Effect of ethanol dose on amino acid and urea concentrations in the fed rat liver in vivo

In order to assess the role of ethanol oxidation in vivo on amino acid metabolism and urea synthesis, the changes in the concentrations of hepatic dicarboxylic amino acids, glutamine, alanine, carbamoylphosphate and urea were measured in fed rats at various times after the administration of 10 and 50 mmoles of ethanol/kg body wt, i.p. (1) The dose dependence of the acute effects of ethanol upon liver dicarboxylic amino acids in vivo has been demonstrated. The 10 mmoles/kg ethanol dose determines an accumulation by 30 per cent of aspartate and glutamate in the rat liver (30 and 60 min after ethanol injection) whereas the 50 mmoles/kg ethanol dose induces a 35 per cent fall in the aspartate level at the same time, and only a 20 per cent increase in glutamate concentration during the second hour following ethanol injection. (2) The dose-dependent effects of ethanol upon the hepatic level of urea are also shown. A significant decrease by 20 per cent in the liver content of urea is only observed 60 min after the administration of the 50 mmoles/kg ethanol dose. (3) On the contrary, the ethanol induced alterations in the hepatic alanine and glutamine concentrations are not dose-dependent. A 50 per cent decrease in alanine level and a rise (about 30 per cent) in glutamine concentration are observed 30 and 60 min after the administration of the two ethanol doses. The comparison between the effects of either 10 or 50 mmoles/kg ethanol doses leads to the conclusion that the rate of ethanol oxidation related to the malate-aspartate shuttle activity is directly connected with the glutamate (and aspartate) concentration. These findings suggest that ethanol reduces the hepatic urea concentration in vivo only when the ethanol dose injected to rats induces a rapid decrease in the aspartate/glutamate ratio (about 40 per cent within 15 min following the injection of the 50 mmoles/kg ethanol dose).     

Metabolism of 3, 4-dihydroxyphenylalanine by isolated perfused rat liver

The metabolism of -3, 4-dihydroxyphenylalanine ( -dopa) and -dopa by the isolated perfused rat liver is described. After injection of 5 μc(192μg) -dopa-3-¹⁴C into the portal vein, the liver took up approximately one-third of the dose within 30 min. Blood cells of the perfusate (chiefly erythrocytes) took up one-fourth of the dose within 5 min; subsequently, most of this radioactivity was released back into plasma. -Dopa disappeared from plasma rapidly (half-life, approximately 30 min); after 2 hr of perfusion, less than 2 per cent of the dose could be recovered unmetabolized. Metabolites of dopa released from liver into bile accounted for up to 48 per cent of the dose and were chiefly glucuronides of N-acetyldopamine and N-acetyl-3-methoxydopamine. Major metabolites released into plasma were the glucuronides of 3-methoxy4-hydroxyphenylacetic acid and 3, 4-dihydroxyphenylacetic acid, the sulfate of N-acetyl-3-methoxydopamine, and 3-methoxy-4-hydroxyphenylalanine. Amines in plasma represented a minor fraction (less than 1 per cent of the dose) at all times during the perfusion. Norepinephrine and its metabolites were never detected. After injection of 5 μc -dopa-2-¹⁴C (32 or 192μg), less ¹⁴C was taken up by liver than when -dopa was used; similar amounts of ¹⁴C were taken up by the blood cells but were retained for the 5 hr of perfusion. -Dopa disappeared more slowly from plasma than -dopa; after 2 hr, 16 per cent of the dose was recovered unmetabolized. The metabolites of -dopa in bile (22 per cent of the dose) and in plasma were similar to those found when -dopa was substrate.     

Metabolism of 14C-2',3'-dideoxyinosine by the in situ perfused rat liver preparation

The metabolism and biliary excretion of 14C-dideoxyinosine (14C-ddI) has been investigated using the in situ perfused rat liver (PRL) preparation. After 2 h of perfusion through the liver, approximately 70-75 per cent of the total 14C-radiolabel was recovered in the perfusion medium, less than 1 per cent was excreted in bile and 15-18 per cent was retained in the liver. Hepatic clearance of ddI was 1.5 +/- 0.1 ml min-1 and half-life for the elimination of ddI from the medium was 22.9 +/- 2.0 min (n = 3). Hepatic extraction was estimated to be 7.5 per cent. HPLC analysis of the effluent perfusate indicated that ddI was metabolized to hypoxanthine, xanthine, uric acid, and to a polar metabolite which was tentatively identified as allantoin. Approximately 60-65 per cent of the ddI dose was converted to allantoin after 2 h of perfusion. Of the other three metabolites, uric acid levels increased to 20-30 per cent of the dose after 45 min and declined to about 5 per cent of the dose by the end of the perfusion period. Levels of hypoxanthine and xanthine were low and both compounds were not detected in the perfusate after 45 min post-infusion. In bile, the major peak, which accounted for about 50 per cent of the 14C-radiolabel co-eluted with the putative metabolite, allantoin (0.4 per cent of the dose). Uric acid (0.06 per cent of the dose) was the only other metabolite detected in bile. These results suggest that biliary excretion is a minor pathway for the elimination of ddI. Furthermore, ddI is rapidly cleared and metabolized by the liver to hypoxanthine, xanthine, uric acid, and to allantoin.     

Physiologic disposition of [3H]epinephrine in the rabbit fetus: Effect of promethazine

[³H]epinephrine was injected into fetal rabbits through the uterine wall on day 26 of gestation in order to study placental transfer, and the uptake, retention and metabolism of the hormone in fetal tissues. Less than 0.1 per cent of the administered [³H] was found in maternal blood or within uninjected littermates. Accumulation of [³H]/g of tissue was greatest in the fetal kidney, liver and intestine, and less in the heart and lung. Levels of [³H] in the fetal serum, heart, lung and placenta were comparable in value at 5 and 30 min, but all fell by 60 min. In contrast, the fetal kidney and intestine show a 2- to 4-fold accumulation of [³H] in 30 min as compared to 5 min, while the fetal liver exhibits a 10-fold accumulation over 30 and 60 min. [³H] metabolites present in fetal serum at 30 min, expressed as a per cent of the total radioactivity, are 45 per cent for metanephrine and 27 per cent for O-methylated deaminated products, while 25 per cent is present as unmetabolized [³H]epinephrine. O-methylated metabolites are predominant in the liver, where 85 per cent of the radioactivity comprises metanephrine in conjugated and unconjugated forms. Administration of promethazine to the doe prior to injection of [³H]epinephrine into rabbit fetuses resulted in a 40–64 per cent decrease in accumulation of [³H] in the fetal brain, liver, lung, kidney, intestine and heart. The pattern of metabolites in the serum of promethazine-treated fetuses shows an increase in the per cent of [³H] in the O-methylated, deaminated fraction from 27 to 37 per cent. While the total per cent of O-methylated metabolite is not altered in the liver of treated fetuses, metanephrine is predominantly present in the conjugated form. The liver of the rabbit fetus is an important site for accumulation of catecholamine metabolites and is pharmacologically sensitive to promethazine administered to the mother.     

Olivomycin-C14 distribution in the body of mice with Ehrlich's carcinoma resistant to the preparation]

Tests on mice with Ehrlich's carcinoma (solid and ascitic forms) evidenced that following a single intravenous injection of glycomycin-C14 its maximal concentrations are definable in 30 minutes--1 hour in the kidneys, liver, spleen and the blood (plasma). Six to seven percent of the total radioactivity of the tumor cells fell to the share of the nuclear fraction, while the rest of 93-94 per cent was made up by the remaining cellular components.     

Decrease in mouse lung and liver glutathione peroxidase activity and potentiation of the lethal effects of ozone and paraquat by the superoxide dismutase inhibitor diethyldithiocarbamate.

Intraperitoneal injection of mice with sodium diethyldithiocarbamate (1.2 g/kg), an inhibitor of superoxide dismutase, potentiated the lethal effects of ozone and of paraquat. Study of control mice injected with sodium diethyldithiocarbamate demonstrated an 80 per cent decrease in lung and liver superoxide dismutase activity in one hour, followed by a slow return towards normal. However, liver and lung glutathione peroxidase activites were also decreased, although to a lesser extent than superoxide dismutase, and the nadir was not observed until six hours and 30 min following injection. A decrease in liver non-protein sulfhydryl groups was also observed. Similarly, incubation of liver homogenale with diethyldithiocarbamate produced a marked loss in superoxide dismutase activity associated with a lesser, delayed decrease in gluthione peroxidase. The latter could be prevented by the addition of superoxide dismutase or by anaerobic conditions. Accordingly, the potentiation of the lethal effects of exogenous agents by diethyldithiocarbamate does not necessarily indicate a role for superoxide anion radical in the toxicity of these agents.     

Effectiveness of Antivenin (Crotalidae) Polyvalent following injection of Crotalus venom

Studies were done in rats to determine how long after the injection of a given amount of rattlesnake venom could antivenin be injected and afford protection. Protection was measured by neutralization of the lethal effect and by reduction of the local tissue effect. Eighty per cent of the rats receiving the antivenin at the time the venom was injected, survived, In the remaining 20 per cent survival time was increased approximately nine times. There was a complete absence of local tissue response. Rats receiving antivenin 10 min following the venom injection showed a survival rate of 60 per cent and survival time in the remaining rats was increased five-fold. Some localized tissue changes were observed. The rats receiving antivenin 20 min following venom injection showed a survival rate of 50 per cent, and survival time in the remaining animals was increased about 30 per cent. Rather severe localized tissue reactions were seen. The animals receiving antivenin 30 min following injection of the venom showed a survival rate of 33 per cent and a statistically insignificant increase in survival time. Severe localized tissue responses were seen. Rats receiving antivenin at 60 min showed no increase in survival time. The clinical significance of these data is discussed.     

Metabolism of 3-O-methyldopa by the isolated perfused rat liver

The disposition and metabolism of l-3-methoxy-4-hydroxyphenylalanine (3-O-methyldopa) in the isolated perfused rat liver system is described. When $\text{[}{}^{14}\text{C}\text{]3-O-}\text{methyldopa}$ (5 μCi, 1.9 mg, uniformly labeled except in the O-methyl carbon) was added to the perfusate, in the first 5 min the liver took up 10 per cent of the dose, and erythrocytes took up 30 per cent. After 5 min of perfusion, 3-O-methyldopa disappeared from plasma in a diphasic fashion; its half-life was 25 min between 5 min and 2 hr, and 360 min between 2 and 5 hr of perfusion. Cumulative excretion of radioactivity in bile accounted for 20 per cent of the dose. After 5 hr of perfusion, 35 per cent of the dose remained as unmetabolized 3-O-methyldopa (22 per cent in plasma, 8.5 per cent in erythrocytes, 3.4 per cent in liver and 1 per cent in bile). Known demethylated metabolites accounted for 6 per cent of the dose. The early appearance of 3,4-dihydroxyphenylalanine in erythrocytes, and its formation when the system lacked a liver, indicated that these cells were the site of demethylation. Free and conjugated 3-methoxy-4-hydroxyphenylacetic acid were major metabolites in the system. These compounds could have been metabolites of dopa. If this were so, demethylation of 3-O-methyldopa accounted for an additional 12.3 per cent of the dose. Transaminated metabolites (free and conjugated 3-methoxy-4-hydroxyphenyllactic acid) accounted for 19.0 per cent of the dose.     

Pharmacokinetics of 35S-tomizin in mice with leukemia L-1210

A comparative study of the distribution of 35S-tomisin in the organism of intact (without neoplasia) mice and those with L-1210 leucosis was carried out. In both animal groups the tagged drug was found to be largely accumulating early after its introduction in the tissues of the liver, kidneys, intestines, spleen and lymph nodes. In 30 minutes time following introduction of 35-S-tomison 7.3 +/- 0.7 per cent of its amount was detected in the ascitic fluid. On centrifugation of the tagged drug its bulk (92-95 per cent) remained in the supernatant fluid. During the first 24 hours the drug leaves the body: 25-35 per cent with urine, 3-5 per cent--with feces and 0.1-0.3 per cent--with bile. In the urine of mice with leucosis the products of the 35S-tomisin biotransformation appear earlier than in intact animals. The most marked immunodepressive effect of tomisin was marked with its administration 24 and 48 hours after immunization.     

Omega- and (omega-1)-hydroxylation of 4-chloropropionanilide by rabbits and rabbit liver microsomes

4-Chlorolactanilide, 4-chlorohydracrylanilide, 4-chloroglyceranilide, and 4-chloroglycolanilide were isolated from urine of rabbits injected with 4-chloropropionanilide. The product of (ω-1)-hydroxylation amounted to nearly 30 per cent of the dose and the ω-OH derivative to about 4 per cent. An average 91 per cent of the 4-chlorolactanilide was the l-(?)-isomer. After injection of dl-4-chlorolactanilide only a small shift was found in the ratio between l- and d-isomer of the 4-chlorolactanilide isolated from urine. Rabbit liver microsomes hydroxylated 4-chloropropion-anilide more rapidly in the (ω-1)-position than in the ω-position. Ninety-three per cent of the 4-chlorolactanilide isolated was the l-(?)-isomer. 4'-chloromandelanilide isolated from urine after injection of 4'-chlorophenylacetanilide was 94% l-(+)-isomer and methylphenylcarbinol isolated after injection of ethylbenzene was 75% d-(+)-isomer. As all optically active metabolites show the same relative configuration at the asymmetric center, only the configuration at the (ω-1)-C-atom determines the hydrogen which is replaced by a hydroxyl group, the rest of the molecule affecting only binding to the enzyme and rate of hydroxylation.     

Effects of pregnancy on the metabolism of drugs in the rat and rabbit

In rats 19–20 days pregnant, liver weight is increased by 40 per cent, cytochrome P-450 concentration is decreased by 25 per cent and the specific activities of 4-methylumbelliferone glucuronyl transferase and biphenyl-4-hydroxylase are reduced by 25 and 30 per cent, respectively; biphenyl-2-hydroxylase and p-nitrobenzoic acid reductase are not changed. In rats, 15–16 days pregnant, liver weight is increased by 33 per cent but the concentration of cytochrome P-450 and the specific activities of the drug microsomal enzymes are unchanged. Expressed as total amounts per whole liver, there is an increase in microsomal protein and nitro-reductase in both 15–16 and 19–20 day pregnant animals but no changes occur in cytochrome P-450, glucuronyl transferase or biphenyl hydroxylases.Hexobarbital administered to rats at doses related to pregnant body weight increases the sleeping-time from 50 min in non-pregnant animals to 110 min at full-term, but when administered on the basis of the non-pregnant body weight the duration of anaesthesia remains unchanged.Pretreatment of pregnant (19–20 days) and non-pregnant rats with phenobarbital leads to similar increases in microsomal protein (25 per cent) and nitroreductase activity (40 per cent); cytochrome P-450 is increased in non-pregnant animals (30 per cent) but not in the pregnant, although biphenyl-4-hydroxylase is increased in both to such extents as to annul the inhibitory effect of pregnancy. Pretreatment with methylcholanthrene gives rise to similar increases in cytochrome P-450 (30 per cent) and biphenyl-2-hydroxylase (10-fold increase) in both pregnant and non-pregnant rats and again increases biphenyl-4-hydroxylase so as to annul the effect of pregnancy.With rabbits, no change occurs in liver weight, microsomal protein, nitro-reductase, cytochrome P-450, or biphenyl-4-hydroxylase at full-term pregnancy, but glucuronyl transferase is reduced by 20 per cent, and coumarin-7-hydroxylase by 60 per cent. Pretreatment of rabbits with phenobarbital increases microsomal protein (15, 25 per cent), nitro-reductase (70, 80 per cent), cytochrome P-450 (130, 90 per cent), biphenyl-4- hydroxylase (50, 60 per cent), coumarin-7-hydroxylase (40, 150 per cent), and glucuronyl transferase (65, 15 per cent) in both non-pregnant and pregnant animals, respectively.The decrease during pregnancy of hepatic glucuronyl transferase is attributed to competitive inhibition by high levels of endogenous estrogenic and progestational steroids, but the decrease in the activities of the microsomal hydroxylating enzymes is attributed to the decrease in P-450, which may result from high levels of growth factors.     

Interaction of glycine with ethanol

It has been suggested by Blum et al. [Science, N.Y.176, 292 (1972)] that the enhancement of the ethanol sleep time by glycine in mice was due to an interaction of these compounds in the central nervous system. We have measured glycine levels in C57BL/6J mice after an ethanol injection (4 g/kg, i.p.) and found no significant alterations of glycine levels in four brain regions at 15, 45, 90 and 150 min after injection. An exception was in the medulla at 150min, where a significant decrease (12 per cent) of glycine level was observed. The simultaneous injection of glycine (9 m-moles/kg) and ethanol (4 g/kg) resulted in a significant prolongation of the sleep onset time and a 20 per cent increase in the sleep time over controls, which were injected with saline-ethanol. When the same dose of glycine was administered 30 min before the ethanol injection, there was no significant change in the sleep duration but there was a prolongation of the sleep onset time. Plasma glycine levels were higher in mice injected simultaneously with glycine-ethanol than in those injected with glycine-saline. Brain glycine levels were only slightly elevated but not significantly different in these two groups. Gamma-aminobutyric acid (GABA) levels in the brain regions were not increased after glycine injection. The data indicate that the degree of interaction between glycine and ethanol was minimal, and that such an interaction was not a result of an alteration of the rate of ethanol metabolism. It was also unlikely to be a result of a glycine-induced elevation of GABA in the brain, as suggested by Blum et al.     

Biotransformation of 4-dimethylaminophenol in the dog

4-Dimethylaminophenol (DMAP), after an i.v. injection, quickly forms ferrihemoglobin by catalytic transfer of electrons from ferrohemoglobin to oxygen. This reaction is rapidly terminated by covalent binding of oxidized DMAP to the reactive SH-groups of hemoglobin and to reduced glutathione within the red cells, and by conjugation with glucuronic or sulfuric acid presumably in the liver. Fifteen min after i.v. injection of DMAP, 3.25 $\text{mg}\text{kg}$, ¹⁴C-labeled in the ring, no intact DMAP was detected in the blood. The concentrations of metabolites in the blood were as follows: 33 μM DMAP covalently bound to hemoglobin. 30 μM S,S,S-(2-dimethylamino-5-hydroxy-1,3,4-phenylene)-Tris-glutathione (Tris-IGS)-DMAP) 90 per cent of it located within the red cells, 5 μM DMAP-glucuronide, and 22 μM DMAP-sulfate. Within 3 days, 90 per cent of the radioactivity was excreted in the urine, 4 per cent in the faeces. In the 24 hr urine, 25 per cent of the DMAP injected was excreted as DMAP-sulfate, 15 per cent as DMAP-glucuronide, and 23 per cent as DMAP-thioethers, mainly as S,S,S-(dimethylamino-5-hydroxy-1,3,4-phenylene)-Tris-cysteine. When DMAP, ¹⁴C-labeled in the methyl groups, was administered 11 per cent of the radioactivity was excreted in the urine as dimethylamine. It is concluded that most of the thioethers found in the urine derived from Tris-(GS)-DMAP which had been produced within the red cells indicating an important role of the red cells on biotransformation of DMAP.     

Further evidence of cyclic AMP-mediated hypertrophy as a prerequisite of drug-specific enzyme induction.

We have previously reported that the administration of phenobarbital, 3-methylcholanthrene or the polychlorinated biphenyl, Aroclor-1254, to rats resulted in an early and sequential increase in the activities of hepatic cAMP-dependent protein kinase(s), omithine decarboxylase and RNA polymerase I. It was suggested that this sequence of events was involved in both liver hypertrophy and the induction of microsomal mixed-function oxygenases. To further test this hypothesis, we investigated if mice unable to induce aryl hydrocarbon hydroxylase in response to 3-methylcholanthrene exhibited increases in these cAMP-mediated events. A single dose of 3-methylcholanthrene (150 mg/kg, i.p.) was administered to male C57B1/6J (aryl hydrocarbon responsive) and DBA/2J (aryl hydrocarbon nonresponsive) mice. In the C57B1/6J mice, the hepatic cAMP concentration increased to 165 per cent of control within 1 hr. Maximal increases in the activities of liver cAMP-dependent protein kinase(s) (160 per cent), ornithine decarboxylase (210 per cent) and RNA polymerase I (120 per cent) occurred at 2, 4 and 6 hr, respectively, in the responsive mice. There were no detectable increases in any of these parameters in the nonresponsive (DBA/2J) mice. Multiple doses of 3-methylcholanthrene (20 mg/kg, i.p., daily × 3) resulted in increases in hepatic aryl hydrocarbon hydroxylase (460 per cent) and liver weight/body weight ratios (118 per cent) in the responsive (C57B1/6J) mice killed at 5 days. There was no increase in either of these parameters in the nonresponsive (DBA/2J) mice. Both the responsive and nonresponsive mice responded similarly to a single parental dose of phenobarbital (100 mg/kg) with maximal increases in the activities of cAMP-dependent protein kinase(s) (150 per cent), ornithine decarboxylase (160 per cent) and RNA polymerase I (135 per cent) at 2, 4 and 8 hr respectively. Multiple doses of phenobarbital (100 mg/kg, i.p., daily × 3) resulted in increased ethylmorphine N-demethylase activity (160 per cent) and liver weight/body weight ratios (130 per cent) in both strains of mice at 5 days. These data provide further evidence of coupled cAMP-mediated hypertrophy and induction of mixed-function oxygenases in liver.     

Metabolism of [3H]epinephrine in rabbit fetal tissues

[³H]epinephrine was injected into rabbit fetuses through the uterine wall on day 26 of gestation and its metabolism was studied in fetal tissues. [¹⁴C]metanephrine (MN) was synthesized using a soluble rat liver preparation and it, along with [¹⁴C]epinephrine, was used as recovery markers for the quantitation of metabolites of [³H]epinephrine. The radiochemical purity of MN, the predominant metabolite isolated from the fetal liver, was achieved by obtaining a constant [³H]/[¹⁴C] after sequential thin-layer chromatography. Thirty min after the injection of labeled hormone. [³H]epinephrine comprised 25 per cent of the radioactivity in the serum and 30 per cent in the heart, while less than 5 per cent was found in the lung, liver, kidney and intestine. Unconjugated MN comprised 45 per cent of the [³H] in the serum, 63 per cent in the heart and lung and 47, 46 and 40 per cent in the liver, kidney and intestine respectively. Conjugated MN is only found in liver, kidney and intestine and accounts for 35–40 per cent of the tissue radioactivity. Enzymatic hydrolysis of conjugates with β-glucuronidase in the presence and absence of sulfatase indicates that MN is present as a glucuronide conjugate. O-methylated, deaminated metabolites accounted for 27 per cent of the radioactivity in the serum, 28 per cent in the lung and between 7 and 16 per cent in the heart, liver, kidney and intestine. Thus, in the fetal rabbit, O-methylation is the predominant route of metabolism of injected [³H]epinephrine, followed by extensive glucuronide conjugation in the fetal liver, kidney and intestine.     

Pharmacokinetics and pharmacodynamics of physostigmine in the rat after oral administration

The distribution, metabolism, and pharmacokinetics of physostigmine (Phy) and the time course of butyrylcholinesterase (BuChE) in plasma and cholinesterase (ChE) activity in brain and muscle and their relationship to Phy concentration were described after oral administration of 3H-Phy (650 micrograms kg-1) to rats. Physostigmine concentration vs time data was analyzed by nonlinear computer fitting program using one-compartment model. The absorption rate constant (ka) and elimination rate constant (ke) were found to be 0.1 +/- 0.07 min-1 and 0.036 +/- 0.024 min-1, respectively. Cpmax and tmax were 3.3 ng ml-1 and 16 min. The clearance (C1) was found to be 80.9 ml min-1kg-1. Half-life of Phy in brain, muscle, and liver were 33.4 min, 22.5, and 28 min, respectively. The bioavailability (F) was calculated to be 0.02 and the extraction ratio was found to be 0.98 indicating the 'first pass' effect. Butyrylcholinesterase activity in plasma was 76 per cent at 15 min and this activity did not change significantly up to 120 min. However, Phy concentration in plasma was very low; 2.89 ng ml-1 at 15 min and declined to 0.71 ng ml-1 at 90 min. Physostigmine concentration in brain peaked at 22 min to 2.85 +/- 1.09 ng g-1 and declined to 0.33 +/- 0.11 ng g-1 at 60 min. Cholinesterase activity in brain was 96 per cent, 82 per cent and 89 per cent at 10, 45, and 120 min, respectively. Physostigmine concentration in muscle was very low and the ChE activity in the muscle was 66.4 per cent of control at 45 min. The time course of Phy metabolism indicated that at 5 min most of the RA in the tissues was due to metabolites accounting for 94.6 per cent in plasma, 90 per cent in liver, 79.8 per cent in brain and 86.3 per cent in muscle. M1 appeared to be the major metabolite followed by eseroline. The results showed extremely low concentrations of Phy (200 times less in plasma and 350 times less in brain) after oral administration compared to our previous studies with the same dose after i.m. administration.     

Intramuscular administration of atropine in the rat: jet spray versus conventional needle injection

The characteristics of atropine plasma levels after jet spray injection were compared to those after conventional needle injection (i.m.) in 12 male rats, six per group. Blood samples were sequentially collected from the tip of the tail over a 7h period. Injection of atropine sulfate (8.0 mg kg-1) using the jet spray resulted in mean peak plasma levels of 650 ng ml-1 (95 per cent C.I. = 90) compared to 488 ng mg-1 (95 per cent C.I. = 64) using a conventional needle. Times to reach maximum concentration were 30 min (95 per cent C.I. = 12) and 58 min (95 per cent C.I. = 6) for the jet spray and needle, respectively. Histopathologic examination (5 days post-injection) of target muscle showed that minimal fiber damage resulted from using the low pressure setting on the jet spray. The results suggest that the jet spray may offer a means of increasing the antidotal benefit over that achieved with conventional techniques using presently available therapeutic formulations for acetylcholinesterase poisoning.     

Distribution of Microcystis aeruginosa Peptide Toxin and Interactions with Hepatic Microsomes in Mice

Abstract: Purified ¹⁴C-labelled peptide toxin from the cyanobacterium Microcystis aeruginosa was administered intraperitoneally to mice and the distribution of label determined between the major organs. Seventy per cent of the label was localized in the liver after 1 min.; this value increasing to almost 90 per cent after 3 hours. Label associated with the lungs and other individual organs varied between 10 and 1 per cent of the ¹⁴C recovered throughout. Three microsomal enzyme inducers, β-naphthoflavone, 3-methylcholanthrene and phenobarbital, afforded protection against liver damage and extended survival if given to mice before the administration of an LD50 dose of toxin. Toxin-dependent changes in liver cytochrome levels were also reduced by the enzyme inducers.     

Cocaine-induced hepatic necrosis in mice--the role of cocaine metabolism.

Liver damage following cocaine injection in mice is due to the action of a metabolite of cocaine rather than of cocaine itself. The bioactivation of cocaine to a toxic metabolite appears to be a multi-step process, and is carried out by the cytochrome P-450 microsomal mixed function oxidase system. Inhibitors and inducers of this system blocked or potentiated liver damage respectively. Norcocaine was found to be more potent than cocaine, but also required further metabolism for hepatotoxicity. Inhibition of esterase activity increased damage from both cocaine and norcocainee. Most metabolites and analogues of cocaine were not hepatotoxic, indicating fairly strict structure requirements for activation. N-Hydroxynorcocaine, a possible metabolite of norcocaine, was also hepatotoxic. However, it too required further metabolism in order to produce liver damage. Glutathione in the liver was depleted after cocaine or norcocaine by 25–30 per cent at 1 hr after injection. Cysteine pretreatment offered protection from cocaine. These results suggest that an active metabolite of N-hydroxynorcocaine may be responsible for the liver damage observed after injection of cocaine into mice.     

Egg albumin microspheres containing sulphamethizole

Egg albumin microspheres containing sulphamethizole have been prepared by a capillary extrusion procedure. The microspheres were coarse (dvn = 1835 microns) with a narrow size distribution and tended to lose their spherical shape on drying. Scanning electron microscopy revealed that the microspheres were porous with drug concentrated at the periphery of the matrix. This excess surface concentration resulted in a burst effect for drug release in acidic dissolution media with up to 30 per cent drug released in 2 min. This was followed by a more gradual release of drug and finally the release tended to tail off as the matrix became depleted of drug. The average t50 per cent release was 12 min. Variable swelling of the matrix occurred during the first 20-30 min of dissolution which complicated the interpretation of release data. Treatment of the albumin spheres with spermaceti or paraffin wax tended to reduce swelling and increased the t50 per cent release to 33 min and 43 min respectively. Cross-linking of the matrix with aldehydes or by gamma-irradiation proved unsatisfactory.