Cadmium ions influence the chemiluminescence activity of murine splenocytes both in vitro and in vivo.

The luminol-enhanced chemiluminescence (CL) activity of splenocytes of mice of the strain (CBA x C57B1)F1 was monitored after treatment with Cd2+ (cadmium chloride) in both in vitro and in vivo experiments. Cd2+ (at concentrations of 1 microM-1 mM) increased the CL reaction of the splenocytes (2 x 10(6) cells/ml) in vitro in a dose-dependent manner, both instantaneously and after incubation for 1 h. In in vivo experiments, Cd2+ was administered in two ways. Following a 14-day administration of cadmium to mice in drinking water (300 mg Cd2+/l), the CL reaction of the splenocytes was significantly reduced. On the other hand, after i.p. administration of CdCl2 dissolved in PBS (2 mg/kg body mass, repeated seven times during 14 days), the metabolic activity of the phagocytes was increased. From the results it follows that cadmium affects the immune system. However, its toxicity is dependent on the route of administration.

Postirradiation administration of adenosine monophosphate combined with dipyridamole reduces early cellular damage in mice.

The administration of dipyridamole and adenosine 5'-monophosphate (AMP) to mice 5 to 25 min after 1 Gy of total-body gamma irradiation was found to decrease cellular damage, as indicated by the thymidine level in plasma and the amount of saline soluble polynucleotides in the thymus. The drug combination used did not influence similar cytotoxic effects of hydrocortisone. Furthermore, it was shown that the addition of dipyridamole and AMP to in vitro irradiated suspensions of thymocytes enhanced the rejoining processes of DNA strand breaks. Receptor-mediated action of extracellular adenosine may be responsible for the therapeutic effects observed.

Protection of early cellular damage in 1 Gy-irradiated mice by the elevation of extracellular adenosine.

In whole-body 1Gy-irradiated mice a modification of early cellular damage by means of preirradiation dipyridamole and adenosine monophosphate (AMP) treatment was investigated. Both drugs were given either alone or in combination, AMP being administered i.p. at doses of 5, 10 and 15 mg, dipyridamole s.c. at the dose of 2 mg, 20 min before AMP. The thymidine level in plasma and the amount of free polynucleotides in the thymus and spleen, both estimated at the interval of 4 h after irradiation, were used as indices of early cellular damage in vivo. The elevated level of thymidine observed in the plasma of irradiated controls decreased significantly after the administration of AMP (5 mg) alone to 71%, after the combination of dipyridamole and AMP a still deeper significant fall to 60% was observed. Such a protective effect was observed when injecting AMP 15 min before irradiation. Using the interval of 65 min between AMP administration and irradiation, no protection was detected. The higher doses of AMP (10, 15 mg) enhanced the protective effect manifested in plasma thymidine level only moderately. The amount of free polynucleotides, elevated in the thymus and spleen of irradiated mice, was significantly decreased in the thymus of mice pretreated with the combination of dipyridamole and AMP. The results suggest that the treatment used decreases the radiation damage of the sensitive thymocyte population. It is proposed that the joint use of AMP, an adenosine prodrug, and dipyridamole, a drug inhibiting adenosine uptake by cells, leads to an elevation in extracellular adenosine which activates cell surface adenosine receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of cyclophosphamide and gamma irradiation on adenosine deaminase and purine nucleoside phosphorylase in mice.

Changes in ADA and PNP activities in the spleens and thymuses of mice were studied after a single administration of cyclophosphamide (CY, 200 mg/kg) and after whole-body gamma irradiation (5.5 Gy), applied alone or three days after CY application. In the first days after the treatment the enzyme activities were significantly depressed (p less than 0.01) with the exception of ADA in the spleen, where a high elevation (220-380%) in relation to controls was observed. During the regeneration period a pronounced rise of PNP activity in the spleen occurred mainly after a combined application of CY and irradiation (270%). In the thymus the regeneration was manifested by a mild increase of both ADA and PNP activities towards control values. The findings suggest that the expressive changes of ADA and PNP activities, participating in the purine salvage pathway, may, after a cytotoxic treatment, influence the nucleotide pool and DNA synthesis in lymphoid organs.

Production of anti-SRBC antibodies after DDC administration in whole-body irradiated mice.

Production of antibody-forming cells (PFC) was studied in mice subjected to a single whole-body irradiation dose of 3.8 Gy after sodium diethyldithiocarbamate (DDC, 800 mg/kg) injected 30 min before irradiation. Animals were immunized (1% SRBC) 4 h, 5 and 10 days after irradiation, and the number of PFC was determined by a modified Jerne plaque technique on days 4, 7 and 10 after immunization. After the irradiation alone, the PFC levels were markedly reduced at all time intervals in comparison with unirradiated controls. Upon immunization of animals on day 10 after irradiation the peak PFC levels were observed on day 7 after immunization in the only irradiated group and in the group irradiated after DDC administration (in controls on day 4 after immunization). Administration of DDC entirely eliminated the unfavourable effect of radiation if immunization was performed 4 h after irradiation, in terms of the number and the peak level of PFC. Upon immunization of animals on day 5 and day 10 after irradiation the PFC levels were not markedly influenced by DDC injection.

Purine metabolizing enzyme activities in radiosensitive tissues of mice after sublethal whole-body irradiation.

The activities of adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) were determined between days 1-14 in the spleen, thymus and femoral bone marrow of mice subjected to whole-body gama irradiation with a dose of 5.5 Gy. In control animals, the highest activity of ADA (as related to 10(6) cells) was recorded in the thymus (58.9 pmol.s-1), the lowest one in the femur (34.8 pmol.s-1), the PNP activity was the lowest in the thymus (14.5 pmol.s-1) and the highest in the femur (96.0 pmol.s-1). In the spleen, an elevation of ADA activity (up to 379%) was observed during the first postirradiation days; PNP activity was reduced (to 58%) on postirradiation day 3, followed by the return and even elevation on day 14 (265%). In the thymus, a parallel reduction of the activities of both enzymes appeared during the first postirradiation days, with a subsequent increase during the regeneration phase. In the femoral bone marrow, ADA and PNP activities were increased on postirradiation day 1 (275% and 201%, respectively). Reference is made to the possible relationship between the observed characteristic changes in activities and the degree of damage and/or renewal of cell population in the hemopoietic tissues after irradiation.

Determination of adenosine deaminase and purine nucleoside phosphorylase activities using high-performance liquid chromatographic and radiochromatographic methods.

Two methods for the determination of adenosine deaminase and purine nucleoside phosphorylase activities were compared. The high-performance liquid chromatographic (HPLC) technique used separation on a reversed-phase silica column and exhibited adequate sensitivity and a markedly higher rate of analysis compared with that of the paper radiochromatographic method. Correlation analysis of the results obtained by the two methods on a set of lymphoid cells from 25 patients with lympho-proliferative disorders confirmed the utility of the HPLC technique in clinical investigations.

The fall in the incorporation of labelled iron into the bone marrow during enhanced erythropoiesis: this paradox explained by changes in ferrokinetics and cytokinetics using the model of mice affected by thyroid hormones.

Using the model of mice affected by thyroid hormones, a ferrokinetic analysis was made of the repeatedly observed paradoxical fall in the incorporation of labelled iron into the bone marrow under conditions of the overall stimulation of erythrocyte formation.

The effect of hypoxia on the activity of purine nucleoside phosphorylase in rats.

The activity of purine nucleoside phosphorylase (PNP) in rat erythrocytes fractionated by centrifugation in microhematocrit capillaries was studied. After seven-day hypoxia (54 kPa) the PNP activity was increased by 67 +/- 4% (S.E.M.) in the lightest fraction of erythrocytes; on the fifth day after hypoxia PNP activity did not differ from control values.

Stimulatory effect of intermittent feeding on hemopoietic recovery in sublethally gamma-irradiated mice.

The effect of three-week adaptation to intermittent feeding on the recovery of the hemopoietic functions of mice after sublethal gamma irradiation was investigated. Measurement of oxygen consumption, carbon dioxide output and the respiratory quotient demonstrated an increased metabolic rate in the intermittently fed animals and an accentuation of lipogenic processes. This metabolic state persisted even after irradiation. An improvement in the recovery of hemopoietic functions after irradiation was demonstrated in adapted animals, which was reflected by the increased proliferative activity of the hemopoietic cell populations (more intensive incorporation of 125I-UdR into the DNA of cells of the spleen, thymus and femoral bone marrow), by more rapid renewal of spleen weight, more rapid recovery of the femoral bone marrow cellularity and increased levels of granulocytes in peripheral blood.

Protective efficacy of combined administration of lipopolysaccharide of E. coli and chemical radioprotectors under conditions of prolonged irradiation.

We investigated the protective effectiveness of the lipopolysaccharide of E. coli (LPS) in a combination with a mixture of chemical radioprotectors in female mice of the strain H at various radiation dose rates. LPS in a dose of 0.08 mg per kg of body mass was administered 1, 3, or 24 hours prior to irradiation, the radioprotective mixture (cystamine 90 mg X kg-1 + 5-methoxytryptamine 15 mg X kg-1) was administered 10 minutes before irradiation. Dose rates of 612 mGy X min-1 (irradiation time 10 to 15 minutes), 38 mGy X min-1 (3 to 4 hours), and 8.2 mGy X min-1 (27 to 29 hours) were used. The results showed that isolated administrations of LPS or of the radioprotective mixture increased the resistance of the mice against prolonged irradiation; the combined administration even enhanced the efficacy of the radioprotective action. However, this efficacy depended on the magnitude of the dose rate. At dose rates higher than 38 mGy X min-1 the effectiveness of the chemical protection prevailed, whereas at lower dose rates the biological and especially the combined protection became effective. We demonstrated a slight pyrogenic effect of LPS by measuring oxygen consumption and changes in some parameters of the hematopoiesis.

Resistance to prolonged irradiation in mice influenced by thyroid hormones and chemical radiation protectors.

After the end of 10 and 21 days' treatment of mice with dried thyroid gland (0.6 g/100 g diet) the effect of some radiation protectors against prolonged irradiation (38 mGy/min) increased. The combination of propranolol, phenobarbital and cystamine was more effective than a mixture of cystamine and 5-methoxytryptamine both in mice fed on a normal and a thyroid gland diet. A reduced oxygen consumption after the application of protectors reflected the degree of protection. The number of thrombocytes in peripheral blood increased after the end of thyroid treatment, which indicated a possible shift in the differentiation of stem cells in favour of megakaryocytes.

Characterization of the protective effect of radioprotective substances by means of long-term changes in oxygen consumption.

A comparison of long-term hypothermic effects of radioprotective substances and their protective effectiveness was carried out in mice after acute and prolonged irradiation. As radioprotective substances were used AET, cystamine, serotonine, 5-methoxytryptamine, cysteamine-S-phosphate, sodium fluoroacetate and some double combinations of these substances. The irradiation was carried out with dose rates 38.3 and 612.5 mGy/min, the hypothermic reaction was evaluated according to total oxygen consumption, measured during 5 hours after the drug administration. The results demonstrated the existence of a correlation between the suppression of metabolic processes and both short-term and long-term protective effectiveness of radioprotective substances. The protective effectiveness of a drug is the higher, the greater decrease of oxygen consumption is induced by this substance in the investigated time interval. An analogous dependence was also demonstrated between the duration of hypothermic and radioprotective effects. The found correlation is valid for both acute and prolonged irradiation (correlation coefficient 0.79-0.87; p < 0.01).

Influence of the thyroid hormones on erythropoiesis and radiation resistance in C 57 black mice.

Oral administration of dried thyroid gland to C57Bl adult male mice in a dose of 0.6 g per 100 g diet during 10 days increased the metabolic rate and stimulated the erythropoiesis. Three to six days after thyroid pretreatment the radiation resistance of the mice increased, as revealed by their 30-day survival and a higher recovery of peripheral blood cell counts. The period of increased resistance to radiation was correlated with the receding of hypermetabolic effects and with the increase of repopulating abilities of the bone marrow cells.

Dynamic characteristics of a metabolic reaction of mice with different responses to irradiation.

The course of the reaction of mice placed in a metabolic chamber and afterwards irradiated with an exposure dose of 610 R was studied by assessing total oxygen consumption and the size of its fluctuation. Fluctuation was greater in non-survivors than in survivors in the initial phase of the metabolic reaction only (P is less than 0.05), while the mean oxygen consumption values for the two groups were the same, In the distribution of the individual values there were more non-survivors in the frequency class with a high fluctuation level and, conversely, more survivors in the low level class (P is less than 0.01). Fluctuation during the studied reaction was more variable in survivors, despite its lower level, than in non-survivors. The reciprocal relationship between the size and fluctuation of oxygen consumption, determined for the whole series of experimental mice at given stages of the metabolic reaction, is linear. Attention is drawn to the association between changes measured in the metabolic rate and motor activity and to the possibility that it is determined by the individual's type of nervous activity.

The effect of dried thyroid gland pretreatment upon survival, formation of endogenous spleen colonies and differentiation of haemopoietic cell populations in x-irradiated mice.

Experiments on non-inbred H-strain male mice confirmed that their radioresistance could be increased by a stimulatory action of the thyroid hormones applied for three weeks preceding the radiation exposure. It was found that the 30-day survival after 750R rose between the 1st and the 5th day after the end of the pretreatment. The highest degree of radioresistance was observed, when the radiation exposure fell into the phase of gradual receding of increased metabolic rate. The relevant experimental groups showed a higher frequency of endogenous spleen colonies and an increased granulocytic differentiation of haemopoietic stem cells. Higher colony-forming activity was also found in animals irradiated immediately after the termination of pretreatment with thyroid, but without an increase in survival. The lack of radioprotective effect under those circumstances could be explained by the persisting hypermetabolic effect of the thyroid, and by the fact that an increased proportion of haemopoietic stem cells underwent differentiation into the erythroid line.