal. The amplitude of the P20-N30 frontal complex showed a significant reduction in all cases. Our results suggest a common neurophysiopathological pattern underlying these two conditions.

Intrarenal production of dopamine and natriuresis following DOPA and saline infusions in healthy human volunteers

The interactions of intrarenal dopamine (DA) synthesis and natriuresis were studied in 11 healthy volunteers by giving a low and high sodium diet (LoSo, 50 mmol Na+; HiSo, 250 mmol Na+). On 2 days in both dietary phases an acute saline load was given, without or with an infusion of the DA precursor 3, 4-dihydroxyphenylalanine (DOPA) 0.15 microgram kg-1 min-1. Urinary excretion rates of sodium (UNa V), DOPA (UDOPA V), DA (UDA V) and noradrenaline (NA; UNA V), hormonal parameters, blood pressure (BP), glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured. On HiSo UDOPA V increased by 35% (P < 0.05) while UDA V remained unchanged. Only weak correlations were found between 24h UNa V and UDA V (r = 0.23) or UDOPA V (r = 0.39). On both diets and without the DOPA infusions, the saline infusions enhanced UNa V but did not increase UDA V. The DOPA infusions caused no significant change of UNa V, in spite of five- to eight-fold increases in UDA V. During LoSo the DOPA infusion only caused a slightly larger increase of UNa V after the saline infusion, when expressed as percentage change to the pre-saline UNa V (119 +/- 25% without DOPA infusion, 244 +/- 56%, P < 0.05 with DOPA infusion). On HiSo the DOPA infusion did not affect UNA V. The dietary sodium intake and the DOPA infusions did not influenced BP, GFR, or ERPF. In conclusion, dietary sodium intake or acute sodium loads did not clearly modulate UDA V.(ABSTRACT TRUNCATED AT 250 WORDS)

Beneficial effects of co-administration of catechol-O-methyltransferase inhibitors and L-dihydroxyphenylalanine in rat models of depression

The administration of catechol-O-methyltransferase inhibitors alone changed neither the behavior of the rats in two animal models of depression, the forced swimming test (entacapone and tolcapone) or in the learned helplessness paradigm (tolcapone), nor the locomotor activity. L-Dihydroxyphenylalanine (L-DOPA) and carbidopa treatment as such decreased motility but did not improve the behavior in the antidepressant tests. Co-administration of catechol-O-methyltransferase inhibitors and L-DOPA/carbidopa increased the performance of rats in both tests without increasing locomotor activity. Catechol-O-methyltransferase inhibitors could be beneficial as adjunct drugs of L-DOPA not only in Parkinson's disease but also in the coincident depressive illness.

Apomorphine SC treatment in parkinsonian patients with long-term L-dopa syndrome during L-dopa drug holiday

The Long-Term Dopa Syndrome (LTDS) is one of the main problems in the management of advanced parkinsonian patients. A transient L-Dopa withdrawal (Drug Holiday, DH) can be useful to improve the drug response after DH, even if this approach presents risks due to patient akinesia. We tried to verify if Apomorphine sc administration during DH (DH with Apomorphine, DHA) can: a) reduce the risks connected with DH: b) maintain the benefits of DH: c) standardize the duration of DH. Twenty-five parkinsonian patients with LTDS were treated with Apomorphine sc during DH (14 days). No patient had any severe side effects. The follow-up at 180 days, conducted using the Unified Parkinson's Disease Rating Scale, demonstrated a significant improvement in the clinical conditions of about 70% of the patients, allowing a 27.1% reduction in daily L-dopa dosage. DHA can represent a valid therapeutical approach for parkinsonian patients with LTDS.

Effects of long-term infusions of dopa and carbidopa on renin and steroid secretion in the rat

Plasma, kidney, and adrenal catecholamine concentrations were varied by infusing rats with L-dopa and/or carbidopa for 2 weeks. L-Dopa infusion (300 micrograms/day) increased dopamine concentrations in plasma, adrenal zona glomerulosa, and kidney by 140%, 74%, and 224%, respectively: the dopamine content of the adrenal inner cortex plus medulla was not increased. Infusion of carbidopa alone had no detectable effect upon endogenous dopamine concentrations. Concomitant infusion (300 micrograms/day) of carbidopa with L-dopa blocked the rise in plasma and adrenocortical dopamine caused by L-dopa alone. Plasma aldosterone and plasma and kidney active renin concentrations were unaffected by L-dopa administration but plasma corticosterone and deoxycorticosterone (DOC) were significantly elevated (P < 0.05); increases in DOC appeared greater than those of corticosterone. These data cast doubt on the theory that dopamine is a physiological tonic inhibitor of aldosterone synthesis in rats. However, in the rat, stimulatory effects of L-dopa on plasma concentrations of precursors of aldosterone might be of physiological significance since DOC is a potent mineralocorticoid.

[Duration of second remission of Hodgkin's disease in children. Results of treatment achieved by the Polish Leukemia and Malignant Lymphoma Therapy in Children Group]

Recurrence was noted in 18.5% of 194 children, in which chemotherapy with MVPP regimen produced complete I remission. In 6 out of 36 children with recurrent disease MVPP regimen was repeated, while the remaining children were treated with B-DOPA alone or combined with MOPP regimen. Local radiotherapy was used in 17 children. The second complete remission was achieved in 30 (83.7%) children. Thirteen out of 36 patients died because of the progress of the disease (11 children), and for complications (2 children). Percentage of persisting 5- and 10-year II remissions are 58.2% and 54.6%, respectively. A 5- and 10-year survival rates in children with recurrent disease are 80.5% and 60.5%, respectively. Our relatively favourable results we associate--first of all--with the chemotherapy intensity.

Disposition of gamma-glutamyl levodopa (gludopa) after intravenous bolus injection in healthy volunteers

1. The pharmacokinetics of gludopa in healthy volunteers were studied at two doses, 250 micrograms kg-1 and 100 micrograms kg-1, after rapid intravenous bolus injection. 2. Gludopa had a clearance of 4.43 +/- 1.50 ml min-1 kg-1 and 4.92 ml min-1 kg-1 at the higher and lower doses, respectively. Corresponding half-lives were 29.2 +/- 3.7 min and 32.5 +/- 5.6 min, and volumes of distribution were 0.183 +/- 0.052 l kg-1 and 0.235 +/- 0.07/ l kg-1. 3. Urinary excretion of dopamine rose sharply after injection of gludopa at both doses, peaking at 30 min. At this time, amounts were over 215 and 60 times baseline values at the higher and lower dose of gludopa, respectively. Urinary dopamine rose in parallel with urinary levodopa excretion, supporting the view that levodopa is the precursor of urinary dopamine. 4. Less than 1% of the injected dose of gludopa was excreted unchanged in the urine. 5. These findings suggest that, in man, gludopa is an efficient pro-drug for dopamine. Gludopa may find therapeutic use in conditions where the beneficial renal effects of dopamine may be indicated.

Five years' experience with gamma-L-glutamyl-L-dopa: a relatively renally specific dopaminergic prodrug in man

1. Over the last 5 years we have given intravenous gludopa in man and established its effects on the kidney. 2. At doses of 12.5 to 100 micrograms kg-1 min-1 it is natriuretic and also tends to increase renal blood flow and glomerular filtration. Despite the natriuresis, plasma renin activity is depressed and this effect is blocked by domperidone. The receptors for the tubular natriuretic effect are blocked by d-sulpiride. 3. Four-hour infusions in man do not lower blood pressure; 10-h infusions lower blood pressure and increase pulse rate. 4. The oral bioavailability of gludopa is only 1 to 2% and this rules out the dipeptide as an effective dopaminergic prodrug.

Effect of prolonged intravenous infusion of gludopa in humans and a preliminary study of its oral bioavailability

Intravenous infusion of gamma-glutamyl-L-dopa (25 micrograms/kg/min) for 10 h in normal humans caused a natriuresis of 46.5 mmol of sodium without an increase in plasma renin activity and was associated with small but significant falls in blood pressure. In a second study the oral bioavailability of gludopa was estimated in normal subjects and found to be low (less than 2%). The increase in urine dopamine excretion and the natriuretic effect of gludopa were much larger after intravenous infusion than oral dosing.

Derivation of urinary dopamine from plasma dopa

1. We estimated the extent to which circulating dopa (3,4-dihydroxyphenylalanine) is the source of urinary dopamine (DA; 3,4-dihydroxyphenethylamine). Tritiated dopa ([3H]dopa) was infused for 90 min into the left renal artery of seven anaesthetized foxhounds, and levels of labelled and unlabelled dopa and DA were measured in the ureteral urine and in the femoral arterial and left renal venous plasma. 2. Only a small percentage of [3H]dopa delivered to the kidneys was excreted as [3H]DA (0.59% from the left kidney, 0.68% from the right); however, the arterial concentration of endogenous dopa (1220 pg/ml) and the renal plasma flows (144 and 141 ml/min by p-aminohippurate clearances) were such that all of the urinary excretion of endogenous DA (about 1 ng/min from each kidney) could be accounted for by uptake and decarboxylation of circulating endogenous dopa. 3. Plasma dopa is the main source of urinary DA.

Inhibition of decarboxylase and levels of dopa and 3-O-methyldopa: a comparative study of benserazide versus carbidopa in rodents and of Madopar standard versus Madopar HBS in volunteers

The combinations of benserazide and levodopa (1:4, Madopar) and of carbidopa and levodopa (1:10 and 1:4, Sinemet) are currently the most effective treatment of Parkinson's disease. In the present comparative study some effects of the peripheral aromatic L-amino acid decarboxylase (AADC) inhibitors benserazide and carbidopa administered alone or in combination with levodopa by the oral route were investigated in two animal species (rat and mouse) and in healthy volunteers. Benserazide is about 10 times more potent than carbidopa as inhibitor of peripheral AADC both in animals and man. Even at relatively high doses (up to 60 mumol/kg p.o.) benserazide is shown in animals to inhibit the decarboxylation of levodopa only in the extracerebral tissues, thus permitting the formation of dopamine in the striatum and in the hypothalamus. As benserazide is the most potent peripheral AADC inhibitor presently available, is well tolerated and relatively nontoxic even when used chronically, it appears to be the peripheral AADC inhibitor of choice for the development of controlled-release formulations in which Dopa is combined with a peripheral AADC inhibitor. When administered to healthy subjects the pharmacokinetics of the new drug delivery system named Madopar HBS (hydrodynamically balanced system) was characterized by lower and delayed plasma peak concentrations but a longer-lasting concentration of Dopa than after Madopar standard. Therefore, this new controlled-release system may reduce the clinical fluctuations occurring in patients with 'wearing-off' and 'on-off' phenomena.

Domperidone treatment in man inhibits the fall in plasma renin activity induced by intravenous gamma-L-glutamyl-L-dopa

The dopamine pro-drug gamma-L-glutamyl-L-dopa (gludopa) was administered intravenously to six normal subjects at a dose of 12.5 micrograms min-1 kg-1, either with or without the dopamine antagonist domperidone. A control was provided by the intravenous infusion of domperidone and saline on a separate occasion. Intravenous gludopa produced a significant natriuresis, whether administered alone or in combination with domperidone. After gludopa infusion, there was a significant fall in plasma renin activity, an effect which was attenuated significantly by concomitant treatment with domperidone. These observations suggest that blockade of renal DA2 dopamine receptors has little or no effect on gludopa-induced natriuresis, but that at least part of the dopaminergic inhibition of renin release is mediated by renal DA2 receptors.

gamma-L-Glutamyl-L-dopa is a dopamine pro-drug, relatively specific for the kidney in normal subjects

gamma-L-Glutamyl-L-dopa was given by intravenous infusion to eight normal subjects at doses of 12.5 and 100 micrograms min-1 kg-1. Both doses of the dipeptide resulted in an increase in mean urinary sodium excretion. Mean effective renal plasma flow rose at both doses, but mean glomerular filtration rate increased only at the lower dose. There was a fall in mean plasma renin activity after the infusion of both 12.5 and 100 micrograms min-1 kg-1. Mean urine free dopamine excretion increased by 280- and 2500-fold at infusion rates of 12.5 and 100 micrograms min-1 kg-1 respectively. Mean plasma free dopamine rose at both doses but the increase at 12.5 micrograms min-1 kg-1 was not to a level previously associated with systemic effects of the catecholamine. On administration of the dipeptide at 12.5 micrograms min-1 kg-1 there were no changes in blood pressure or heart rate, but at the higher dose there was a fall in diastolic blood pressure. At a dose of 12.5 micrograms min-1 kg-1 in man, there is kidney specific conversion of gludopa to dopamine.

Plasma dopamine: regulation and significance

Dopamine (DA) normally circulates in plasma. The plasma concentration of the free form of DA is approximately equivalent to that of epinephrine (E) and 20% that of norepinephrine (NE). The free form constitutes less than 2% of total plasma DA, and the remainder exists predominantly as sulfate or glucuronide conjugates. DA is found in adrenal medulla and cortex, peripheral nerves, sympathetic ganglia, carotid body, and kidney, but quantitatively the origin of circulating DA remains poorly understood. Plasma concentrations of free DA increase in association with events that increase sympathetic tone, although to a much lesser degree than seen for NE or E. Thus, upright posture, bicycle exercise, a variety of emotional and physical stresses, and hypoglycemia may be associated with increases in plasma free DA. Plasma DA decreases during the course of dietary sodium depletion in humans, in contrast to the plasma NE response, and consistent with a physiological role for DA in the regulation of aldosterone secretion. Plasma DA increases after administration of its precursor L-dihydroxyphenylalanine, together with the decarboxylase inhibitor carbidopa. Plasma NE and (in some studies) plasma DA decrease after administration of the DA receptor agonist bromocriptine. In contrast, plasma DA and one of its major metabolites, homovanillic acid, increase after administration of the DA receptor antagonist haloperidol. Administration of the endogenous opioid peptide beta-endorphin into the brain increases central sympathetic outflow, thus increasing plasma DA concentration, although to a lesser extent than for NE or E. Disordered basal concentrations of DA in plasma or disordered responses of plasma DA have been reported in a number of disease states. Clear understanding of physiological roles of DA in plasma and of its pathophysiology awaits definition.

[Senile Parkinsonism: its motor and psychological defects]

25% of patients with Parkinson's disease demonstrate the first symptoms with 70 years. The deficiency of Tyrosinhydroxylase is the trigger of the decreased level of Dopamin in the basal ganglia. The implications are the typical symptoms (tremor, rigor and akinesia) and the psychopathological decompensations as depression, delirs and bradyphrenie.

Effect of DOPA-loading on glutathione-dependent 5-S-cysteinyldopa genesis in melanoma cells in vitro

The effect of dopa, cysteine, and glutathione on 5-S-cysteinyldopa (5-S-CD) genesis in melanoma cells cultured in normal and tyrosine- and cysteine-free media has been studied. In normal media only melanotic melanoma cells have been found to secrete 5-S-CD into the medium. In the presence of dopa and cysteine, both, media incubated with and without cells have been found to produce 5-S-CD. In the presence of dopa and glutathione, however, cell-free media did not show the presence of 5-S-CD. In contrast melanoma cell-cultured media has been found to contain large quantities of this amino acid. The optimum condition for maximum production of 5-S-CD via glutathione-dependent pathway has been found to be at the dopa concentration of 10(-5) M when glutathione is present at the concentration of 10(-5) M in the culture medium. Thus dopa concentration with regards to glutathione is 1:1 on the molar basis which is twice the dopa concentration required in in vitro noncellular tyrosinase system. It is suggested that higher dopa requirement in our melanoma cell culture system reflects the co-existence of eu- and pheomelanin synthesis taking place according to their genetically predetermined proportions.

[Bromocriptin in the treatment of progressive stages of Parkinson's disease (author's transl)]

Forty patients with severe Parkinson's disease (23 men, 17 women) who had been treated for six years with L-dopa-decarboxylase inhibitor, were part of a placebo-controlled double-blind trial to test the effectiveness of bromocriptin. In all patients the effectiveness of L-dopa had been decreasing, 34 patients had L-dopa-induced dyskinesias, 35 "on-off" symptoms. Bromocriptin dosage was gradually increased to a total dose of 30 - 40 mg daily. This led to a 25% reduction in L-dopa requirements. The symptoms of Parkinson's disease were favourably influenced, with rigor, tremor and also walking disturbances responding better than bradykinesia of the hands. At the same time, there was a marked prolongation of the periods of good mobility ("on" time) from 7 to 10.8 hours without influence on other "on-off" symptoms such as paradoxical akinesia. Two patients had to be excluded from the trial because the treatment caused side effects (orthostatic hypotension, exogenous psychotic symptoms). Other side effects, such as nausea and mild forms of collapse, could be controlled by drugs.

[Comparative evaluation of the effect of haloperidol and clozapine on rotational movements induced by caudate nucleus stimulation in cats]

Chronic experiments on cats were carried out to study the effect of haloperidol and clozapine on the pattern of contralateral rotations produced by electric stimulation of the caudate nucleus. Haloperidol (0.125 mg/kg) facilitated the appearance of the reactions during stimulation of the lateral parts of the nucleus while clozapine selectively decreased the thresholds of the "manage" movements in the course of stimulating but the medial zones of the structure. Unlike haloperidol, clozapine (2.5 mg/kg) eliminated the forced reactions of the tonic type originating from the lateral parts of the caudate nucleus. Haloperidol (0.125 mg/kg) suppressed the stereotyped behavior caused by DOPA (100 mg/kg) and apomorphine (5 mg/kg). Clozapine (2.5 mg/kg) reduced the stereotyped behavior produced by amphetamine (2 mg/kg) but did not exert any action on apomorphine effects. It is suggested that clozapine suppression of the tonic effects originating from the lateral parts of the caudate nucleus is responsible for poor intensity of extrapyramidal disorders seen in clinical application of this agent.

Central dopamine receptors regulate blood eosinophilia in the rat

Dopaminergic agents, dopa and apomorphine, affected biphasically the blood eosinophil count in the rat: low doses of the drug elevated, while high doses lowered it. The response to a high dose of dopa was retained in rats pretreated with an inhibitor of dopamine-beta-hydroxylase, U 10, 157, but prevented by a centrally acting dopa decarboxylase inhibitor, NSD 1015. This indicates that the eosinopenia observed after large doses of dopa is due to the action of dopamine formed from the precursor. As intracerebroventricular injections of Ldopa also produce eosinopenia, the central site of dopamine action is indicated. The eosinopenic response to apomorphine was antagonized by a dopamine receptor blocking agent, haloperidol. This indicates that some central dopamine receptors are involved in the regulation of the eosinophil count in circulating blood. The hypophysis seems to play a crucial role in the phenomenon observed, as no eosinopenia was produced by dopa in hypophysectomized rats.

Synthesis of catecholamines in the eye after local injection of 3H-precursors

The possibility that adrenaline may be synthesized locally in the eye was investigated in the rabbit and vervet monkey. L-tyrosine-3,5-3H, L-tyrosine (side-chain-2,3-3H) or L-3,4-dihydroxyphenylalanine (3H(G)) was injected into the anterior chamber or the vitreous. The animals were killed after 1/2 h up to 7 days in the tyrosine experiments and after 1 up to 24 h in the DOPA experiments. The synthesis of 3H-adrenaline, 3H-noradrenaline and 3H-dopamine was measured with a modified version of a double isotope technique for determination of catecholamines. No 3H-adrenaline was found. An attempt to stimulate the phenylethanolamine-N-methyltransferase activity with a glucocorticoid and to inhibit the metabolism of catecholamines with a monoaminoxidase inhibitor also failed to demonstrate 3H-adrenaline synthesis. 3H-noradrenaline was found in all experiments when 3H-DOPA had been given. The amounts were about 10 times higher after injection into the anterior chamber than after injection into the vitreous. 3H-dopamine was found in all except a few experiments after 3H-DOPA injection. The highest amounts were found after injection into the vitreous. In experiments with 3H-tyrosine we were unable to demonstrate any catecholamine synthesis. This prompts the question of whether tyrosine-hydroxylase may be absent in the eyes of certain animal species.

[Influence of DOPA, dopamine and melatonin on adrenal function in rats]

Experiments were conducted on Wistar rats, 160 to 180 g in weight. Epiphysectomy and pseudoepiphysectomy were carried out 14 days before the main experiment. Adrenal gland function was assessed by the rate of secretion of aldosterone and corticosterone into the adrenal vein and by the content of adrenaline in the adrenal glands. DOPA, dopamine and melatonine were administered into the third cerebral ventricle in a dose of 1 gamma per 100 g of weight, and intravenously in a dose of 100 gamma per 100 g of weight. Intraperitoneally melatonin was injected in a dose of 1 mg/100 g twice a day for 3 days. It was shown that administration of DOPA to males and of dopamine to females into the third ventricle of the brain increased the rate of aldosterone secretion in the intact rats. With different methods of administration melatonine decreased the rate of aldosterone and corticosterone secretion in the intact rats. Intravenous injection of melatonine to epiphysectomized rats stimulated the rate of secretion of the mentioned hormones.