Research communications in chemical pathology and pharmacology最新文献

Cyclohexanediaminetetraacetic acid (CDTA), an effective antagonist for the treatment of zinc, lead, and manganese poisoning was evaluated for maternal and developmental toxicity in pregnant Swiss mice. CDTA was given intraperitoneally on gestation days 6-15 at doses of 0, 270, 540, and 1080 mg/kg/day. On gestational day 18, the fetuses were examined for external, visceral, and skeletal malformations and variations. Treatment with CDTA at 1080 mg/kg/day resulted in a high level of maternal deaths, as well as less severe clinical signs (significant reduction in weight gain and food consumption). Increased resorptions, fetal deaths, and decreased number of live fetuses per litter were observed at 1080 mg/kg/day. Mean fetal body weights were also significantly decreased in this group. At 1080 mg/kg/day, CDTA caused external malformations, while the development of skeletal tissues was less affected. The no observable adverse effect level (NOAEL) for maternal and developmental toxicity of CDTA in mice was 540 mg/kg/day. Analyses of maternal and fetal tissues revealed only slight effects of CDTA on concentrations of calcium, magnesium, zinc, copper and iron. According to these results, the alterations in mineral metabolism should not be the major reason for CDTA-induced developmental toxicity.

The renal handling of two anticancer (a-Ca) pyrimidines 5-fluorodeoxyuridine (FUdR) and 5-fluorouracil (5-FU) was investigated in clearance experiments in CF-1 mice using specific inhibitors of classical renal transport systems. The 5-FU was derived from the metabolism of FUdR. Based on the FUdR:inulin clearance ratio and 5-FU:inulin clearance ratio, it was determined that FUdR was secreted into renal tubules while 5-FU underwent reabsorption. The secretion of FUdR was inhibited by cimetidine and dipyridamole but not by probenecid or phloridzin. While the clearance ratio of 5-FU:inulin was significantly reduced by phloridzin, it (i.e., the ratio) was not affected by cimetidine, dipyridamole, or probenecid. The impact of two calcium channel blockers, diltiazem (DZM) and verapamil (VER), on the renal handling of FUdR and 5-FU was also examined. VER increased the secretion of FUdR without affecting the reabsorption of 5-FU while DZM slightly decreased the secretion of FUdR and prevented the reabsorption of 5-FU. These data suggest that the organic cation carrier and a dipyridamole-sensitive nucleoside transporter are involved in the renal excretion of FUdR; that the renal transport of both FUdR and 5-FU is associated with the calcium channel; and that 5-FU utilizes, at least in part, the glucose transporter for its reabsorption.

A number of tetrazole analogs of carboxylic substrates and inhibitors have been tested. Lactic and pyruvic tetrazoles were found to be competitive inhibitors of rabbit muscle L-lactate dehydrogenase in both the pyruvate reduction and the lactate oxidation reactions (Ki's of 0.04 M and 0.08 M D,L-lactic tetrazole and 0.02 M and 0.035 M pyruvic tetrazole, respectively). Lactic tetrazole is a non-competitive inhibitor of yeast L-lactate dehydrogenase (Ki = 0.10 M D,L-lactic tetrazole) while pyruvic tetrazole is predominantly competitive (Ki = 0.15 M). Alanine tetrazole is a poorer substrate than alanine for D-amino acid oxidase. It also acts as weak inhibitor. Benzoic tetrazole is a substrate-competitive inhibitor of D-amino acid oxidase (Ki = 0.7 mM) and is also a stronger ethanol-competitive inhibitor than benzoic acid (Ki = 0.03 M) of liver alcohol dehydrogenase. In all the substrates and inhibitors tested, substitution of a tetrazole ring for a carboxylic group has resulted in decreased binding, presumably due to a dilution of the negative charge density and the larger size of the tetrazoyl anion.

Experiments were performed on normotensive rats exposed to vitamin D deficient and control diets from the 22nd to the 180th day of age. In 60-120- and 180-day-old rats. The following parameters were evaluated: a) The vasomotor responses elicited by receptor agonists in the absence and in the presence of the respective antagonists [L-norepinephrine (NE) before and 5 min after prazosin; L-isoprenaline (I) before and 5 min after DL-propranolol; L-dopamine (DA) before and 5 min after L-sulpiride or SCH 23390 or chlorpromazine; acetylcholine (Ach) before and 5 min after atropine; histamine (H) before and after chlorpheniramine; 5-hydroxytryptamine (5-HT) before and 5 min after methysergide or ketanserin]; by carotid-sinus baroreceptor stimulation (CO) before and 5 min after hexamethonium, and by electrical stimulation of the vagus peripheral head (V) before and after atropine; b) Reflex tachycardia elicited by bilateral carotid occlusion (CO) (for 40 sec) and by sodium nitroprusside; c) Catecholamine (norepinephrine, epinephrine) and arginine-vasopressin plasma levels; d) Cholesterol, triglyceride and electrolyte (Na+, K+, Cl-, Ca2+) serum levels. Our results showed that vitamin D deficient diets induced a decrease in pressor responses to NE and CO, and an increase in hypotensive responses to I, DA, Ach, H, 5-HT and V. Changes of arterial blood pressure, heart rate, catecholamine and arginine-vasopressin plasma levels were not observed. Cholesterol, triglyceride and electrolyte (Na+, K+, Cl-) serum levels were not modified, while Ca2+ serum levels decreased. In conclusion, our data suggest that vitamin D depletion can induce changes of pressor and depressor vasomotor responses and suppose a direct role for vitamin D in regulating vasomotor reactivity.

N-Acetylation, which is catalyzed by the enzymes N-acetyltransferase (NAT), is an important biotransformation pathway for the elimination of a wide variety of xenobiotics. Based on reports by several investigators that hydrocortisone (HYD) pretreatment increases N-acetylation in the rabbit, we examined the potential of glucocorticoids to induce NAT in the rat. Rats received pretreatment with relatively equipotent doses of HYD, prednisolone (PRED) or dexamethasone (DEX) for 5 or 10 days. Livers were removed 24 hr after the last dose and NAT activity was determined by measuring the formation of N-acetylprocainamide in cytosolic incubations in the presence of 0.42 mM acetyl CoA. All three glucocorticoids were found to cause a modest induction of NAT activity towards procainamide after dosing for 10 days. When normalized to cytosolic protein content, the potency of induction was PRED > DEX > HYD (30, 29 and 18% increase, respectively), while normalization to liver weight demonstrated equipotent NAT induction by the three agents (40%). These data indicate that glucocorticoids are capable of producing a modest induction of NAT activity in the rat.

In a search for clinically useful indices of liver microsomal function, the correlation between various ratios of serum thyroid hormones, triiodothyronine (T3) and reverse T3 (rT3), and liver microsomal P-450 was investigated in CCl4-treated and untreated rats. Serum and liver samples were obtained before (untreated group, n = 15) and 4 hr after CCl4 administrations (0.2 ml/kg, s.c.). The CCl4-treated group (n = 11) included five randomly chosen untreated rats. In both groups, the ratios of T3/rT3, rT3/T3, and T3/T3+rT3 correlated significantly with liver cytochrome P-450 levels. From these results, it is suggested that the ratios of T3/T3+rT3, T3/rT3, and rT3/T3 can be used as the indices of liver microsomal P-450 levels and that thyroid hormone metabolism is related to liver cytochrome P-450, as was evidenced in untreated animals.

To examine whether the dosage of a platelet-suppressive agent at which an antithrombotic effect is adequate and bleeding tendency is not increased can be found, the antithrombotic effects, antiplatelet effects and bleeding times of ticlopidine and aspirin were investigated in the rat experimental thrombus formation model. Thrombus formation was determined by measuring the change in wet weight of a silk thread placed in a carotid arteriovenous shunt. Ticlopidine inhibited thrombus formation and platelet aggregation at rather low doses (50-100 mg/kg) without prolonging bleeding time. However, aspirin did not inhibit thrombus formation at even the highest examined dose (200 mg/kg), while bleeding time was prolonged at even the lowest dose (50 mg/kg). These results suggest that a dosage of antithrombotic agent that does not increase bleeding tendency can be easily established using ticlopidine, although it is relatively difficult using aspirin.

To investigate the alteration of the renal atrial natriuretic peptide (ANP) and arginine vasopressin (AVP) receptors in the controlled hypertensive state of spontaneously hypertensive rat (SHR) treated with antihypertensive diuretics, 12 weeks old SHRs were administered an antihypertensive diuretic, furosemide, trichloromethiazide, or indapamide, daily for 10 days and investigated by radiolabeled receptor assay (RRA) of ANP and AVP. The urine volume was significantly increased in all groups treated with antihypertensive diuretics as compared with the untreated control group on day 3. Systolic blood pressure was significantly decreased in groups treated with both trichloromethiazide and indapamide. The number of renal ANP receptors decreased; affinity was increased only in the SHR administered indapamide. The affinity of the renal AVP receptor was also decreased in that group. Alteration of ANP and AVP receptors was observed only in the group treated with indapamide. This indicates that the ANP and AVP receptor in the kidney of SHR was changed not only by diuresis or reduction of blood pressure, but by the pharmacological action of indapamide.

To clarify the relationship between cytokines and arachidonic acid metabolites, we measured tumor necrosis factor (TNF-alpha), interleukin 8 (IL-8), and leukotriene B4 (LTB4). The subjects consisted of 30 patients with sepsis. The results were compared between patients who died (Group A) and those who survived (Group B). All TNF-alpha, IL-8, and LTB4 levels were significantly higher in Group A than in Group B, reflecting the severity of the disease. The LTB4 levels were significantly correlated with the TNF-alpha level and the IL-8 level. These results suggest that inflammatory cytokines, excessively produced due to inflammatory reactions, stimulate as a mediator the release of arachidonic acid, increasing LTB4 production.

In human fibroblast cultures TPA increased IL-6 and IL-8 production. This was reduced by vitamin D3 metabolites and analogs. The two analogs employed: 1,25 (OH)2-22 (E)-dehydro-24-monohomo vitamin D3 (Compound A) and 1,25 (OH)2 -22 (E)-dehydro-24 dihomo-vitamin D3 (Compound B) may be useful in the therapy of pathologic proliferative disorders including psoriasis, particularly since they are less toxic and have less effect on calcium metabolism than vitamin D3.