Biomedical subjects

F Amenta

Publications and source records attributed to F Amenta.

At least 55 records · Page 3Linked to original sources

PubMed1999

Dopamine D2-like receptors on human peripheral blood lymphocytes: a radioligand binding assay and immunocytochemical study.

1. Peripheral blood lymphocytes express dopamine D1-like and D2-like receptors which were investigated using radioligand binding assay and molecular biology techniques. Analysis of dopamine D2-like receptors expressed by human peripheral blood lymphocytes with radioligand binding assay may offer a rapid technique for assessing receptor changes in disorders characterized by involvement of the dopaminergic system. However, the suitability of radioligand binding assay techniques to measure dopamine D2-like receptors is questioned. 2. In view of the discrepancy between data of dopamine D2-like receptor determination with molecular biology and radioligand binding assay techniques, we have assayed dopamine D2-like receptors expressed by human peripheral blood lymphocytes using as radioligands the dopamine receptor agonist 7-[3H]-hydroxy-N,N-di-n-propyl-2-aminotetraline ([3H]-7-OH-DPAT) and two antagonists ([3H]-spiperone and [3H]-nemonapride). 3. Analysis of saturation curves revealed a concentration-dependent binding of all compounds to human peripheral blood lymphocytes. Dissociation constant (Kd) values averaged between 0.15 and 0.40 nM for different radioligands. The maximum density of binding sites (Bmax) was low, ranging from 4.15 +/- 0.05 fmol/10(6) cells with [3H]-spiperone and 8.66 +/- 0.04 fmol/10(6) cells with [3H]-7-OH-DPAT. 4. Displacement curves of [3H]-7-OH-DPAT, [3H]-spiperone and [3H]-nemonapride binding to human peripheral blood lymphocytes revealed, using radioligand concentrations giving the highest specific:non-specific binding ratio, a pharmacological profile consistent with the labelling of dopamine D2-like receptors. The use of higher radioligand concentrations resulted in a poorly displaceable and characterizable binding. 5. Detection of dopamine D2, D3 and D4 receptor immunoreactivity in cytospin centrifuged peripheral blood lymphocytes revealed dopamine D3 and D4 but not D2 receptor immunostaining. 6. The above findings indicate in agreement with molecular biology studies, that dopamine D2-like receptors expressed by human peripheral blood lymphocytes belong to the D3 and D4 receptor subtypes. These receptors are detectable using either dopamine D2-like receptor agonists and antagonists as radioligands if controlled experimental conditions are followed. The standardisation of immunocytochemical techniques for detecting human peripheral blood lymphocyte dopamine receptors may contribute to clarify their role in lymphocyte function or as a peripheral marker of the status of the dopaminergic system.

Benzamides↗

PubMed1999

alpha1-adrenergic receptor subtypes in human peripheral blood lymphocytes.

We investigated the expression of alpha1-adrenergic receptor subtypes in intact human peripheral blood lymphocytes using reverse transcription-polymerase chain reaction (RT-PCR) and radioligand binding assay techniques combined with antibodies against the three subtypes of alpha1-adrenergic receptors (alpha1A, alpha1B, and alpha1D). RT-PCR amplified in peripheral blood lymphocytes a 348-bp alpha1A-adrenergic receptor fragment, a 689-bp alpha1B-adrenergic receptor fragment, and a 540-bp alpha1D-adrenergic receptor fragment. Radioligand binding assay with [3H]prazosin as radioligand revealed a high-affinity binding with a dissociation constant value of 0. 65+/-0.05 nmol/L and a maximum density of binding sites of 175. 3+/-20.5 fmol/10(6) cells. The pharmacological profile of [3H]prazosin binding to human peripheral blood lymphocytes was consistent with the labeling of alpha1-adrenergic receptors. Antibodies against alpha1A-, alpha1B-, and alpha1D-receptor subtypes decreased [3H]prazosin binding to a different extent. This indicates that human peripheral blood lymphocytes express the three alpha1-adrenergic receptor subtypes. Of the three different alpha1-adrenergic receptor subtypes, the alpha1B is the most represented and the alpha1D, the least. Future studies should clarify the functional relevance of alpha1-adrenergic receptors expressed by peripheral blood lymphocytes. The identification of these sites may represent a step for evaluating whether they represent a marker of alpha1-adrenergic receptors in cardiovascular disorders or for assessing responses to drug treatment on these receptors.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1999

Sulphatides in the brain of spontaneously hypertensive rats.

Sulphatides were assayed in preparations of frontal cortex, neostriatum and hippocampus of 6-month-old male spontaneously hypertensive rats (SHR, systolic pressure 215 +/- 6 mmHg) and age-matched normotensive Wistar-Kyoto (WKY) rats (systolic pressure 143 +/- 6 mmHg) by thin layer chromatography associated with spectrophotometry and histochemistry. The volume of gray and white matter of the above areas was also measured by microanatomical techniques associated with image analysis. Sulphatide levels were unchanged in the frontal cortex and neostriatum and decreased in the hippocampus of SHR in comparison with WKY rats. No changes of metachromatic sulphatide staining were found in the different brain areas investigated of SHR, whereas a decrease of positive metachromatic areas was noticeable in the frontal cortex and neostriatum, but not in the hippocampus of SHR. A reduction of volume of frontal cortex gray and white matter as well as of striosomes and of gray matter of hippocampus was found in SHR. No changes in the total volume of neostriatum and in the volume of white matter of hippocampus were observed between SHR and normotensive WKY rats. These findings, which are consistent with recent evidence of the occurrence of atrophic changes in the brain of SHR, showed that sulphatide levels were decreased in the hippocampus of SHR. In this area no reduction of white matter was observed. Sulphatide concentrations are thought to reflect the status of brain myelinated fibers. The not parallel decrease of sulphatide levels and white matter volume in the majority of brain areas investigated suggests the occurrence in SHR of sulphatide changes not corresponding simply to a reduction of myelinated pathways.

Animals↗

PubMed1998

Sensitivity to ageing of the limbic dopaminergic system: a review.

The limbic system includes the complex of brain centres, nuclei and connections that provide the anatomical substrate for emotions. Although the presence of small amounts of dopamine (DA) in several limbic structures has been recognized for a long time, for many years it was thought that limbic DA represented a precursor of noradrenaline in the biosynthetic pathway of catecholamines. More recent evidence has shown that limbic centres and nuclei are supplied with a dopaminergic innervation arising from the ventral tegmental area (field A10) and in smaller amounts from the mesencephalic A9 field. The dopaminergic limbic system is sensitive to ageing. Parameters of dopaminergic neurotransmission (DA levels, biosynthetic and catabolic markers and DA receptors) undergo age-related changes which depend on the structure and species investigated and are characterized mainly by a decline of different parameters examined. In this paper, the influence of ageing on DA biosynthesis, levels, metabolism and receptors are reviewed in laboratory rodents, monkeys and humans as well as in cases of Alzheimer's disease and Parkinson's disease. The possibility that changes of dopaminergic neurotransmission markers in the limbic system are associated with cognitive impairment and psychotic symptoms affecting the elderly is discussed. Better knowledge of dopaminergic neurotransmission mechanisms in the so-called physiological ageing and in senile dementia may provide new insights in the treatment of behavioural alterations frequently occurring in old age.

Aging↗

PubMed1998

Labeling of dopamine D3 and D4 receptor subtypes in human peripheral blood lymphocytes with [3H]7-OH-DPAT: a combined radioligand binding assay and immunochemical study.

Molecular biology studies have demonstrated that human peripheral blood lymphocytes express dopamine D2-like receptors belonging to the D3 and D4 receptor subtypes, whereas the characterization of these receptors using radioligand binding assay techniques provided conflicting results. The preferential dopamine D3 receptor agonist [3H]7-hydroxy-N, N-di-n-propyl-2-aminotetralin ([3H]7-OH-DPAT) was used recently for labeling lymphocyte dopamine D3 receptor. However, the selectivity of this compound for the D3 receptor was questioned. In this study we have investigated human peripheral blood lymphocyte dopamine receptor subtypes labeled by [3H]7-OH-DPAT using a conventional radioligand binding assay technique and antibodies against dopamine D2-like receptor subtypes. [3H]7-OH-DPAT was specifically bound to intact human peripheral blood lymphocytes with a dissociation constant (Kd) value of 0.32 + 0.03 nM and a maximum density of binding sites (Bmax) of 18.2 + 0.8 fmol/2 x 10(6) cells. [3H]7-OH-DPAT binding was unaffected by antibodies against dopamine D2 and D2S receptors. Anti-dopamine D3 and D4 receptor antibodies reduced [3H]7-OH-DPAT binding by about 53% and 32% respectively. Combination of anti D3 and D4 receptor antibodies reduced remarkably [3H]7-OH-DPAT binding. The above results suggest that the dopamine receptor agonist [3H]7-OH-DPAT labels dopamine D3 and D4 receptor subtypes in human peripheral blood lymphocytes. The use of antibodies raised against dopamine receptor subtypes in combination with radioligand binding assay may contribute to define receptor subtypes expressed by human peripheral blood lymphocytes in health and disease.

Adult↗

PubMed1998

Astrocyte changes in aging cerebral cortex and hippocampus: a quantitative immunohistochemical study.

Glial cells are sensitive to aging, but the real extent of age-related quantitative and qualitative changes of these brain cellular elements has not yet been clarified. Brain volume undergoes age-related changes, but several studies on the number of glial cells have not taken this important variable into account. In this study we quantitatively evaluated the number and morphology of glial fibrillary acidic protein (GFAP)-immunoreactive astroglia in the frontal cortex and in the CA1 subfield of the hippocampus of male Sprague-Dawley rats of aged 12 and 24 months, considered adult and aged, respectively. The volume of frontal cortex was unchanged in the two age groups investigated, whereas the volume of hippocampus was higher in aged rats. An increase in the number and size of GFAP-immunoreactive astrocytes was observed in the frontal cortex and in the CA1 subfield of the hippocampus of aged rats. The numeric increase in astrocytes was more pronounced in the hippocampus than in the frontal cortex, whereas age-related hypertrophy of astroglia was more accentuated in the frontal cortex. The possible significance of hyperplasia and hypertrophy of GFAP-immunoreactive astrocytes in the frontal cortex and in the CA1 subfield of the hippocampus of aged rats is discussed.

Age Factors↗

PubMed1998

Effect of lesions of the nucleus basalis magnocellularis and of treatment with posatirelin on cholinergic neurotransmission enzymes in the rat cerebral cortex.

The effect of 4 and 8 weeks of treatment with the thyrotropin releasing hormone (TRH), analogue posatirelin (L-6-ketopiperidine-2-carbonyl-L-leucyl-proline amide), on the changes of cholinergic neurotransmission enzymes, choline acetyltransferase (ChAT) and acetylcholinesterase (AChE), caused by lesions of the nucleus basalis magnocellularis (NBM), was investigated in the rat frontal cortex. ChAT and AChE were demonstrated with immunohistochemical and histochemical techniques, respectively associated with image analysis and microdensitometry. Monolateral and bilateral lesions of NBM area caused a significant loss of ChAT-immunoreactive nerve cell bodies in the NBM, as well as a remarkable decrease of ChAT-immunoreactive fibres and of AChE reactivity in the frontal cortex ipsilateral to the lesion or of both sides, respectively. The number of ChAT-immunoreactive nerve cell bodies in the lesioned NBM was higher in posatirelin-treated rats for 8 weeks in comparison with control NBM-lesioned rats. Moreover, the compound increased the number of ChAT-immunoreactive fibres in the frontal cortex of monolaterally and bilaterally NBM-lesioned rats at 8 weeks after lesion, but was without effect on these fibres in sham-operated rats. The same is true for AChE reactivity, developed in the neuropil of the frontal cortex, which was restored in part by an 8-week treatment with posatirelin in NBM-lesioned rats. These findings suggest that treatment with posatirelin rescues cholinergic neurons of the NBM and cholinergic projections to the cerebral cortex affected by lesioning of the NBM. The functional relevance of these observations and their possible applications should be evaluated in future studies.

Acetylcholinesterase↗

PubMed1998

Influence of neonatal treatment with the pyrethroid insecticide cypermethrin on the development of dopamine receptors in the rat kidney.

The influence of neonatal treatment with the pyrethroid insecticide cypermethrin ((R,S)alpha-cyano-3-phenoxybenzyl (1R,S)-cis-trans-3-(2,2-dichloro-vinyl)-2,2-dimethylcyclopropane carboxylate) on postnatal development of renal dopamine receptors was investigated by radioligand binding assay techniques. Treatment with cypermethrin was made on rats from the 10th to the 16th day after birth. Dopamine D1- and D2-like receptors were assayed in frozen sections of kidney of 21-, 30-, 60- and 90-day-old rats using as ligands of dopamine D1- and D2-like receptors [3H]([R](+)-(chloro-2,3,4,5,-tetrahydro-5-phenyl-1,4,-benzazepinal hemimaleate) (SCH 23390) and [3H]spiperone, respectively. Treatment with cypermethrin was without effect on the affinity (Kd value) or the density (Bmax value) of dopamine D1- and D2-like receptors of rats of 21 days of age. In older groups, treatment with the compound reduced the affinity and increased the density of dopamine D1-like receptors, whereas it was without effect on the affinity of dopamine D2-like receptors and decreased their density. These findings indicate that neonatal treatment with the pyrethroid insecticide cypermethrin induces long-lasting impairment of renal dopamine D1- and D2-like receptors and that kidney is a target of the toxic action of the compound. Renal dopamine receptor changes caused by cypermethrin are consistent with possible alterations of renal tubular function and of sympathetic neuroeffector modulation. The above data suggest also that, different from the adult, neonatal exposure to pyrethroid insecticides may induce toxic effects.

Animals↗

PubMed1998

Autoradiographic localisation of muscarinic cholinergic receptor subtypes in human placenta.

The localisation of M1-M4 muscarinic cholinergic receptor subtypes was investigated in sections of normal human term placenta by light microscope autoradiography. Muscarinic cholinergic receptor subtypes were found almost exclusively in syncytiotrophoblast. Neither other cellular components of placenta, nor blood vessels were labelled. Quantitative analysis of the density of silver grains developed in sections incubated with the different protocols for labelling M1-M4 receptor subtypes, revealed that syncytiotrophoblast expresses all subtypes of muscarinic cholinergic receptor investigated. A higher density of binding sites was found in the apical than in the basal portion of syncytiotrophoblast. The demonstration of muscarinic cholinergic receptors in syncytiotrophoblast suggests that a cholinergic system may have a role in regulating transport of compounds from maternal to foetal interface.

Adult↗

PubMed1998

Dopamine D2-like receptors in the kidney of spontaneously hypertensive rats: a radioligand binding assay and light microscope autoradiography study.

1. Dopamine D2-like receptors were investigated in sections of kidney from male spontaneously hypertensive rats (SHRs) at 6 and 14 weeks of age using radioligand binding assay and autoradiographic techniques with [3H]-spiperone as a ligand. 2. Systolic blood pressure values were slightly higher in 6-week-old SHRs in comparison with age-matched normotensive Wistar-Kyoto (WKY) rats and considerably higher in 14-week-old SHRs in comparison with the other groups investigated. Renal dopamine levels were higher in SHRs aged 6 and 14 weeks in comparison with age-matched WKY rats. Noradrenaline concentrations were similar in 6-week-old SHRs and normotensive WKY rats, and increased slightly in SHRs aged 14 weeks. 3. The density of [3H]-spiperone binding sites was similar in SHRs and WKY rats at 6 weeks of age, and decreased in SHRs at 14 weeks in comparison with age-matched normotensive animals. Light microscope autoradiography revealed the accumulation of silver grains in the tunica adventitia, in the adventitia-media border of intrarenal arteries and within cortical tubules. A few specific silver grains were also developed in the glomerular tuft. No changes in the density and pattern of silver grains were noticeable between SHRs and WKY rats at 6 weeks of age, whereas a reduction in silver grains largely affecting vascular binding sites was observed at 14 weeks of age. 4. Renal denervation considerably decreased the density of [3H]-spiperone binding sites in sections of rat kidney, with an almost complete loss of vascular binding sites. 5. The above findings indicate the occurrence of a decrease of dopamine D2-like receptors in the kidney of SHRs with the progress of hypertension. Dopamine D2-like receptors which are mainly prejunctional are involved in the modulation of sympathetic neurotransmission in the kidney. The loss of these receptors in SHRs may contribute to the pathophysiology of hypertension.

Adrenergic alpha-Agonists↗

PubMed1998

Pharmacological characterization and autoradiographic localization of a putative dopamine D4 receptor in the heart.

1. The pharmacological profile and the anatomical localization of a putative dopamine D4 receptor were assessed in sections of rat and human atria and ventricles using combined radioligand binding and autoradiographic techniques with [3H]-spiperone as a ligand. 2. [3H]-Spiperone was bound specifically to sections of human and rat atria and ventricles. The binding was time-, temperature- and concentration-dependent, belonging to a single class of high-affinity sites. In atria, the dissociation constant value (Kd) was 0.45 nM in rats and 0.32 nM in humans, and the maximum density of binding sites (Bmax) was 31.6+/-2.9 fmol mg(-1) tissue in rats and 18.8+/-0.7 fmol mg(-1) tissue in humans. In ventricles, Kd was 0.38 nM in rats and 0.39 nM in humans, and the Bmax was 43.5+/-3.0 fmol mg(-1) tissue in rats and 56.4+/-3.2 fmol mg(-1) tissue in humans. 3. The pharmacological profile of [3H]-spiperone binding to sections of both rat and human atria and ventricles was consistent with the labelling of dopamine D2-like receptors. [3H]-Spiperone binding was more sensitive to displacement by the neuroleptic clozapine in sections of atria than of ventricles, suggesting the expression of a dopamine D4 receptor in atrial tissue. Moreover, preincubation of some sections with a dopamine D4 receptor antibody and subsequent exposure to [3H]-spiperone caused a remarkable decrease of radioligand binding to sections of atria, but only a slight reduction of binding to sections of ventricles. 4. Light microscope autoradiography revealed the accumulation of silver grains over atrial tissue within atrial myocardiocytes. A higher density of silver grains was developed in rat than in human atria. In ventricles, silver grains were accumulated primarily in cluster areas both in rats and in humans. 5. The above findings suggest the expression of a dopamine D4 receptor in rat atria, but not in ventricles. A similar site was identified in human atria. The possible relevance of a dopamine D4 receptor in the heart is discussed.

Adolescent↗

PubMed1998

Peripheral blood lymphocyte muscarinic cholinergic receptors in airway hyperresponsiveness: a marker of cholinergic dysfunction?

1. Muscarinic cholinergic receptors were assayed in human peripheral blood lymphocytes of healthy control and airway hyperresponsive subjects using a radioligand binding assay technique and the muscarinic cholinergic receptor antagonist [3H]-quinuclidinyl benzilate (QNB) as a radioligand. Subjects investigated were divided in four different groups based on threshold responses to methacholine inhaled as challenge test. 2. [3H]-QNB was bound to human peripheral blood lymphocytes in a manner consistent with the labelling of muscarinic cholinergic receptors. Dissociation constant (Kd) values of [3H]-QNB binding were similar in the different groups examined, whereas maximum density of binding sites (Bmax) was increased in airway hyperresponsive subjects in comparison with healthy controls. 3. The above findings indicate that the density of muscarinic cholinergic receptors is increased in peripheral blood lymphocytes of airway hyperresponsive subjects. 4. This suggests that airway hyperresponsiveness is associated with cholinergic hyperreactivity and is probably a systemic cholinergic dysfunction since it is accompanied by changes in the density of muscarinic cholinergic receptors expressed by peripheral blood lymphocytes.

Adult↗

PubMed1998

Association of circulating endothelium and noradrenaline with increased calcium-channel binding sites in the placental bed in pre-eclampsia.

OBJECTIVE: To evaluate factors contributing to both placental hypoperfusion and maternal vasoconstriction in pre-eclampsia. DESIGN: Single centre, comparative study of calcium-channel density and affinity in the placental bed of pregnant women with normotension and pre-eclampsia. SETTING: Teaching hospital. PARTICIPANTS: Twenty-two primigravidae in the third trimester of pregnancy: 10 with pre-eclampsia and 12 normotensive. METHODS: Plasma levels of endothelin-1 (by RIA) and noradrenaline (by HPLC-ED) were measured. Both pharmacological characterisation and anatomical localisation of dihydropyridine-sensitive binding sites (using radioligand-binding studies and autorradiographic techniques) were determined with 3H-isradipine in placental bed tissues to determine both the density (Bmax) and the affinity (Kd) of receptor sites. RESULTS: Higher plasma levels of endothelin-1 and noradrenalin were found in women with pre-eclampsia compared with normotensive women. Placental bed tissues bound 3H-isradipine in a saturable, reversible time and temperature-dependent manner with very low Kd values. Study of the 3H-isradipine specificity binding included the use of several dihydropyridine displacers. In the group with pre-eclampsia the Scatchard analysis of the results showed a significant increase (P < 0.001) both in the affinity [Kd = 0.23 nmol (0.04) vs 0.45 nmol (0.03), pre-eclampsia vs normotensive] and in the density of calcium-channel binding sites [Bmax = 77.70 fmol/mg (1.30) vs 64.30 fmol/mg (1 80) tissue, pre-eclampsia vs normotensive]. Autoradiography confirmed that in the placental bed tissue of those with pre-eclampsia there was a much higher silver grain density in the arteries walls, compared with normotensive women. CONCLUSIONS: In pre-eclampsia there is an increase in the maternal circulation of two strong vasoconstrictor factors (endothelin-1 and noradrenalin) and a sharp increase both in the density and the affinity of calcium-channel binding sites in placental bed central area. The latter may strongly contribute to the perpetuation of the uteroplacental hypoperfusion either by itself or by amplifying the local actions of circulating factors, such as endothelin-1 and noradrenalin.

Adult↗

PubMed1998

Telemedicine and medical care to ships without a doctor on board.

Providing medical assistance to ships at sea was probably one of the first practical applications of telemedicine. At present, about 200 different organizations worldwide give medical assistance to ships without a doctor on board. The activity of the Foundation Centro Internazionale Radio Medico (CIRM), which probably has the largest experience in the world of telemedicine applied to seafarers, is reviewed. Medical assistance to seafarers has not improved in parallel with advances in medicine and telecommunications. Possible initiatives for improving teledelivery of medical assistance to seafarers are discussed.

Humans↗

PubMed1998

Density and localization of calcium channels of the L-type in human pulmonary artery.

The pharmacological profile and the anatomical localization of Ca2+ channels of the L-type were investigated in the human pulmonary artery to identify possible mechanisms involved in the regulation of the pulmonary vascular tone. Analysis was performed on slide-mounted frozen sections of human pulmonary artery using radioligand binding assay techniques associated with light microscope autoradiography. [3H]-Nicardipine was used as ligand. Human renal and right coronary arteries also were used as systemic reference arteries. Binding of [3H]-nicardipine to sections of human pulmonary artery was time-, temperature- and concentration-dependent, saturable and reversible. In the human pulmonary artery, the apparent equilibrium dissociation constant (Kd) was 0.12+/-0.02 nM and the maximum density of binding sites (Bmax) was 38.15+/-2.25 fmol/mg tissue. Kd values were 0.3+/-0.01 nM and 0.5+/-0.02 in the human renal artery and right coronary artery respectively. Bmax values were 248+/-16 fmol/mg tissue and 173+/-9.5 fmol/mg tissue in the human renal artery and right coronary artery respectively. The pharmacological profile of [3H]-nicardipine binding to sections of human pulmonary artery was consistent with the labeling of Ca2+ channels of the L-type. It was similar in the pulmonary artery and in the human renal and right coronary arteries. Light microscope autoradiography revealed a high density of [3H]-nicardipine binding sites within smooth muscle of the tunica media of human pulmonary artery as well as of human renal and right coronary arteries. A lower accumulation of the radioligand occurred in the tunica adventitia. No specific binding was noticeable in the tunica intima. Our data suggest that human pulmonary artery expresses Ca2+ channels of the L-type sensitive to dihydropyridines. These sites have similar affinity and lower density than those expressed by systemic arteries. The presence of Ca2+ channels of the L-type in human pulmonary artery suggests that their pharmacological manipulation may be considered in the treatment of pulmonary hypertension.

Aged↗

PubMed1997

Pharmacological characterisation and autoradiographic localisation of a putative dopamine D3 receptor in the rat kidney.

The pharmacological profile and the microanatomical localisation of a putative dopamine D3 receptor in the rat renal cortex were investigated using radioligand binding assay and light microscope autoradiography techniques. [3H]7-hydroxy-N,N-di-n-propyl-2-aminotetraline ([3H]7-OH-DPAT) was used as a ligand. [3H]7-OH-DPAT was bound specifically to sections of renal cortex. The binding was time-, temperature- and concentration-dependent, of high affinity and guanine nucleotide-insensitive. The dissociation constant (Kd) value was 0.57 +/- 0.02 nM and the maximum density of binding sites (Bmax) was 62.4 +/- 3.5 fmol/mg tissue. The pharmacological profile of [3H]7-OH-DPAT binding to sections of rat renal cortex suggests the labelling of a dopamine D3 receptor. Light microscope autoradiography revealed the accumulation of the radioligand primarily within cortical tubules and to a lesser extent in the glomerular tuft. In glomeruli, binding sites were found mainly in mesangium and mesangial cells. The demonstration of a putative dopamine D3 receptor in slide-mounted sections of rat renal cortex suggests that appropriate radioligand binding assay techniques combined with autoradiography, may contribute to characterise peripheral dopamine receptor subtypes.

Animals↗

PubMed1997

Dopamine D2-like receptors in the rat kidney: effect of denervation.

The effects of monolateral denervation induced by renal artery occlusion on dopamine D2-like receptors were assessed in rat kidney using radioligand binding assay and autoradiographic techniques. [3H]spiperone was used as a ligand. [3H]spiperone was bound specifically to sections of control innervated kidneys with a dissociation constant (Kd) value of 0.07 +/- 0.003 nM and a maximum density of binding sites (Bmax) value of 35.4 +/- 0.16 fmol/mg tissue. Light microscope autoradiography showed the accumulation of silver grains both in the arterial tree and in cortical tubules. At the vascular level, [3H]spiperone binding sites were accumulated primarily in the adventitia and in adventitia-media transitional zone. In cortical tubules, the higher density of [3H]spiperone binding sites was noticeable in proximal convoluted tubules. A few binding sites were also found in the glomerular tuft. In denervated kidneys, noradrenaline and dopamine levels were reduced by about 90% and 60% respectively in comparison with control innervated kidneys. Denervation reduced the density of [3H]spiperone binding sites by more than 85%. In denervated kidneys, light microscope autoradiography showed the disappearance of specific vascular binding sites and a remarkable reduction of tubular [3H]spiperone binding sites. The above results indicate that the largest majority of renal dopamine D2-like receptors labelled by [3H]spiperone is prejunctional in location.

Animals↗

PubMed1997

Dopamine D4 receptor in human peripheral blood lymphocytes: a radioligand binding assay study.

The expression of dopamine D4 receptor was investigated in human peripheral blood lymphocytes with a radioligand binding assay technique, using [3H]clozapine as radioligand. [3H]Clozapine was specifically bound to human peripheral blood lymphocytes. The binding was time-, temperature-, and concentration-dependent and of high affinity, with a dissociation constant (K(d)) value of 0.34 +/- 0.02 nM and a maximum density of binding sites (B(max)) value of 27 +/- 1.4 fmol/10(6) cells. The pharmacological profile of [3H]clozapine binding to human peripheral blood lymphocytes was similar to that found in Chinese hamster ovary (CHO) cells transfected with the D4 clone (D4.2 variant). The above results are consistent with molecular biology studies demonstrating the expression of a dopamine D4 receptor in immune cells and in human peripheral blood lymphocytes. The availability of a rapid and sensitive radioligand binding assay technique for the dopamine D4 receptor in human peripheral blood lymphocytes may contribute to better define the role of this dopamine receptor subtype in neurological and psychiatric disorders.

Adult↗