Search

The cytochemical demonstration of nonspecific alpha-naphthyl acetate esterase (ANAE) actively in human peripheral blood mononuclear cells was studied. Different staining patterns were found, allowing differentiation of mononuclear cells into macrophages (strong granular cytoplasmic activity). B lymphocytes (negative reaction). Tγ lymphocytes, i.e. bearing IgG Fc receptors (granular scattered reaction), and T non-γ lymphocytes, i.e. devoid of IgG Fc receptors (single cytoplasmic ANAE spot). During the early phases of phytohaemagglutinin (PHA)- and contanavalin A (Con A)-induct:d activation, the reactivity of most lymphocytes became granular and scattered similar to that found in Tγ cells. Blast cells generating in successive phases appeared devoid of delectable enzymatic activity. The hypothesis is put forth that T cells showing granular, scattered reactivity represent a population ot" activated cells and that the redistribution of enzymatic activity could represent a preliminary step leading to secretion (lymphokine-like?) of enzyme from cytoplasm in the course of cell activation. [ABSTRACT FROM AUTHOR]

Summary 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 [3 H]-spiperone as a ligand. [3 H]-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. The pharmacological profile of [3 H]-spiperone binding to sections of both rat and human atria and ventricles was consistent with the labelling of dopamine D2 -like receptors. [3 H]-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 section with a dopamine D4 receptor antibody and subsequent exposure to [3 H]-spiperone caused a remarkable decrease of radioligand binding to sections of atria, but only a slight reduction of binding to section of ventricles. 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... [ABSTRACT FROM AUTHOR]

Summary 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 [3 H]-spiperone as a ligand. Systolic blood pressure values were slightly higher in 6-week-old SHRs in comparison with agematched 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. The density of [3 H]-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. Renal denervation considerably decreased the density of [3 H]-spiperone binding sites in sections of rat kidney, with an almost complete loss of vascular binding sites. 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. [ABSTRACT FROM AUTHOR]