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Biomedical subjects

Y C Clement-Cormier

Publications and source records attributed to Y C Clement-Cormier.

At least 19 recordsLinked to original sources
PubMed1982

Selective effects of an essential sulfhydryl group on the activation of dopamine- and guanine nucleotide-sensitive adenylate cyclase.

Treatment of membranes from the dog caudate nucleus with sulfhydryl alkylating agents, N-ethylmaleimide and p-chloromercuribenzoate, results in selective inhibition of dopamine-sensitive adenylate cyclase activity that can be distinguished from effects on basal enzyme activity. Fifty per cent inhibition of dopamine-sensitive adenylate cyclase activity was observed in the presence of 10(-5) M N-ethylmaleimide and 3 X 10(-6) M p-chloromercuribenzoate. N-Ethylmaleimide (10(-5) M or less) also inhibited GTP- and NaF-stimulated adenylate cyclase activity, but had no effect on basal adenylate cyclase activity (assayed in the presence of magnesium) and on enzyme activity assayed in the presence of manganese. The reducing agents dithiothreitol, 2-mercaptoethanol, glutathione, and cysteine had no inhibitory effect on dopamine-sensitive adenylate cyclase activity. Pretreatment of membranes with guanyl-5'-yl imidodiphosphate or guanosine 5'-O-(3-thio)triphosphate prior to incubation with N-ethylmaleimide prevented the inhibitory effect of N-ethylmaleimide on adenylate cyclase activity. The results suggest that a reactive sulfhydryl group in the domain of the GTP-binding protein is important for the coupling of the components of the dopamine-sensitive adenylate cyclase complex in brain.

Adenylyl Cyclase Inhibitors↗
PubMed1981

Regulation of adenylate cyclase activity in GH1 cells by chlorpromazine and a heat-stable factor.

An adenylate cyclase present in a PRL-producing tumor cell line, GH1, which is selectively stimulated by chlorpromazine, has been characterized with respect to several biochemical properties. The parameters studied include divalent metal ion specificity, guanyl nucleotide interaction, and sensitivity to sodium fluoride. The effects of calcium and the calcium chelator, EGTA, were also tested on the chlorpromazine response. The data reported herein establish the optimal conditions for the activation of adenylate cyclase by chlorpromazine in homogenates of GH1 cells. In addition, the results from this study identify a heat-stable protein in these cells which regulates cyclase activity. This protein, which can be released into the supernatant by the pretreatment of GH1 cells with EGTA, is an absolute requirement for chlorpromazine stimulation of adenylate cyclase activity in these cells. The activation of adenylate cyclase by chlorpromazine in homogenates of normal rat pituitaries was demonstrated as well as the presence of a protein factor which regulates this activity.

Adenylyl Cyclases↗
PubMed1977

Adenylate cyclase from various dopaminergic areas of the brain and the action of loxapine.

The present report is a comparative study of adenylate cyclase activity in various areas of the brain identified as dopaminergic. Low levels of dopamine were found to stimulate adenylate cyclase from the striatum, median eminence, olfactory tubercle, nucleus accumbens and amygdala. Apomorphine, known to mimic the pharmacological and physiological effects of dopamine, stimulated adenylate cyclase from these areas. Several different classes of drugs effective in the treatment of schizophrenia were potent inhibitors of the stimulation by dopamine of the enzyme from these various regions. The drugs studied included representatives of the phenothiazine, butyrophenone, dibenzodiazepine and dibenzoxazepine classes. The inhibition by the dibenzoxazepine, loxapine, which is structurally very similar to the dibenzodiazepine, clozapine, was competitive with respect to dopamine. The calculated inhibition constant (Ki) for loxapine of about 15 nM was similar to that observed for some of the more potent phenothiazines. The results, considered together with previously published data, support the possibility that the therapeutic effects as well as the extrapyramidal and endocrinological side effects, of these antipsychotic agents may be attributable to their ability to block the activation of adenylate cyclase in various select areas of the brain.

Adenylyl Cyclase Inhibitors↗
PubMed1974

Dopamine-sensitive adenylate cyclase in mammalian brain: a possible site of action of antipsychotic drugs.

Adenylate cyclase (EC 4.6.1.1), selectively stimulated by low concentrations of dopamine, has been found in the olfactory tubercle, the nucleus accumbens, and the caudate nucleus of several mammalian species. Several different classes of drugs effective in the treatment of schizophrenia (antipsychotic drugs) were potent inhibitors of the stimulation by dopamine of the enzyme from these various regions. The drugs studied included representatives of the phenothiazine, butyrophenone, and dibenzodiazepine classes. The inhibition by these antipsychotic drugs was competitive with respect to dopamine. The most potent of the antipsychotic agents tested was fluphenazine, which had a calculated inhibition constant (K(i)) of about 5 x 10(-9) M. For each of several drugs tested, the K(i) for the enzyme from the olfactory tubercle was similar to that for the enzyme from the caudate nucleus. Several compounds closely related structurally to the psychoactive phenothiazines, but which have little or no antipsychotic or extrapyramidal actions clinically, had low relative potencies as inhibitors of dopamine-stimulated adenylate cyclase activity. The results, considered together with other data, raise the possibility that the therapeutic effects, as well as the extrapyramidal side effects, of these antipsychotic agents may be attributable, at least in part, to their ability to block the activation by dopamine of specific dopamine-sensitive adenylate cyclases in the human brain.

Adenylyl Cyclases↗