Central and peripheral effects of serotonin on the immobility response in chickens

The effects of low and high doses of serotonin on tonic immobility (TI) duration and susceptibility in 10- and 45-day-old chickens were examined. High doses of serotonin reduced the number of inductions required to produce TI, regardless of the subject's age. In contrast, low and high doses of serotonin produced biphasic increases and decreases in TI duration in 10-day-old birds, but there were no apparent effects on immobility duration by either dose of this drug in older chickens. These results are discussed in terms of the formation of the blood-brain barrier in domestic fowl and the differential peripheral versus central actions by serotonin on TI susceptibility and response duration.     

Development of diltiazem deacetylase and demethylase activities during ontogeny in rabbit.

1. Diltiazem (DTZ) undergoes extensive metabolism in hepatic and extrahepatic tissues. Deacetyldiltiazem (M1) and N-desmethyldiltiazem (MA) are two of the main basic metabolites of DTZ that retain pharmacological activity. The development of DTZ deacetylase and demethylase activities through ontogeny has not been addressed. In order to address this issue, in vitro studies have been carried out using the blood and several tissues of rabbit as enzyme sources. In addition, in vivo studies using a pharmacokinetic approach were carried out to support the in vitro findings. 2. DTZ was incubated with homogenates of selected tissues and in whole blood and DTZ, and its metabolites were assayed by HPLC. In addition, a pharmacokinetic study after intraperitoneal administration of DTZ in the 1-, 8-, 16-, 30-day-old and adult rabbit were also carried out. 3. DTZ deactylase activity was detected whatever the age and tissue examined (including blood). Except in gut homogenates, this activity was shown to be higher at earlier postnatal ages. DTZ demethylase activity was only detected in the liver and gut homogenates and in whole blood. This activity increases from the 1- to 30-day-old rabbit (except for blood), after which it decreases slightly to reach the adult level. 4. In vivo experiments showed a close pharmacokinetic profile throughout ontogeny (except for the 30-day-old rabbit) after DTZ intraperitoneal administration. 5. Extrahepatic metabolism may play a more significant role in the overall metabolism and pharmacokinetics of DTZ at earlier stages of development. 6. Finally, in vivo studies Suggest that age does not seem to modify DTZ disposition and, for this reason, dosage may not have to be taken into account as a function of age.     

Excessive accumulation of hepatic copper in LEC rats aged 80 days without hepatitis and 130 days with hepatitis.

The Cu concentration was about 40 and 60 times higher in the liver in Long-Evans with a cinnamon-like coat color (LEC) rats aged 80 days (without hepatitis) and 130 days (with hepatitis), respectively than in the liver in Fischer rats. Most hepatic Cu was recovered in the cytosol fraction. Furthermore, about 96% and 84% of the cytosolic Cu was found in the metallothionein region on a Sephadex G-75 column in LEC rats aged 80 and 130 days, respectively. The hepatic metallothionein concentration was about 130 to 140 times higher in LEC rats than in Fischer rats when the concentration was expressed as metallothionein-bound Cu. Three forms of Cu-metallothionein were isolated by DEAE-cartridge. Although the concentration of hepatic Cu-metallothionein and its composition of polymorphic form were not changed greatly in hepatitis phase (in the 130-day-old LEC rats), activities of serum enzymes, aspartate aminotransferase (GOT) and alanine aminotransferase (GPT) were increased significantly. The LEC rat showed a significantly low concentration of biliary Cu and markedly low activity of ceruloplasmin (as ferroxidase). Serum Cu showed a low concentration in the 80-day-old LEC rats, but recovered to the control level in the 130-day-old LEC rats. The abnormal accumulation of Cu may be due to the inherent reduction of excretion of Cu into the bile and blood. Such deposition may be a trigger for the onset of the spontaneous hepatitis occurring at 90-120 days after birth and for the onset of hepatoma later.     

Excessive Accumulation of Hepatic Copper in LEC Rats Aged 80 Days without Hepatitis and 130 Days with Hepatitis

Abstract: The Cu concentration was about 40 and 60 times higher in the liver in Long-Evans with a cinnamon-like coat color (LEC) rats aged 80 days (without hepatitis) and 130 days (with hepatitis), respectively than in the liver in Fischer rats. Most hepatic Cu was recovered in the cytosol fraction. Furthermore, about 96% and 84% of the cytosolic Cu was found in the metallothionein region on a Sephadex G-75 column in LEC rats aged 80 and 130 days, respectively. The hepatic metallothionein concentration was about 130 to 140 times higher in LEC rats than in Fischer rats when the concentration was expressed as metallothionein-bound Cu. Three forms of Cu-metallothionein were isolated by DEAE-cartridge. Although the concentration of hepatic Cu-metallothionein and its composition of polymorphic form were not changed greatly in hepatitis phase (in the 130-day-old LEC rats), activities of serum enzymes, aspartate aminotransferase (GOT) and alanine aminotransferase (GPT) were increased significantly. The LEC rat showed a significantly low concentration of biliary Cu and markedly low activity of ceruloplasmin (as ferroxidase). Serum Cu showed a low concentration in the 80-day-old LEC rats, but recovered to the control level in the 130-day-old LEC rats. The abnormal accumulation of Cu may be due to the inherent reduction of excretion of Cu into the bile and blood. Such deposition may be a trigger for the onset of the spontaneous hepatitis occurring at 90-120 days after birth and for the onset of hepatoma later.     

Alkyltin inhibition of ATPase activities in tissue homogenates and subcellular fractions from adult and neonatal rats

Inhibition of ATPase activities by triethyltin (TET), diethyltin (DET), monoethyltin (MET), and trimethyltin (TMT) was studied in homogenates of brain and liver from adult and neonatal rats. In the adult, sensitivities were as follows: mitochondrial ATPase of liver much greater than Na+, K+-ATPase of brain approximately equal to mitochondrial ATPase of brain greater than nonspecific ATPase of brain and liver. MET did not produce significant inhibition. ATPase activities in brain and liver homogenates from TET-treated adult rats did not differ from controls. Mitochondrial ATPase in brain homogenates from 5-day-old rats was two orders of magnitude more sensitive to TET than brain homogenates from adult rats (IC50 of 2.5 microM in the 5-day-old neonate vs 260 microM in the adult). By contrast, isolated mitochondria and synaptosomal fractions from adult and neonatal brains were equally sensitive to TET (IC50 = 1-3 microM). At 10 days of age, following the onset of myelination, the IC50 for TET inhibition of brain mitochondrial ATPase increased to 71 microM. Myelin added directly to isolated mitochondria also reduced TET-induced inhibition. It is concluded that in vivo brain tin concentrations in 5-day-old rats following a neurotoxic dose of TET are sufficient to inhibit brain mitochondrial ATPase, whereas in adults, tin concentrations are insufficient for inhibition. In the adult rat, TET binding to myelin appears to prevent inhibition of brain mitochondrial ATPase, and the target of toxic action may be myelin. In the neonateal rat, TET may inhibit oxidative phosphorylation in unmyelinated brain tissue, leading to neuronal cell death.     

Altered diltiazem metabolism in the neonatal rabbit following intra-uterine chronic exposure to diltiazem

1. Diltiazem undergoes extensive metabolism in hepatic and extrahepatic tissues. Deacetyldiltiazem (M1) and N-demethyldiltiazem (MA) are two of the main basic metabolites of diltiazem that retain pharmacological activity. This drug impairs its own metabolism after chronic administration in the adult patient. The study examines the possibility that intra-uterine exposure following chronic maternal therapy with DTZ from mid-gestation to term also impairs DTZ metabolism of its offspring. 2. DTZ was incubated in homogenates from liver, lung, brain and gut and in the whole blood of animals whose mothers were exposed to chronic treatment with diltiazem or unexposed (placebo). DTZ and its metabolites were assayed by HPLC. 3. DTZ deacetylase activity observed in liver, lung and brain homogenates from 1-, 8- and 16-day-old rabbits was significant lower in exposed animals. In gut homogenates, this age-dependent effect was not so clear. This inhibition could not be detected in any organ of 30-day-old rabbits. On the other hand, the activity observed in whole blood was not altered by intra-uterine chronic exposure to DTZ. 4. DTZ demethylase activity showed no differences in tissue homogenates and in whole blood from exposed compared with the unexposed rabbit. 5. In conclusion, the findings suggest that intra-uterine chronic exposure to DTZ has a large and prolonged effect on newborn metabolism deacetylase activity compared with the unexposed rabbit.     

Age-related morphometric differences in responses of rat lungs to ozone

The influence of age on morphologic changes in lungs of rats exposed to ozone was studied in female Sprague-Dawley rats, aged 60 and 444 days. Rats of both age groups were exposed continuously for 72 hr to either 0.35 or 0.80 ppm ozone, or to filtered air. Tissues were evaluated using light microscopic morphometry and scanning electron microscopy. The lungs from ozone-exposed 60-day-old rats had larger volume fractions of centriacinar lesions than lungs from exposed 444-day-old rats. Within each age group there was an observed dose response, with rats exposed to 0.80 ppm ozone having larger volume fractions of lesions than those exposed to 0.35 ppm. Only the 444-day-old rats lost body weight during the exposure period. They also had smaller fixed lung volumes than same-aged controls. All 60-day-old rats gained weight during the exposure period, although rats exposed to 0.80 ppm ozone gained less than filtered air controls. Lesions observed in both age groups of female rats were qualitatively similar to those previously described in young adult male rats. We conclude that there are age-related differences in the morphometric responses of rats to ozone exposure. Younger rats had larger proportions of centriacinar lesions and macrophages while older rats had greater body weight and lung volume changes.     

Altered diltiazem metabolism in the neonatal rabbit following intra-uterine chronic exposure to diltiazem

1. Diltiazem undergoes extensive metabolism in hepatic and extrahepatic tissues. Deacetyldiltiazem (M1) and N-demethyldiltiazem (MA) are two of the main basic metabolites of diltiazem that retain pharmacological activity. This drug impairs its own metabolism after chronic administration in the adult patient. The study examines the possibility that intra-uterine exposure following chronic maternal therapy with DTZ from mid-gestation to term also impairs DTZ metabolism of its offspring. 2. DTZ was incubated in homogenates from liver, lung, brain and gut and in the whole blood of animals whose mothers were exposed to chronic treatment with diltiazem or unexposed (placebo). DTZ and its metabolites were assayed by HPLC. 3. DTZ deacetylase activity observed in liver, lung and brain homogenates from 1-, 8- and 16-day-old rabbits was significant lower in exposed animals. In gut homogenates, this age-dependent effect was not so clear. This inhibition could not be detected in any organ of 30-day-old rabbits. On the other hand, the activity observed in whole blood was not altered by intra-uterine chronic exposure to DTZ. 4. DTZ demethylase activity showed no differences in tissue homogenates and in whole blood from exposed compared with the unexposed rabbit. 5. In conclusion, the findings suggest that intra-uterine chronic exposure to DTZ has a large and prolonged effect on newborn metabolism deacetylase activity compared with the unexposed rabbit.     

Effects of rubratoxin and aflatoxin on oxygen consumption of Krebs cycle intermediates

The in vitro and in vivo effects of rubratoxin B and aflatoxin B₁ were examined using whole homogenates and mitochondria from livers of various animal species. At a concentration of 3.28 × 10^?4m, rubratoxin inhibited, in mice, the in vitro oxygen uptake of Krebs cycle intermediates, particularly citrate and succinate. Inhibition was greater in males. Inhibition of oxygen uptake in brain and ileum homogenates was greater than in liver homogenates. Succinate was the only Krebs cycle intermediate inhibited by rubratoxin to a greater extent in vitro than in vivo. A varied species susceptibility to poisoning by rubratoxin also was observed.Aflatoxin inhibited oxygen uptake in vivo but not in vitro in all species examined except weanling rats. Rubratoxin was the inhibitory agent in in vitro mixtures of rubratoxin B and aflatoxin B₁. Neither mycotoxin had an in vitro effect on P/O ratios or on glycolysis in liver homogenates from male mice.     

A CONTROLLED STUDY OF THE EFFECTS OF AEROBIC EXERCISE ON ANTIHYPERTENSIVE DRUG REQUIREMENTS OF ESSENTIAL HYPERTENSIVE PATIENTS IN THE GENERAL PRACTICE SETTING

1. To investigate the effect of an exercise training programme on antihypertensive drug requirements, 19 sedentary subjects (14 men and five women) with mild essential hypertension (systolic blood pressure greater than 140 mmHg but less than 180 mmHg), aged 29-55 years, were randomly assigned to 16 weeks of moderate intensity exercise or light intensity exercise (control), and titrated on antihypertensive drug therapy (captopril and hydrochlorothiazide) until resting systolic blood pressure (sitting) of less than 140 mmHg was achieved. 2. The moderate exercise group (n = 11) followed a graded walk-jog programme to greater than 60% age-predicted maximum heart rate (HRmax), attending 45 min sessions, three times each week. The light exercise group (n = 8) followed a programme of flexibility (stretching exercises) and walking to less than 60% age-predicted HRmax, attending 45 min sessions, three times each week. 3. There was no difference between treatment groups for the level of reduction in both resting systolic and diastolic blood pressure over the 16 weeks (15.64 +/- 10.6/12.81 +/- 9.97 mmHg in the moderate intensity group and 15.31 +/- 10.9/7.7 +/- 7.1 mmHg in the light intensity group). The change in 24 h ambulatory blood pressure profile was also similar in both treatment groups. The final antihypertensive drug requirements to achieve these changes in blood pressure was not significantly different between the two treatment groups. This was despite a significant improvement in submaximal exercise performance in the moderate intensity exercise group (P less than 0.001). 4.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibition of brain cation pump enzyme by in vitro lead ion: effects of low level [Pb] and modulation by homogenate

Rat brain homogenates were preincubated with lead chloride for 20 min at 0 degrees C. Inhibition of K-pnitrophenylphosphatase (K-pNPPase), which measures the dephosphorylation step of Na,K-ATPase, reached steady state within 10 min and was readily reversible. The activity in brain, homogenates prepared from 60-day-old rats, expressed (mean +/- SE) as a percentage of control (100.0 +/- 0.48%), fell to 89.4 +/- 0.52% at 0.25 microM [Pb] to 64.2 +/- 1.65% at 5 microM [Pb]. However, between 5 and 25 microM [Pb] K-pNPPase activity significantly increased (to 85.4 +/- 3.14% at 25 microM) before it again fell above 30 microM. Similar results were obtained with brain homogenates prepared from 10-day-old rats. The multiphasic nature of this dose-response curve did not change with changes in buffer, substrate, anion, test tube order, or test tube composition (glass vs plastic), and appeared to be intrinsic to homogenate-Pb interactions. Microsomal preparations also exhibited multiphasicity, but with a shift in the inflection points. However, there was no multiphasicity with commercial hog brain Na,K-ATPase, suggesting an interaction between a component in the rat brain preparations and lead ion. Addition of boiled rat brain homogenate to commercial Na,K-ATPase resulted in partial protection from lead inhibition but did not produce multiphasicity over the ranges tested. Bovine serum albumin provided less protection. We conclude that there is a complex interaction among K-pNPPase activity, some factor in the rat brain homogenate, and low levels of lead ion.     

Delayed neurotoxicity of triphenyl phosphite in hens: Pharmacokinetic and biochemical studies

The organophosphorus compound, triphenyl phosphite (TPP), caused ataxia in chickens 8-14 days after single po or iv administration. The po and iv ED50 values were 1414 and 35.4 mg/kg, respectively. Chickens which developed ataxia lost 14.4 +/- 2.5% (mean +/- SEM, n = 14) of their initial weight at 28 days and the paralyzed birds showed a severe reduction of 29.3 +/- 2.9% (n = 13) of their initial weight at death or at 28 days after dosing. For the first 4-hr interval after iv injection of 50 mg/kg, the elimination of TPP from plasma consisted of at least two exponential phases; the half-lives of the first and second phases were approximately 30 and 60 min, respectively. When the birds received 100 mg/kg (iv) fatty tissue showed the highest TPP concentration, e.g., 215 micrograms/g fresh wt at 6 hr postdosing. The half-life was approximately 24 hr. Among neural tissues, the sciatic nerve had the highest concentration, followed by the spinal cord, the cerebellum, and the cerebrum. The red muscles, such as adductor magnus, contained about 4-30 times as much TPP as did the white muscles, such as biceps brachii, 6 hr after treatment. Time course effects of TPP treatment on mitochondrial enzymes in leg skeletal muscles were examined by treating hens with 50 mg/kg (iv) and euthanizing the birds at 6 hr to 8 days postdosing. The creatine kinase (CK) activities of the adductor and the soleus were significantly decreased at 2 (48 hr), 4, and 8 days, and at 4 and 8 days postdosing, respectively. Adductor magnus and soleus succinate dehydrogenase (SDH) activities were decreased markedly at 24 and 48 hr, and at 2 (48 hr), 4, and 8 days, respectively. Cytochrome oxidase (COD) activity in adductor magnus and soleus did not decrease during the time course. Biceps femoris CK, SDH, and COD activities were not affected by TPP treatment at this dosage. These results suggest that TPP administration affects the mitochondrial metabolism in skeletal muscle, especially red muscle of chickens.     

The influence of silybin from Silybum marianum (L.) Gaertn. on in vitro phosphatidyl choline biosynthesis in rat livers

In rat livers, removed 60 min after i.p. application of 150.6 mg/kg silybin-dihemisuccinate-di-Na-salt, in vitro incorporation of choline-(methyl-14C) into phosphatidyl choline by the postmitochondrial fraction of liver homogenates was enhanced in comparison with controls. These results are associated with increased activities of CTP-choline-phosphate cytidyltransferase. Enzyme activities were also enhanced after addition of 7.5 x 10(-6) mol/l silybin to incubation mixtures obtained from untreated rats.     

Study of ochratoxin A (OTA)-induced oxidative stress markers in broiler chicks

The current study was designed to investigate the effects of ochratoxin A (OTA) on the oxidative stress in day-old broiler chicks. A total of 60-day-old broiler chicks were divided into four equal groups A–D. Group A was control, groups B–D were administered with different levels of OTA (1.6, 3.2 and 6.4?mg/kg of feed), respectively, for 10?days from day one of their age. Superoxide dismutase (SOD), glutathione peroxidase (GPx) and total antioxidant status of blood plasma, RBCs hemolysate and supernatant of tissue homogenates (liver, kidney and muscles) were estimated in all groups on days 11 and 31 in order to determine the oxidative stress in chicks. The results revealed a significant dose-dependent decrease in the SOD, GPx and TAS levels in all OTA-fed groups. It was found persistent even after 21?days of withdrawal of toxin-contaminated feed in all tissues except RBCs hemolysate. Present study described the OTA-induced oxidative stress as indicated by the low levels of SOD, GPx and TAS in different biological samples of broiler chicks.     

Development of diltiazem deacetylase and demethylase activities during ontogeny in rabbit

1. Diltiazem (DTZ) undergoes extensive metabolism in hepatic and extrahepatic tissues. Deacetyldiltiazem (M1) and N-desmethyldiltiazem (MA) are two of the main basic metabolites of DTZ that retain pharmacological activity. The development of DTZ deacetylase and demethylase activities through ontogeny has not been addressed. In order to address this issue, in vitro studies have been carried out using the blood and several tissues of rabbit as enzyme sources. In addition, in vivo studies using a pharmacokinetic approach were carried out to support the in vitro findings. 2. DTZ was incubated with homogenates of selected tissues and in whole blood and DTZ, and its metabolites were assayed by HPLC. In addition, a pharmacokinetic study after intraperitoneal administration of DTZ in the 1-, 8-, 16-, 30-day-old and adult rabbit were also carried out. 3. DTZ deacetylase activity was detected whatever the age and tissue examined (including blood). Except in gut homogenates, this activity was shown to be higher at earlier postnatal ages. DTZ demethylase activity was only detected in the liver and gut homogenates and in whole blood. This activity increases from the 1- to 30-day-old rabbit (except for blood), after which it decreases slightly to reach the adult level. 4. In vivo experiments showed a close pharmacokinetic profile throughout ontogeny (except for the 30-day-old rabbit) after DTZ intraperitoneal administration. 5. Extrahepatic metabolism may play a more significant role in the overall metabolism and pharmacokinetics of DTZ at earlier stages of development. 6. Finally, in vivo studies suggest that age does not seem to modify DTZ disposition and, for this reason, dosage may not have to be taken into account as a function of age.     

皮肤洗消剂PF2009对化学毒剂的消毒作用

目的通过检测皮肤洗消剂PF2009对化学毒剂的体外消毒效率,对皮肤洗消剂PF2009的消毒效果进行评价。方法将皮肤洗消剂PF2009按比例分别同梭曼（GD）、维埃克斯（vx）、芥子气（HD）混合,采用色谱分析法或T-135法于不同作用时间检测化学毒剂的剩余量。将皮肤洗消剂PF2009及其基质分别按相同比例与GD、VX或HD相互作用．1h后利用反应混合物进行在体动物实验．染毒后6d内观察动物存活情况,进行乙酰胆碱酯酶（ACHE）活性检测．或通过观察皮肤损伤面积及组织病理学变化等指标评价皮肤洗消剂PF2009的消毒效果。结果洗消剂对VX和GD具有快速、高效的消毒效果,在洗消剂与两毒剂分别按照体积比50：1进行消毒时,相互作用10min后,其消毒效率均大于99％：洗消剂对HD也具有较好的消毒效果,混匀后静置10min,消毒率达到80％以上,静置60min,其消毒率达到94％。毒剂与洗消液有效成分的摩尔比为1：10时。混匀60rain后GD消毒产物按照GD剂量4．54、9．0mg／kg（以初始加入GD量计）腹腔注射（ip）家兔。VX消毒产物3．34mg／ks（以初始加入VX量计）ip家兔,6d之内家兔全部存活,血液AChE活性均为正常对照的90％以上．而对应的基质对照组动物全部死亡。HD与PF2009消毒产物1mg／cm。皮肤染毒组同HD基质消毒对照组相比皮肤损伤明显减轻。结论皮肤洗消剂PF2009在体外对毒剂具有很好的消毒效果。     

Effect of simvastatin treatment on rat livers subjected to ischemia/reperfusion

We evaluated the effect of simvastatin (SV) on the oxido-redox state in rat livers submitted to ischemia-reperfusion (I/R). Rats received SV (groups: S, S-IR) or saline solution (groups: C, C-IR) intragastrically (25 mg/kg) for 21 days. Before homogenization, rat livers (C-IR, S-IR) underwent ischemia (40 min) and reperfusion (60 min). Activities of such antioxidative enzymes as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) as well as lipid peroxides (LPO) level as indicator of oxidative stress were then estimated in the homogenates. All these parameters were measured spectrophotometrically. Additionally, alanine and asparagine aminotransferase (ALT, AST) levels were estimated in the blood before and after I/R. In groups C and S all examined parameters were similar regardless of SV-treatment. I/R produced significant increases in GPx and CAT activities only in the C-IR group. Conversely, GPx activity was significantly decreased and ALT and AST increased significantly in the S-IR group. SV did not evoke any noticeable protective changes in rat livers after 3 weeks of treatment. After I/R, some of the observed properties could suggest that SV may have even made liver function and the oxidative state worse.     

Binding of non-steroid anti-inflammatory drugs and warfarin to liver tissue of rabbits in vitro

Liver slices (10mm 0.1mm thickness) were incubated at 37 degrees C in drug solutions up to 360 min. The drugs were dissolved in Ringer solution of pH 7.0. After 60, 180, 240 and 360 min each drug concentration was determined in the incubation fluid. For all drugs tested equilibrium was obtained after 240 min. The amount of drug taken up by the slices was calculated from the difference to initial concentration. In parallel, samples of the slices were homogenized together with their incubation fluids after the same incubation intervals. The free concentration was determined by ultrafiltration. For warfarin and several non-steroid anti-inflammatory drugs (NSAID), i.e. acetylsalicylic acid, ibuprofen, ketoprofen and oxyphenbutazone, there was no difference between the free drug concentrations in the homogenized and in non-homogenized samples. This suggests that the binding of these drugs to liver tissue was not altered by homogenization. Further was studied whether NSAIDS interfere with binding of warfarin to liver tissue. Acetylsalicylic acid, flurbiprofen, ibuprofen, ketoprofen, oxyphenbutazone and proquazon markedly increased the free concentration of warfarin both in liver slices and homogenates (p less than 0.01). The extent of displacement did not differ between slices and homogenates.     

Metabolism of sulfadiazine in neonatal and young pigs. Comparative in vivo and in vitro studies

Metabolism of sulfadiazine (SDZ) was studied in vivo and in vitro during postnatal development of piglets in order to examine whether in vitro metabolism approaches the in vivo situation. Experiments were performed in 1-day-, 8-day- and 60-day-old piglets. In vivo: 14C-SDZ was injected intravenously and urine and tissue samples collected after 3 hr. Urinary excretion data as well as data from liver and kidney tissue indicated a relatively high capacity for acetylation at birth, while the capacity for oxidation is low during the first week of life. At 60 days of age the acetylation and oxidation of SDZ is equal each accounting for about 20% of the amount excreted in urine. In vitro: Incubation of subcellular fractions of liver and kidney showed that acetylation of SDZ in liver reached maximum within 1 week. Oxidative activity was absent at 1 day, present at a low level at day 8, and at a high level at day 60. Neither acetylation nor oxidation of SDZ took place in kidney. The results show a close correlation between in vivo and in vitro results with respect to the developmental pattern seen in piglets during the postnatal period of life.     

Ontogenic aspects of liver and kidney catechol-O-methyltransferase sensitivity to tolcapone.

1. The present work describes the catechol-O-methyltransferase (COMT) activities in the liver and kidney of developing and adult rats (aged 3, 6, 9, 18, 30 and 60 days; n = 5 per group) and evaluates the enzyme sensitivity to inhibition by tolcapone, a reversible COMT inhibitor. 2. COMT activity, evaluated by the ability to methylate adrenaline to metanephrine, was determined in liver and kidney homogenates prepared in 0.5 mM phosphate buffer (pH = 7.8) containing pargyline (0.1 mM), MgCl2 (0.1 mM), EGTA (1 mM) and S-adenosyl-L-methionine (0.1 mM). Vmax (in nmol mg-1 protein h-1) of liver COMT was found to decrease gradually with age, from 5.3 +/- 0.5 at the age of 3 days up to 2.9 +/- 0.2 at the age of 60 days; for the same age range, Km values (in microM; geometric means with 95% confidence limits) increased from 3.3 (1.0, 7.5) up to 13.1 (2.1, 24.1). At the age of 3 days, Vmax values for kidney COMT (2.6 +/- 0.1) were lower than those for the liver COMT. However, Vmax values for kidney COMT were found to increase up to 6.2 +/- 0.6 at the age of 18 days and then declined by 44% at the age of 30 and 60 days. In kidney, aging was also accompanied by an increase in Km values for COMT (from 2.7 [1.1, 4.3] up to 24.0 [11.7, 36.3]). 3. The sensitivity of liver and renal COMT activity to tolcapone was markedly dependent on the age, 3-days old rats being more sensitive to tolcapone than older animals. The IC50 values (in nM) for inhibition of liver COMT by tolcapone increased gradually with age, from 41 (26, 65) at the age of 3 days up to 720 (640, 800) at the age of 60 days. As was found in the liver, IC50 values (in nM) for inhibition of kidney COMT by tolcapone also increased with age, from 8 (6, 10) at the age of 3 days up to 177 (131, 240) at the age of 60 days. In all experimental groups, the IC50 values for inhibition of liver COMT by tolcapone was higher than those for kidney COMT. 4. In conclusion, these results suggest that aging is accompanied by a decrease in liver and kidney COMT affinity for the substrate (evidenced by the increase in Km values) and a decrease in sensitivity towards inhibition by tolcapone (evidenced by the increase in IC50 values). Furthermore, kidney COMT is shown to be more sensitive to inhibition by tolcapone than liver COMT, irrespective of the age of the animal.