[Myocardiopathy and isolated glucocorticoid deficit with ACTH resistance: a fortuitous association?]. / Myocardiopathie et déficit isolé en glucocorticoïdes par résistance à l'ACTH: une association fortuite?

UNLABELLED: Hereditary syndrome of unresponsiveness to ACTH is a rare autosomal recessive disorder characterized by an isolated glucocorticoid deficiency which is exceptionally associated to regressive cardiomyopathy. CASE REPORT: A male newborn had iterative episodes of hypoglycemia since the first hours of life. Acute bronchiolitis at the age of 14 days was associated with transitory dilated cardiomyopathy. Hypoglycemia was due to glucocorticoid deficiency secondary to ACTH insensitivity. Molecular biology showed a composite heterozygotism for the ACTH receptor gene. CONCLUSION: Any congenital glucocorticoid deficiency should lead to search for cardiomyopathy.

The platelet activating factor receptor antagonist, RP 59227, blocks platelet activating factor receptors mediating liberation of reactive oxygen species in guinea pig macrophages and human polymorphonuclear leukocytes.

In elicited (mineral oil) peritoneal guinea pig macrophages, there was a specific [3H]platelet activating factor (PAF) binding which displayed concentration dependency, saturability, high affinity (Kd = 2.2 +/- 0.2 nM, n = 15), elevated capacity (Bmax = 122,808 +/- 10,234 sites/cell, n = 15) and irreversibility. PAF(C16) and the PAF antagonists RP 59227, Ro 19-3704 and WEB 2086 prevented the binding of [3H]PAF. RP 59227 (Ki = 3.1 +/- 0.3 nM, n = 5) was about 5- and 8-fold more potent than Ro 19-3704 and WEB 2086, respectively. In competition studies, RP 59227 produced dextral and concentration-dependent shifts of the sigmoidal inhibition curve of [3H]PAF binding by PAF(C16). Macrophages exposed to PAF produced chemiluminescence signals, the magnitude of which was concentration related (pD2 = 8.40 +/- 0.03, n = 13) and which were inhibited by the oxygen radical scavengers, superoxide dismutase, catalase, deferoxamine and mannitol. RP 59227 and WEB 2086 antagonized in a noncompetitive manner (pD'2 = 7.72 +/- 0.01 and 8.15 +/- 0.05, respectively) the control PAF concentration-response curve. By contrast, Ro 19-3704 behaved as a competitive antagonist (pA2 = 8.13 +/- 0.11). The apparent noncompetitive effects of RP 59227 were not due to undisplaceable binding to PAF receptors because washing of macrophages exposed to RP 59227 allowed the recovery of PAF luminescence and PAF binding. This procedure was poorly effective to lessen the inhibitory activity of WEB 2086. In human polymorphonuclear leukocytes, the weak potency of PAF was enhanced by 10-fold (pD2 = 7.61 +/- 0.06, n = 6) when polymorphonuclear leukocytes were primed for 10 min with fMLP (5 nM).(ABSTRACT TRUNCATED AT 250 WORDS)

Functional validation of platelet-activating factor receptor sites characterized biochemically by a specific and reproducible [3H]platelet-activating factor binding in human platelets.

In human platelet membranes, [3H]platelet-activating factor(PAF)-C18 binding sites exhibited high affinity (Kd 0.074 +/- 0.005 nM, n = 28 healthy volunteers), saturability, elevated stereoselectivity, marked pharmacological specificity and small intersubject variability. The maximal binding capacity was 215 +/- 12 fmol/mg protein. Saturation of [3H]PAF binding was obtained with 0.3 nM ligand, and its isotherm was compatible with a single class of binding sites. The stereoselectivity for [3H]PAF was clearly indicated by the low displacing potency of enantio-PAF-C16 (the synthetic enantiomer of PAF) that was 5000-fold less potent than PAF. Specific [3H]PAF binding attained 65% with 0.1 nM ligand and was displaced fully not only by cold PAF but also by RP 59227 (Ki = 6.2 +/- 1.3 nM, n = 7), a novel, potent and specific PAF receptor antagonist in a pure enantiomeric form and several other antagonists such as CV-6209, WEB 2086, L-652,731 and BN 52021. Various classical pharmacological agents did not interfere with the [3H]PAF binding. In intact platelets, [3H]PAF binding shared the same properties as those just described for membrane preparations. A functional role for these binding sites was suggested by the high correlation (r = 0.94, P less than .001) between the Ki values for several known PAF antagonists determined in [3H]PAF binding and the IC50 values obtained against PAF-induced aggregation in whole platelets. Thus, the present [3H]PAF binding in human platelet membranes may be a useful pharmacological tool to study possible changes in [3H]PAF binding parameters induced by pathological states for which PAF may be directly or indirectly responsible.

High affinity specific binding sites for tritiated platelet-activating factor in canine platelet membranes: counterparts of platelet-activating factor receptors mediating platelet aggregation.

In canine platelet membranes, tritiated platelet activating factor (PAF) labels in a saturable and reversible manner a single population (nH = 0.97) of binding sites. The affinity of this binding was high (Kd = 0.23 +/- 0.02 nM, n = 4, and 0.21 +/- 0.05, n = 8, determined by kinetics or saturation experiments, respectively), and the density of binding sites (Bmax) was 911 +/- 31 fmol/mg of protein (n = 8). [3H]PAF binding was entirely reversed by unlabeled PAF (10 microM). [3H]PAF exhibited stereoselective discrimination inasmuch as it was poorly displaced by enantio-PAF, the PAF enantiomer that does not occur naturally. Furthermore, the displacing potency of the (+)-enantiomer of the PAF antagonist 52770 RP against [3H]PAF was 45 times higher than that of the (-)-enantiomer. [3H]PAF binding displayed a remarkable specificity in that it was not affected by a variety of classical pharmacological agents. However, this binding was displaced by several PAF receptor antagonists such as 59227 RP, CV-6209, Ro 19-3704, 52770 RP, brotizolam, WEB 2086, SRI 63-441, L-652,731, alprazolam, triazolam, and BN 52021. The Ki of the 16 studied antagonists ranged from 7.9 nM (59227 RP, most potent) to 16.8 microM (BN 52021, least potent). The possible biological significance of our binding procedure was assessed by correlating the potencies of 16 PAF antagonists as [3H]PAF displacers in dog platelet membranes and as inhibitors of PAF-induced platelet aggregation in washed canine platelets. This analysis revealed the existence of a highly significant correlation (r = 0.82, p less than 0.001) between biochemical and functional tests. However, two compounds (Ro 19-3704 and BN 52021) were found to be located outside the confidence limits when the probability level of belonging to the regression line was set at 0.01. In conclusion, this study provides evidence that [3H]PAF binding in canine platelet membranes exhibits the required properties for a valid binding procedure. Furthermore, the labeled sites are likely to be the counterparts of platelet receptors that, when activated by PAF, induce aggregation.

Effect of chronic treatment with selective monoamine oxidase inhibitors and specific 5-hydroxytryptamine uptake inhibitors on [3H]paroxetine binding to cerebral cortical membranes of the rat.

[3H]Paroxetine is a highly selective ligand for the 5-hydroxytryptamine transporter complex and the specific binding of this ligand to membrane fractions from cerebral cortex or hippocampus was studied in rats treated with specific inhibitors of the uptake of 5-hydroxytryptamine and monoamine oxidase inhibitors. The Kd and Bmax of the binding of [3H]paroxetine to cerebral cortical membranes of the rat was unaffected, compared to sham controls, by either acute or chronic administration with citalopram or chlorimipramine. Also, chronic treatment with chlorimipramine did not alter the parameters of the binding of [3H]paroxetine to hippocampal membranes from the rat compared to sham controls. Furthermore, chronic and acute treatments with clorgyline or deprenyl did not produce any significant changes in the Kd and Bmax of the binding of [3H]paroxetine to cerebral cortical membranes in the rat. These findings on the binding of [3H]paroxetine are discussed in light of previous equivocal results on the plasticity of neuronal binding sites for [3H]imipramine after various pharmacological treatments.

Characterization of [3H]paroxetine binding to rat cortical membranes.

Paroxetine is a selective and potent inhibitor of 5-hydroxytryptamine uptake into serotonergic neurons. The specific binding of [3H]paroxetine to rat cortical membranes at 22 degrees C was examined in this study. Our results indicate the presence of a single saturable high affinity binding component for [3H]paroxetine. Scatchard analysis revealed a Kd of 0.15 +/- 0.01 nM, and a Bmax of 549 +/- 36 fmol/mg protein. The kinetically derived dissociation constant was 0.034 +/- 0.008 nM. [3H]Paroxetine binding was inhibited selectively by 5-HT uptake blockers, and a good correlation was demonstrated between the potency of various drugs to inhibit [3H]paroxetine binding and [3H]5-hydroxytryptamine uptake. Also, lesions performed with the neurotoxin, 5,7-dihydroxytryptamine resulted in a 94% decrease in endogenous 5-hydroxytryptamine levels and concomitantly, a 90% reduction in [3H]paroxetine binding when compared to sham controls. These results indicate that the binding site labelled by [3H]paroxetine is associated with the neuronal 5-hydroxytryptamine transporter complex.