Dieldrin toxicity and in vivo incorporation of DL-(1-14 C)leucine.

The in vivo effect of a single oral dose (30mg/kg body weight) of dieldrin on proteolipid and phosphatidopeptide content of liver and brain and on total protein of liver, brain, plasma, muscle and kidney of rat was studied. Incorporation of (14C)leucine into total protein of liver was increased whereas labelling of total protein of muscle was decreased. Labelling of total protein of other tissues was unchanged. Incorporation into liver phosphatidopeptides was increased and this was consistent with an involvement of group. Proteolipid protein content of brain was increased and that of liver unchanged. There was, however, no change in the labelling of brain or liver proteolipids.     

In vivo incorporation of [14C]leucine into brain protein of mice treated with methylmercury and thiol complexes of methylmercury

The effect of methylmercury and thiol complexes of methylmercury on inhibition of protein synthesis was evaluated. Mice were injected (i.p.) with the following treatments: methylmercuric chloride, methylmercury-glutathione, methylmercury-cysteinylglycine and control (vehicle) for 10 days. Ten animals from each group were injected with [14C]leucine 90 min prior to death. The brains were removed and the extracted protein was subjected to liquid scintillation analysis. Mice receiving the methylmercury and methylmercury-glutathione treatments exhibited significantly greater weight loss than the control while the methylmercury-cysteinylglycine treatment was not significantly different than the control. Incorporation of [14C]leucine into brain protein was significantly depressed in the methylmercury (81% of control) and the methylmercury-glutathione (79% of control) treatments. Protein synthesis in mice receiving the methylmercury-cysteinylglycine complex although not significantly different than the methylmercury treatments was only 92% of the control mice.     

Covalent binding of [14C]methoxychlor metabolite(s) to rat liver microsomal components

[14C]Methoxychlor was incubated with NADPH-fortified liver microsomes from male rats, and covalent binding to microsomal components was determined. The binding process was markedly enhanced when microsomes from phenobarbital-treated rats were employed. However, when microsomes from methylcholanthrene-treated rats were used the level of binding was not significantly affected. Incubation in the presence of glutathione, cysteine, or ascorbate markedly diminished binding. Metyrapone and SKF 525-A, inhibitors of hepatic cytochrome P-450-linked monooxygenase activity, inhibited the binding. Also, ethylmorphine and hexobarbital, alternate substrates of the monooxygenase system, inhibited binding. There was no binding to microsomal components in the absence of NADPH or oxygen. TCPO (1,1,1-trichloropropane-2,3-oxide), an inhibitor of epoxide hydrase activity, failed to enhance the binding process. However, N,N'-diphenyl-p-phenylenediamine (NDP) and n-propyl gallate (PG), both free radical scavengers, decreased binding at micromolar concentrations without altering the extent of formation of polar [14C]methoxychlor metabolites. It was concluded that methoxychlor undergoes a hepatic microsomal monooxygenase(s)-mediated activation and that the resultant reactive metabolites (possibly free radicals) bind covalently to microsomal components. By contrast, the binding resulting from the incubation of an impure mixture of polar [14C]methoxychlor metabolites with liver microsomes did not require NADPH and O2 and was not affected by NDP, Pg, ascorbate, or heat-treatment of microsomes. This finding suggested that the binding subsequent to the initial metabolic activation of methoxychlor does not require further enzymatic transformation. However, whether the binding with metabolites represents the same chemical species as the binding with [14C]methoxychlor remains to be established.     

Interaction between glucose diet and ethanol on rat liver microsomal induction and liver plasma membrane damage in chronic hexachlorobenzene intoxication

Male Wistar rats fed for 60 days a glucose diet containing 17.5 mmol hexachlorobenzene/kg show a less pronounced increase in serum parameters and microsomal cytochrome P-450 concentration and a lower decrease in liver plasma membrane 5-nucleotidase, K⁺, Na⁺- and Mg⁺⁺-adenosine triphosphatase activities than the controls fed standard diet + hexachlorobenzene. Addition of 10% ethanol to the drinking water eliminates the glucose effect. The glucose diet and ethanol exert contrasting effects on microsomal enzyme induction and liver plasma membrane damage in hexachlorobenzene intoxication.Dedicated to Professor Dr. med. Herbert Remmer on the occasion of his 65th birthday     

Biochemical and pharmacological studies on amineptine (S 1694) and (+)-amphetamine in the rat

The pharmacological activities of amineptine (S 1694) and (+)-amphetamine and their interaction with biogenic amines have been examined in rats. The locomotor activity, stereotyped behaviour and hypothermia induced by amineptine were similar to but not as marked as those produced by (+)-amphetamine, and there was little or no anorectic action. Amineptine does not modify the concentrations of brain noradrenaline or acetylcholine which are respectively reduced and increased by (+)-amphetamine. Moreover, amineptine does not affect significantly the decrease of brain noradrenaline induced by an intraventricular injection of 6-hydroxydopamine, an effect significantly antagonized by (+)-amphetamine. On the other hand, like amphetamine, amineptine significantly reduces the effect of 6-hydroxydopamine on brain dopamine. Both drugs increase the striatal concentrations of homovanillic acid and show a cross tolerance in this action. Therefore they could act similarly on the striatal dopaminergine system. Amineptine thus appears to be a new type of antidepressant with a brain biochemical profile differing from that of other drugs used in depressive disorders.     

Biochemical and pharmacological studies on amineptine (S 1694) and (+)-amphetamine in the rat.

The pharmacological activities of amineptine (S 1694) and (+)-amphetamine and their interaction with biogenic amines have been examined in rats. The locomotor activity, stereotyped behaviour and hypothermia induced by amineptine were similar to but not as marked as those produced by (+)-amphetamine, and there was little or no anorectic action. Amineptine does not modify the concentrations of brain noradrenaline or acetylcholine which are respectively reduced and increased by (+)-amphetamine. Moreover, amineptine does not affect significantly the decrease of brain noradrenaline induced by an intraventricular injection of 6-hydroxydopamine, an effect significantly antagonized by (+)-amphetamine. On the other hand, like amphetamine, amineptine significantly reduces the effect of 6-hydroxy-dopamine on brain dopamine. Both drugs increase the striatal concentrations of homovanillic acid and show a cross tolerance in this action. Therefore they could act similarly on the striatal dopaminergine system. Amineptine thus appears to be a new type of antidepressant with a brain biochemical profile differing from that of other drugs used in depressive disorders.     

Interactions of (+)-amphetamine and chlorpromazine on neurones in the lower brain stem of the rat.

1 The ability of chlorpromazine to antagonize the effects of iontophoretic application of (+)-amphetamine to single neurones in the medulla and lower pons of anaesthetized rats has been studied. 2 Chlorpromazine, administered systemically or iontophoretically, consistently and specifically antagonized the excitatory actions of (+)-amphetamine, but not those of noradrenaline on the same neurone. 3 It is concluded that chlorpromazine reduces the effect of (+)-amphetamine by a presynaptic mechanism. 4 (+)-Amphetamine did not mimic the prolonged inhibitory response of some neurones to noradrenaline but often excited these neurones and chlorpromazine blocked these excitatory responses to (+)-amphetamine.     

ACTH and the stress-induced changes of lysine incorporation into brain and liver proteins.

When mice were subjected to footshock treatment and subsequently injected with [3H] lysine, the cerebral uptake of [3H] lysine, its incorporation into brain protein and the relative radioactivity (RR = protein radioactivity divided by amino acid radioactivity) were all increased. In the liver, footshocked mice showed decreased free lysine radioactivity, and increased protein radioactivity and relative radioactivity compared to quiet mice. The possibility that ACTH mediated these effects was investigated. The injection of saline had no effect in the brain but partially mimicked the footshock responses in the liver. Injections of ACTH 1--24 mimicked the effects of footshock in the brain, and further augmented the saline-induced effect on the RR in the liver. ACTH 4--10 increased the RR of brain protein, but produced no significant change in brain free lysine radioactivity or in any measure in the liver. Pretreatment of mice with the synthetic glucocorticoid, dexamethasone, did not enhance these effects and diminished the effect of ACTH 4--10 in the brain. ACTH treatment did not alter the profiles of brain polyribosomes. Lysine vasopressin, which is also released during stress, did not alter the incorporation of [3H] lysine into brain or liver protein, except at high doses when it decreased plasma radioactivity. These results suggest that secretion of ACTH at least partially mediates the stress-induced changes of [3H] lysine incorporation into brain and liver proteins, but that it is probably not the only factor involved.     

Irreversible binding of 14C from 14CCl4 to liver microsomal lipids and proteins from rats pretreated with compounds altering microsomal mixed-function oxygenase activity

¹⁴C from ¹⁴CCl₄ irreversibly binds to lipid and protein components of different liver subcellular fractions. Microsomal lipids bind more ¹⁴C than does either mitochondria or 105,000 g supernatant. The proteins from the 105,000 g fraction bind more ¹⁴C than those from the other two fractions. The extent of the irreversible binding of ¹⁴C to microsomal lipids and proteins is decreased by the prior treatment of the rats with cystamine, pyrazole, 3-methylcholanthrene or metopirone while it is increased by pretreatment with phenobarbital. The prior treatment with 2-diethylaminoethyl 2,2-diphenyl valerate hydrochloride (SKF 525A) increased the irreversible binding of ¹⁴C to microsomal lipids, but not to microsomal proteins. The results suggest that the irreversible binding of ¹⁴C to microsomal lipids is a more reliable expression of the CCl₄-activation step than the one to microsomal proteins. The ¹⁴CCl₃ free radicals responsible for the binding of ¹⁴C to lipid would arise during the reduction of the CCl₄/cytochrome P-450 complex mediated by cytochrome P-450 reductase.