Radiation protection of murine intestine by WR-2721, 16,16-dimethyl prostaglandin E2, and the combination of both agents

The survival of murine intestinal clonogenic cells (ICC) and the survival of mice after whole-body exposure to 137Cs irradiation were used to measure radiation protection by ethiophos (WR-2721), 16,16-dimethyl prostaglandin E2, and the combination of the two. Doses from 2 to 12.5 mg/mouse of WR-2721 increased cell survival linearly from 3.2 +/- 0.3 in controls given 15.0 Gy to 93.1 +/- 5.2 per jejunal circumference. In contrast, 16,16-dm PGE2 increased ICC survival at 15.0 Gy rapidly from 1 to 10 micrograms/mouse, followed by a plateau up to 100 micrograms/mouse. Animal survival at 6 days (LD50/6) increased from 16.3 +/- 0.4 Gy (95% confidence limits) in controls to 20.3 +/- 0.6 Gy in the PG-treated animals. WR-2721 increased the LD50/6 to 26.1 +/- 1.4 Gy. The dose modification factors were 1.25 and 1.60, respectively. The combination of agents increased ICC survival above that seen with each agent alone up to 8 mg WR-2721, above which no additional protection was seen. Animals given 10 micrograms PG plus 10 mg WR-2721 survived longer than with either agent given alone. The LD50/6 was 36.3 +/- 1.8 Gy for a dose modification factor (DMF) of 2.23. In addition, the slope of the probit curve was reduced from those of each agent alone. PG-induced changes in villus epithelial cell morphology and survival may account, in part, for these observations. The results suggest that either the mechanisms for these two types of radiation protectors are different or they act on separate subcellular targets which are critical to survival from radiation injury.     

The effect of X irradiation on cardiac beta-adrenergic receptors in the rabbit

Cardiac beta receptors in rabbits were studied at different times following lethal (5 Gy) or supralethal (10 Gy) whole-body X irradiation. Using the radioactive ligand [125I]iodocyanopindolol, it was found that the maximal binding capacity, as determined from the Scatchard plot, decreased from 298.2 +/- 13.2 fmole/mg protein in controls to 142.4 +/- 5.5 fmole/mg 3 days after 10 Gy whole-body X irradiation, whereas the dissociation constant was only little affected. Three days after an exposure to 5 Gy, maximal binding capacity was reduced slightly and tended toward control values at Day 7. Local irradiation of the cardiac region with 10 Gy reduced cardiac beta receptors to 218 +/- 7 fmole/mg (73% of control) after 3 days. The latter observation suggests that about half the effect of radiation on cardiac beta receptors originates from a direct action of radiation on the heart tissue, the rest being due to abscopal systemic reactions.     

Nuclear scintigraphic assessment of radiation-induced intestinal dysfunction

Radiation-induced damage to the intestine can be measured by abnormalities in the absorption of various nutrients. Changes in intestinal absorption occur after irradiation because of loss of the intestinal absorptive surface and a consequent decrease in active transport. In our study, the jejunal absorption of (99m)Tc-pertechnetate, an actively transported gamma-ray emitter, was assessed in C3H/Kam mice given total-body irradiation with doses of 4, 6, 8 and 12.5 Gy and correlated with morphological changes in the intestinal epithelium. The absorption of (99m)Tc-pertechnetate from the intestinal lumen into the circulation was studied with a dynamic gamma-ray-scintigraphy assay combined with a multichannel analyzer to record the radiometry data automatically in a time-dependent regimen. The resulting radioactivity-time curves obtained for irradiated animals were compared to those for control animals. A dose-dependent decrease in absorptive function was observed 3.5 days after irradiation. The mean absorption rate was reduced to 78.8 +/- 9.3% of control levels in response to 4 Gy total-body irradiation (mean +/- SEM tracer absorption lifetime was 237 +/- 23 s compared to 187 +/- 12 s in nonirradiated controls) and to 28.3 +/- 3.7% in response to 12.5 Gy (660 +/- 76 s). The decrease in absorption of (99m)Tc-pertechnetate at 3.5 days after irradiation correlated strongly (P < 0.001) with TBI dose, with the number of cells per villus, and with the percentage of cells in the crypt compartment that were apoptotic or mitotic. A jejunal microcolony assay showed no loss of crypts and hence no measured dose-response effects after 4, 6 or 8 Gy TBI. These results show that dynamic enteroscintigraphy with sodium (99m)Tc-pertechnetate is a sensitive functional assay for rapid evaluation of radiation-induced intestinal damage in the clinically relevant dose range and has a cellular basis.     

Apoptosis in HeLa Hep2 cells is induced by low-dose,low-dose-rate radiation

Radioimmunotherapy with radiolabeled antibodies may cause inhibition of the growth of epithelial tumors, despite low total radiation doses and comparatively low radiosensitivity of epithelial tumor cells. The induction of apoptosis by low-dose radiation, such as delivered in radioimmunotherapy, was investigated in vitro in human HeLa Hep2 carcinoma cells. The cultured cells were exposed to defined radiation doses from a (60)Co radiation therapy source. The radiation source delivered 0.80 +/- 0.032 (mean +/- SD) Gy/min and the cells were given total doses of 1, 2, 5, 10 and 15 Gy. Using fluorescein-labeled Annexin V, followed by flow cytometry and DNA ladder analysis, apoptotic cells were detected and quantified. Radiation doses below 2 Gy did not cause any significant increase in apoptosis. Compared to control cells, apoptosis was pronounced after 5-10 Gy irradiation and was correlated to the radiation dose, with up to 42 +/- 3.5% of the cells examined displaying apoptosis. Clonogenic assays confirmed significantly decreased viability of the cells in the interval 2 to 10 Gy with low-dose-rate radiation, 60 +/- 2% compared to 2 +/- 2%. Lethal effects on the tumor cells were also evaluated by an assay of the cytotoxic effects of the release of (51)Cr. Significant cytotoxicity, with up to 64 +/- 6% dead cells, was observed at 5 Gy. Similar results were obtained when the dose rate was reduced to 0.072 +/- 0.003 Gy/min (mean +/- SD). In the case of the (137)Cs source, the dose rate could be reduced to 0.045 Gy/h, a level comparable to radioimmunotherapy, which induced significant apoptosis, and was most pronounced at 72-168 h postirradiation. It can be concluded that in vitro low-dose and low-dose-rate radiation induces apoptosis in epithelial HeLa Hep2 cells and thus may explain a mechanism by which pronounced inhibition of growth of HeLa Hep2 tumors at doses used in radioimmunotherapy has been obtained previously.     

Effect of a dopamine antagonist on ventilation during sustained hypoxia in mice

To test the hypothesis that dopamine accumulated in the carotid body limits hyperventilation during acclimatization to sustained hypoxia, we administered the dopamine antagonist droperidol to mice undergoing acclimatization to an inspired O2 fraction (FIo2) of 0.1. Twelve mice were exposed to hypoxia for 10 days and ventilation in 10% O2 and in 7% CO2 in air were measured daily by a plethysmographic method. Under both conditions ventilation increased during acclimatization to hypoxia: ventilation in 10% O2 increased from 39.4 +/- 3.8 (mean +/- SE) ml/min before exposure to sustained hypoxia to 72.2 +/- 4.2 ml/min after 3 days of continuous hypoxia, and ventilation in 7% CO2 in air at the same time increased from 113.2 +/- 5.4 ml/min to 140.0 +/- 5.6 ml/min. Twelve mice were exposed to FIo2 of 0.1 for 10 days and received droperidol (300 micrograms/kg intraperitoneally) before exposure to sustained hypoxia and on the 2nd, 4th, and 8th days of continuous hypoxia. Before exposure to sustained hypoxia, droperidol increased ventilation in 10% O2 from 40.1 +/- 2.5 ml/min to 72.5 +/- 5.2 ml/min, but after 2, 4, and 8 days of continuous hypoxia droperidol caused an acute fall in ventilation (ventilation in 10% O2 after droperidol on day 2: 49.1 +/- 3.1 ml/min, on day 4: 44.4 +/- 3.7 ml/min, and on day 8: 27.8 +/- 3.4 ml/min). Two days after the animals were returned to room air, ventilation in 10% O2 again increased in response to droperidol. We conclude that dopamine in the carotid body does not limit ventilatory responses to hypoxia during acclimatization to sustained hypoxia.     

Radiation-induced impairment of urinary bladder function in mice: fine structure of the acute response and consequences on late effects

The time course and dose response of radiation-induced impairment of urinary bladder function in the mouse were assessed after local irradiation with graded single doses. Bladder capacity was defined by transurethral cystometry; a reduction in bladder volume at an intravesical pressure of 10 mmHg by > or =50% of the individual pretreatment control value was considered a positive radiation reaction. Reversible effects of radiation on the urinary bladder were found during the first 30 days postirradiation, followed by a symptom-free latent period and irreversible late changes. Maximum-likelihood analysis revealed that the acute response is composed of two distinct waves from days 1-15 and days 16-30, with mean latent times of 7.1 days [95% confidence interval (5.4, 9.0)] and 23.3 days (21.9, 24.5), respectively, which describe the data significantly better than a single normal distribution (P = 0.0052). The ED50 values (+/- their standard deviation sigma), i.e. the doses at which 50% of the irradiated animals show the > or = 50% reduction in bladder capacity during each of the two intervals, were 21.7 +/- 4.1 and 19.3 +/- 3.9 Gy for the first and the second acute wave, respectively. The ED50 for the late functional effects was 18.7 +/- 2.4 Gy. Multivariate analysis demonstrated (1) that a response during the first acute wave correlated significantly with a reaction in the second acute wave (P = 0.0066), and (2) that a response during the second but not the first acute wave correlated significantly with the development of a late response (P = 0.0008). In conclusion, the present analysis suggests that the radiation response of the urinary bladder of the mouse displays a significant consequential component. However, further studies are required to demonstrate if the frequency of late sequelae can be decreased by an early intervention in the sequence of pathogenic processes.     

A comparison of the radiation response of the epidermis in two strains of pig

The response of the epidermis was compared in two strains of pig, the English Large White and the G?ttinger Miniature, after irradiation with 90Sr beta rays. The effects of two types of anesthesia were also tested in pigs of each strain, a volatile gas mixture of approximately 70% oxygen, approximately 30% nitrous oxide, and 2% halothane, and an intravenously administered narcotic azaperon/etimodat with the animals breathing air. Strain- and anesthetic-related changes were compared on the basis of dose-effect curves for the incidence of moist desquamation from which ED50 values (+/- SE) were determined, i.e., the dose required to produce this effect in 50% of the fields irradiated. For English Large White pigs anesthetized with the volatile gas mixture, an ED50 of 27.32 +/- 0.52 Gy was obtained for moist desquamation. Irradiation with the azaperon/etomidat anesthesia in this strain of pig produced a significantly higher ED50 of 33.36 +/- 0.76 Gy (P less than 0.001). This appeared to be related to the fact that the animals were breathing air, i.e., a lower oxygen concentration (approximately 21%), at the time of irradiation. For the G?ttinger Miniature pig the ED50 values for moist desquamation were 38.93 +/- 3.12 Gy and 43.36 +/- 1.34 Gy while using the gaseous anesthetic mixture and the azaperon/etomidat anesthesia with the animals breathing air, respectively. These ED50 values are 10-11 Gy higher than those obtained for the English Large White pig under identical conditions of anesthesia, which resulted in a strain difference ratio of approximately 1.35. Radiation under the volatile gas mixture anesthesia resulted in a uniform irradiation response over the skin of the flank in both strains of pig. Radiation under azaperon/etomidat anesthesia resulted in a nonuniform skin response over the flank. The ED50 for moist desquamation was significantly higher in dorsal sites on the flank compared with the ventral area of English Large White pigs; a similar trend was seen in G?ttinger Miniature pigs. This difference in the radiosensitivity over the flank skin while the animals are under azaperon/etomidat anesthesia at the time of irradiation was associated with the animals breathing air and is in agreement with findings published previously for animals under halothane anesthesia and breathing air.     

Langerhans cell number and morphology in mouse footpad epidermis after X irradiation

Effects of 250-kV X rays on epidermal Langerhans cells were studied in CBA/CaH mice. One group received 20 Gy to the feet, another 8 Gy to the whole body, and a third both the 8 Gy whole-body and a 12 Gy local dose to the feet. Mice from each group and controls were sacrificed at intervals from 1 to 64 days later. ATPase-positive cells in sheets of footpad epidermis were counted by light microscopy. The density of Langerhans cells in controls was 1515 +/- 36/mm2 (mean +/- SE; n = 34). By 3 days after irradiation they became rounded and less dendritic and numbers gradually reached a nadir by 10 days, at 18% of controls after 20 Gy and 57% of controls after 8 Gy. Some of the remainder exhibited bizarre morphology and ultrastructural abnormalities. After local irradiation of the feet Langerhans cell numbers recovered rapidly between 14 and 16 days, although their distribution was uneven until 30 days after irradiation. Repopulation was delayed after an 8 Gy whole-body dose by at least 3 weeks. These results demonstrate that high local doses of X rays substantially but transiently deplete the epidermal Langerhans cell population and support the hypothesis that functional hemopoietic tissue is required for extensive Langerhans cell replenishment.     

An evaluation of ventilation in dystrophic Syrian hamsters

Ventilatory responses of 10 control and 10 dystrophic male hamsters to air, hypercapnia, and hypoxia were evaluated at four ages (40, 70, 100, and 140 days). Tidal volume (VT), frequency (f), minute ventilation (VE) as well as inspiratory and expiratory time of awake animals were measured with a plethysmograph. There was a small increase of VT in both groups with age. Although there was no change of f in the control group with age, there was a progressive decrease in f (means +/- SE: 92 +/- 8, 97 +/- 9, 74.5 +/- 10, and 68 +/- 8 breaths/min) in the dystrophic group. Consequently VE on air decreased in the dystrophic group. Both groups showed similar responses to hypoxia (13 and 10% O2) and hypercapnia (3, 5, and 8% CO2) at 40 days. By 70 days the hypercapnic, but not hypoxic, response of the dystrophic animals was significantly decreased compared with that of the control group (at 8% CO2, VE = 47.4 +/- 4.1 vs. 75.7 +/- 7.6 ml/min, P less than 0.01). At both 100 and 140 days the response of the dystrophic group to CO2 was flat; i.e., the slope VE vs. fractional concentration of inspired CO2 was close to zero, and the hypoxic responses were greatly diminished. Because hamsters increase VE in response to CO2 primarily by increasing VT, the data suggest that dystrophic hamsters are unable to increase VT at a very early age, presumably due to muscle weakness. The normal response of hamsters to hypoxia, which is primarily to increase f, appears to be maintained for a longer time.     

Radiation tolerance of the rat spinal cord after single and split doses of photons and carbon ions

The sensitivity of the rat spinal cord to single and split doses of radiation and the resulting relative biological effectiveness (RBE) were determined for carbon-ion irradiations (12C) in the plateau and Bragg-peak regions. The cranial part of the cervical and thoracic spinal cords of 180 rats were irradiated with one or two fractions of 12C ions or photons, respectively. Dose-response curves for the end point symptomatic myelopathy were established, and the resulting values for the ED50 (dose for 50% complication probability) were used to determine the RBEs. A median latency for myelopathy of 167 days (range, 121-288 days) was found. The ED50 values were 17.1 +/- 0.8 Gy, 24.9 +/- 0.7 Gy (one and two fractions, 12C plateau) and 13.9 +/- 0.8, 15.8 +/- 0.7 Gy (one and two fractions, 12C Bragg peak), respectively. For photons we obtained ED50 values of 24.5 +/- 0.8 Gy for single doses and 34.2 +/- 0.7 Gy when two fractions were applied. The corresponding RBEs were 1.43 +/- 0.08, 1.37 +/- 0.12 (one and two fractions, 12C plateau) and 1.76 +/- 0.05, 2.16 +/- 0.11 (one and two fractions, 12C Bragg peak), respectively. Hematoxylin and eosin staining revealed necrosis of the white matter in the spinal cord in all symptomatic animals. In summary, from one- and two-fraction photon, 12C plateau and Bragg-peak irradiation of the rat spinal cord, we have established RBEs as well as the individual ED50's. From the latter there is a clear indication of repair processes for fractionated photons and 12C plateau ions which are significantly reduced by using Bragg-peak ions. Additional studies are being carried with 6 and 18 fractions to further refine and define the RBE and ED50 values and estimate the alpha/beta ratios.     

Radioprotective effect of polyethylene glycol

Polyethylene glycol of molecular weight 400 (PEG-400) had a radioprotective effect of about 20% against lethality when given ip 20 min prior to single or fractionated X-ray doses to the head and neck. Dose modification factors (DMF) based on LD50/15 values ranged from 1.14 to 1.24. A similar DMF of 1.12 based on LD50/30 values was obtained using single doses of whole-body X irradiation. Mice given head and neck irradiation had significantly reduced rectal temperatures (31.3 +/- 3.0 degrees C) 9 days post irradiation compared with unirradiated controls (35.4 +/- 0.6 degrees C). No such reduction was observed when PEG-400 was given with radiation (36.3 +/- 0.9 degrees C). PEG-400 also lessened, but not significantly, the frequency of shivering in irradiated animals. Histopathologic examination of the oral structures demonstrated only marginal protection by PEG-400. Estimation of the alpha/beta ratio from LD50 data on head and neck-irradiated mice yielded values of 4.4 +/- 1.9 (95% confidence limits) Gy without PEG-400 and 7.9 +/- 1.4 Gy with PEG-400. Since it is a non-thiol radioprotector, PEG-400 may be more useful when combined with more conventional thiol-containing radioprotectors.     

Changes in the DNA labelling index after beta irradiation of the mouse epidermis

This study looked at the changes in the interfollicular DNA labelling index (LI) with time after strontium-90/yttrium-90 beta irradiation of approximately 100 mm2 of mouse flank skin, after a dose of 100 Gy which produces transitory moist desquamation. Within 24 hr of such a dose the LI of the irradiated area was essentially zero (0.07 +/- 0.03%), whilst those of the side area and of the control area were 15.0 +/- 2.6% and 21.4 +/- 2.7%, respectively. The LI of the side and the control areas then fell within 3-5 days to approximately 4% and approximately 2% respectively, whilst that of the irradiated area rose rapidly to a peak value of 30.2 +/- 1.7% at 10 days post-irradiation. There was a 20% reduction in the diameter of the area with detectable radiation damage within 5 days, and this is primarily due to cell proliferation and migration from the unirradiated margins of the field. In contrast, between days 10 and 20 the major source of repopulation is probably derived from local migration and proliferation of surviving hair follicle basal cells within the irradiated field.     

The radiosensitivity of kidney colony-forming cells: a short-term assay in situ in the mouse

A short-term colony assay for renal tubule epithelium has been developed. Uranyl nitrate (UN) is a heavy metal nephrotoxin that induces acute tubule necrosis followed by a large compensatory increase in the rate of cell proliferation in the nephron. UN was used to precipitate latent damage following renal irradiation. Using a subcapsular colony count at 14 days after unilateral irradiation, a single-dose cell survival curve was obtained with a D0 of 4.2 +/- 0.3 Gy. High-dose irradiation of an exteriorized kidney resulted in a survival curve which was biphasic, with a plateau in survival between 18 and 40 Gy. Subtraction of this plateau level from all the survival data gave D0 values of 2.5 +/- 0.2 Gy (data analyzed between 7.5 and 16 Gy) or 2.0 +/- 0.2 Gy (over range 12-16 Gy). The D0 value obtained at 20 months after bilateral (or unilateral) kidney irradiation, without the use of UN, was 2.9 +/- 1.1 Gy (over range 10-14 Gy).     

Modifying effect of deep hypoxia on neutron-irradiated mice

Deep hypoxia was shown to influence the survival of animals, the state of the small intestine mucosa and the haemopoietic system. DMF (LD50/30) was 2.49 and 1.66 with X- and neutron radiation, respectively. As to haemopoietic stem cells X-irradiated in vivo, D0 was 0.96 +/- 0.04 Gy (control) and 2.82 +/- 0.14 Gy (anoxia). With neutron irradiation, D0 was 0.44 +/- 0.01 Gy and 0.8 +/- 0.03 for the control and experimental animals respectively.     

Radiation-induced heart disease: morphology, changes in catecholamine synthesis and content, beta-adrenoceptor density, and hemodynamic function in an experimental model.

To study further the pathophysiology of radiation-induced cardiomyopathy, we investigated resting hemodynamics, myocardial catecholamine synthesis and storage, and beta-adrenoceptor density after local heart irradiation. In Wistar rats, a radiation dose of 20 Gy eventually leads to compromised myocardial function which is characterized by a reduction in cardiac output to 43 +/- 11% and in the left ventricular ejection fraction to 66 +/- 7.5%, and an increase in the left ventricular end-diastolic volume to 187 +/- 17% of control values. This reduction in function is correlated with focal degeneration of 23 +/- 4% of the myocardium. Measurement of tyrosine hydroxylase activity and catecholamine content revealed that catecholamine biosynthesis is unchanged in the adrenals but is significantly reduced in the hearts of irradiated animals, while cardiac beta-adrenoceptor density is increased to about 140% of that in age-matched controls. This is in contrast to findings in dilated or ischemic cardiomyopathy. Time-course studies showed that the development of myocardial degeneration starts simultaneously with the decrease in cardiac output and ejection fraction and the increase in beta-adrenoceptors at 50-80 days postirradiation. Myocardial degeneration is maximal in extent and severity at 100 days and does not progress thereafter. Cardiac output decreases at 80-100 days postirradiation to 60 +/- 7% of control values. A significant further decrease is seen only when congestive heart failure becomes manifest at 249 +/- 21 days after 20 Gy. Thus there is a delay between structural myocardial injury and hemodynamic deterioration which could be due to a compensatory increase in beta-adrenoceptor density during the initial stages of the cardiomyopathy.(ABSTRACT TRUNCATED AT 250 WORDS)     

The estimation of the nitric oxide role in the aggravation of combined radiation-thermal injuries

The influence of specific inhibitor of inducible NO synthase S-ethil-isothiourea (as "Difetur" preparation) on liver NO production level, and 30-days survival, mean survival time and probability of mortality within animals under combined radiation/thermal injury (CRTI) were evaluated. Experiments were carrying out on mice (whole body gamma-irradiation at the dose of 7 Gy + 10% body surface full-thickness thermal burn). It was shown, that CRTI induce 2-fold statistical significant increase of NO production in liver of experimental animals. Mice pretreatment with Difetur preparation lead to practically full inhibition of NO production. In the group of animals, with Difetur administration during first two days after CRTI 60% mice survived as compared 15% survive in control group. In pair with data on probability of mortality it was suggested that growth of NO production in the early period of CRTI increase sensitivity of animals to pathological processes leading to death on 10-12 days.     

Manifestation of oxygen effect during normobaric hypoxic hypoxia in the intrauterine and postnatal developmental periods]

The experiments on rats have shown that hypoxic gas mixture containing 10% of oxygen and 90% of nitrogen (HGM-10) under normobaric conditions exerts a highly reliable radioprotective effect on progeny when 11-day pregnant animals are exposed to total irradiation (60Co, 20 Gy). As distinct from the known radioprotector, mexamine, (5-methoxytryptamine), HGM-10 has a pronounced radioprotective effect during the first days (1-5) after birth. Radioresistance of new-born rats correlates with the level of pO2 in the tissues which progressively decreases with respiration of HGM-10 and remains unchanged after mexamine (10 mg/kg) introduction.     

An antifibrotic agent reduces blood pressure in established pulmonary hypertension in the rat

We have shown that administration of the antifibrotic agent cis-4-hydroxy-L-proline (cHyp) to rats at the onset of exposure to hypoxia prevents collagen accumulation in pulmonary arteries and the rise in pulmonary blood pressure. In this experiment, we tested whether cHyp is effective when administered after hypertension was already established. Rats were exposed to hypoxia (10% O2) for 21 days. Groups were hypoxic animals treated with cHyp (200 mg/kg sc twice daily) on days 10-21 (hypoxic cHyp) and saline-injected hypoxic animals (hypoxic). On day 21, we measured mean right ventricular pressure, hematocrit, collagen content of main and intrapulmonary arteries, and wall thickness of arterioles. Treatment reduced right ventricular pressure from 21 +/- 1 to 17 +/- 1 mmHg (P less than 0.05), hematocrit from 66 +/- 1 to 56 +/- 1% (P less than 0.05), hydroxyproline content of intrapulmonary arteries from 30 +/- 3 to 11 +/- 2 micrograms/vessel (P less than 0.05), and wall thickness from 27 +/- 3 to 16 +/- 2 microns (P less than 0.05). These results show that vascular collagen content is increased in established pulmonary hypertension and that cHyp treatment is effective in partially preventing the hemodynamic, structural, and biochemical changes if started after pulmonary hypertension is established. cHyp may also affect the rheological properties of blood.     

Cyclosporine A dosing-time-dependent effects on plasma creatinine and body weight in male Wistar rats treated for 3 weeks.

Cyclosporine A (CsA) nephrotoxicity was assessed in 120 male Wistar rats (350 +/- 50 g) entrained to a 12-h cycle (light-dark 12:12); plasma creatinine level and body weight were examined in controls and in rats that had been treated daily with oral CsA or vehicle alone (olive oil-ethanol 90:10) for 21 days; daily dosing (40 mg/kg) was at one of six equally spaced given times during the 24-h cycle. The variations observed in both indexes were shown to be circadian dosing stage dependent. Nephrotoxicity was present as early as the third day of treatment with CsA; plasma creatinine level was enhanced by about 50% in rats dosed around the time of the change from darkness to light: at 22 HALO, 146.7 +/- 4.5 mumol/L, against 92.0 +/- 2.8 mumol/L for controls (p less than 0.05); and at 2 HALO, 148.3 +/- 10.0 mumol/L, against 95.0 +/- 4.3 mumol/L for controls (p less than 0.05). Thereafter, a remission episode was observed between days D5-D9. The more drastic effects were seen on days D16 and D21, in animals dosed in the beginning of the dark span (14 HALO): 185 +/- 10 mumol/L for CsA and 98.0 +/- 5.3 mumol/L for controls (p less than 0.01) and, to a lesser extent, in rats treated at the early resting phase (2 HALO): 152.4 +/- 31 mumol/L for CsA and 95.0 +/- 4 mumol/L for controls (p less than 0.05). The normal increase in body weight during the 21-day period (about 14 +/- 8% in controls) was impeded in CsA-administered rats, especially those dosed at the beginning of the activity span (14 HALO) that even suffered weight reduction. Differences in percentages of survivors were noticed, depending on dosing stage. About 40% of the animals in every time CsA-treatment group died, except for those dosed at the end of the resting period (10 HALO), when all animals died. In surviving rats, the cessation of CsA dosing resulted in a reversible effect on the study variables.     

Life shortening and disease incidence in BALB/c mice following a single d(50)-Be neutron or gamma exposure

Male BALB/c mice, 12 weeks old, were given a single exposure of either 137Cs gamma rays or d(50)-Be neutrons at a dose rate of 3 Gy/min. The animals were kept until death, and causes of death or possible causes of death were ascertained by autopsy and histology. The data were evaluated by competing risk methods. The survival time dose-effect curve for both types of exposure was linear and did not differ significantly (slopes: 55.8 +/- 4.0 days/Gy for neutrons and 46.2 +/- 4.3 days/Gy for gamma rays). The incidence of different diseases also was similar for both groups except that more carcinomas, sarcomas, and myeloid leukemias seemed to occur after neutron exposure and that nonstochastic lung and kidney diseases seemed to arise at lower doses.