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The present study investigated the effect of Lentinan on the biochemical events associated with the pyrimidine and nucleic acid syntheses in the liver, kidney, thymus and spleen of rats. Lentinan was used at a dose of 4 mg/kg/day (twice) and in a single dose of 20 mg/kg. The following changes were observed. (1) The utilization of (14C)orotic acid for the synthesis of uridine components of liver acid-soluble extract and RNA uracil was activated after the administration of both doses of the drug. The specific activity of cytidine components of the acid-soluble extract and RNA were, on the other hand, not affected. The same holds true for the kidney. The ratio of the specific activity of cytidine:uridine components of the acid soluble extract as well as RNA decreased after the administration of both doses of the drug. The specific activity of DNA cytosine and thymine are slightly suppressed in the liver after the administration of a high dose of Lentinan; no effect was observed in the kidney. (2) The uptake of (14C)cytidine by the liver was not affected; the specific activity of DNA cytosine and thymine were increased after the administration of a high dose of Lentinan. (3) The uptake of (14C)thymidine by the liver was not affected; the specific activity of liver DNA thymine was increased after the administration of both doses of the drug. In the thymus an increase of specific activity of DNA thymine has also been observed. (4) Repeated doses of the drug (4 mg/kg for 6 consecutive days) increased the weight of the spleen. The specific activity of DNA thymine of the liver and spleen were significantly increased.

A pharmacokinetic profile of 14C-AdDP with uniformly labelled alanine was investigated. It was shown that the distribution phase after an i.v. administration is very short with a half-life of 2.1 min. The half-life of elimination phase after the i.v. administration is about 2.85 hours, that is longer than those of MDP and its derivatives. The total body clearance (30 ml/min/kg) is caused predominantly by metabolism of the compound. All the radioactivity found in urine in a 48 hours interval after a s.c. administration represents only 3.1% of the administered dose. Only a smaller part of the excreted radioactivity is formed by unmetabolised AdDP. The concentration curve after a s.c. administration is characterized by a very fast absorption with a half-life shorter than 1 minute. The distribution and elimination phases are prolonged (20 min, 11 hours respectively) in comparison with an i.v. injection. The decreased absolute bioavailability after a s.c. administration (65%) is probably not biologically significant because of a slower release of the compound from the site of the s.c. administration. A relatively very high radioactivity was found in liver, kidney, thymus, spleen and brain very soon which suggest a very good penetration into tissues. It is an agreement with the high apparent distribution volume of peripheral compartment and higher lipophilicity of AdDP as compared to MDP.

Binding difference spectra of rat renal and hepatic cytochromes P-450 with cyclosporine A (CsA) were measured. In both cases reversed type I spectra were found with the absorbance maximum at 416 nm and minimum at 378 nm. Apparent spectral dissociation constant Kd and maximal absorbance difference delta Amax416-378 did not change substantially with the concentration of the CsA stock solution used. The results suggest that CsA might be biotransformed not only in the liver but also in the kidney.

The administration of the lipophilic 3,7-bis-(4-trifluoromethylphenyl)- 1,5,3,7-dioxadiazocane (TFMPD) to rats induced the following effects on the biosynthesis of DNA in the liver, kidney, thymus and spleen: (a) The utilization of [3H]thymidine for the synthesis of liver DNA thymine was decreased after the administration of a single dose of the drug. The depression of the specific activities of DNA pyrimidines of liver DNA in experimental groups was observed also after an injection of [14C]orotic acid. (b) A decreased incorporation of labeled thymidine had occurred also in the spleen during the prereplicative period. Thereafter the specific activity of DNA thymine was higher than in the control group. (c) The observed mitogenic response in the spleen showed a protracted effect; after the administration of a single dose of the drug the specific activity of DNA thymine as well as the thymidine kinase activity of spleen cytosol have been rising up to the ninth day. The same holds true for DNA thymine of the thymus; the activity of thymidine kinase was not affected. (d) Both the single and repeated doses of TFMPD had no marked effect on the levels of microsomal cytochromes P-450 and b5 in the liver and kidney.

The effect of cyclosporine A (CsA), the immunosuppressant used in transplantation and also in the treatment of some autoimmune diseases, on the microsomal mixed function oxidase (MFO) systems in rat kidney and liver was studied. Since CsA given intragastrically (50 mg/kg/day) for three consecutive days decreased body, liver and kidney weights, in rats, the results were compared not only with the control untreated animals but also with the group of fully starved rats. In the liver the cytochrome P-450 level and aniline-hydroxylase activity were slightly higher than in the control rats but not as high as in the fully starved animals. This suggests that in the liver the effect might be the result of the antagonism between the CsA action and partial starvation of the CsA-treated animals. On the other hand, in the kidney the cytochrome P-450 level was as high as in the fully starved animals and the aniline-hydroxylase activity was significantly increased as compared to both the control and fully starved animals. Thus, in the kidney the microsomal MFO system seems to be induced after short-term CsA treatment. The activities of aminopyrine-N-demethylase and the levels of cytochrome bs did not change significantly after CsA treatment in both organs.

Muramyl dipeptide (MDP) protection from acrolein, chloroform and carbon tetrachloride toxicity was tested using isolated rat hepatocytes prepared by collagenase perfusion method. Hepatotoxin lethal effects were assessed using trypan blue exclusion and ascertained by LD leakage test. Incubation of hepatocyte suspensions with acrolein (143 mumol/ml), CHCl3 (124 mumol/ml) and CCl4 (103.5 mumol/ml) for 15 min reduced viability to 62%, 13% and 27%, respectively. Pretreatment of hepatocytes in incubation media with MDP (20.6 nmol/ml) increased viability significantly to 83%, 27% and 46%, respectively (P less than 0.01 and P less than 0.05). MDP single treatment in vivo (8.26 mumol/kg) produced a three-fold decrease in the high serum aspartate and alanine transaminases induced by CCl4 (5.2 mmol/kg). MDP modulation of CCl4 hepatotoxicity was not accompanied by reduction of lipid peroxides either in liver homogenates, microsomes or hepatocytes in the present conditions. It is suggested that MDP in certain dosages may produce nonspecific stabilization of cytoplasmic membranes towards the studied cytotoxins.

Like other lipid-soluble xenobiotics, clofibrate (ethyl-2-(4-chlorophenoxy)-2-methylpropanoate) increased the level of microsomal cytochrome P-450 in liver and decreased the utilization of 14C-orotic acid for the synthesis of hepatic cytidine nucleotides. This phenomenon was associated with the increased (a) uptake of 14C-cytidine, (b) total content of cytidine components of the acid-soluble extract and (c) utilization of this nucleoside for the synthesis of RNA. No changes were observed in uridine components. Clofibrate also increased the level of cytochrome P-450 in kidney microsomes; the degree of induction was almost the same as in the liver. The variations of renal pyrimidine metabolism after administration of the drug were analogous to those observed in the liver.

The present study was carried out to investigate the effect of single and multiple doses of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) on CCl4-induced hepatotoxicity, and hence some of the mechanisms involved. MDP (8.26 mumol/kg i.v.) was administered to rats according to different protocols followed by a single dose of CCl4 (5.2 mmol/kg i.p.), and either the hepatocytes were subsequently isolated and tested for viability and lipid peroxides formation or the level of serum aminotransferases and lactate dehydrogenase (LD) was measured. The results clearly indicate that MDP pretreatment in a single dose reduced CCl4 hepatotoxicity as judged from viability tests as well as reduction of elevated lipid peroxides induced by CCl4 administration. The level of lactate dehydrogenase was also brought to normal value by single MDP administration. MDP also decreased significantly the CCl4-elevated Ca2+ content of isolated hepatocytes and postmicrosomal supernatant Ca2+. 14C-palmitic acid incorporation was increased significantly for neutral lipids and/or phospholipids in hepatocytes and certain subcellular fractions under MDP treatment in vivo. A different effect was seen after multiple MDP administration which further increased CCl4-induced elevation of aminotransferases. Even the repeated administration of MDP without CCl4 increased the level of the latter enzymes. It may be concluded that a single administration of MDP can protect liver cells from CCl4 injury by a mechanism affecting the plasma membrane.

The utilization of (2-14C)orotic acid for the synthesis of cytidine components of the acid-soluble extract and for the RNA cytosine is decreased in the liver of rats which fasted for 24 or 72 h. The depression of the specific activity of the cytidine components is greater in animals which received alpha-HCH during the 24-hour interval after removal of food than in the control group; by contrast, the specific activity of the cytidine components again increases in rats fasting for 72 h. Analogous changes also occurred in the specific activity of RNA cytosine. Both the (U-14C)cytidine uptake and its utilization for the synthesis of RNA cytosine are enhanced in fasting rats; the administration of alpha-HCH has a potentiating effect. The total content of cytidine components of the acidsoluble extract of 1 g of liver tissue is enhanced 24 h after the animals of the control and experimental group were deprived of food. There are no marked differences in the concentration of the uridine components. Fasting has an additive effect on the increase of cytochrome P-450 level in the alpha-HCH treated rats. Alpha-HCH = alpha-1,2,3,4,5,6-hexachlorocyclohexane.