Intratracheal exposure of the guinea pig lung to cadmium and/or selenium: a histological evaluation.

Anesthetized male Hartley guinea pigs (350-410 g) (n=5) received intratracheally, saline; cadmium (Cd) (0.3 mg); selenium (Se) (0.3 or 0.06 mg); or Cd (0.3 mg) with Se (0.06 mg), per animal. Twenty-four hours later, lungs were evaluated. Bronchoalveolar-lavage fluid of Cd- and/or Se-treated animals varied in their total and differential leukocyte percent population from that of saline control (P<0.05). Cadmium alone or with Se caused high lung to body weight ratios (P<0.05). High lung wet-weight to dry-weight (W/D) ratios (P<0.05) suggestive of lung edema, were evident after Cd and/or Se exposure. Histological examination of Cd- and/or Se-exposed lungs revealed leukocytic infiltration. Results demonstrated that separate or concurrent exposure to noxious metal(s) such as Cd and Se provoke lung edema and injury. Low dose of Se which when instilled alone, although did not result in an increased W/D lung ratio, failed to subside concurrently administered Cd-inflicted damage.

An acute intratracheal selenium study: immediate effects on respiration in guinea pigs.

Pulmonary function was assessed in non-sensitized male guinea pigs (206-445 g) before and after intratracheal (ITr) treatment with saline or selenium (Se, 0.06 mg/100 g body weight) as selenium dioxide (SeO2) or seleno-L-methionine (SeM). Pulmonary functional parameters such as the respiratory rate (f), tidal volume (TV), dynamic lung compliance (Cdynl) and lung resistance (Rl) were determined using the respiratory flow (F) signal and the transpulmonary signal obtained via the intrapleural pressure (P) from the animal. Although, pulmonary dysfunction was observable with exposure to two different Se compounds, the SeO2-induced changes in f and Rl were significant (P < 0.05). Treatment with SeM did not result in alteration of any of the parameters significantly. Results indicated that acute ITr SeO2 exposure affects respiration precipitated by a significantly decreased f and an increased Rl unlike after SeM. The Cdynl did not change significantly after treatment with either of the two Se compounds. Comparing the immediate effects of the two different Se compounds on respiration, acute ITr SeO2 exposure was found to be more detrimental to pulmonary function than SeM.

Guinea pig pulmonary mechanics: altered sensitivity to carbachol by cadmium and/or selenium.

Male Hartley guinea pigs (480-610 g) were treated intratracheally as follows: saline, cadmium (Cd, 0.3 mg), selenium (Se, 0.3 or 0.06 mg), or Se (0.06 mg) and Cd (0.3 mg) simultaneously. Selenium and Cd were administered as sodium selenite and cadmium chloride, respectively. Twenty-four h later, dynamic lung compliance (Cdyn) and pulmonary resistance (Rp) were measured before (baseline Cdyn and Rp) and after carbachol administration (0.0001, 0.001, 0.01, and 0.1 mumol/kg, intravenously). Results indicated a significant decrease in baseline Cdyn caused by 0.3 mg of Cd, 0.3 mg or 0.06 mg of Se, and 0.3 mg of Cd with 0.06 mg of Se (p < 0.05). A significant increase in baseline Rp due to 0.3 mg of Se was observed (p < 0.05). Carbachol decreased Cdyn significantly below baseline, evident after lower doses of carbachol, in guinea pigs pretreated with 0.3 mg of Se, whereas a significant improvement in Cdyn was seen after 0.0001 mumol/kg carbachol in the group pretreated with Se and Cd simultaneously (p < 0.05) compared with the respective baseline values of the saline-treated group. Similarly, a significant increase in Rp was observed after carbachol in groups pretreated with 0.3 mg of Cd or Se (p < 0.05). Results also indicated a significant increase in large airway constriction caused by Cd and/or Se (p < 0.05). A leftward shift in the carbachol dose-response curve indicated increased sensitivity to carbachol in Cd- and/or Sepretreated guinea pigs.

Cadmium and/or selenium effects on guinea pig lung PGE2, TXB2 and LTC4.

Male Hartley guinea pigs (480-610 g; n=5) were treated intratracheally with saline, cadmium (Cd, 0.3 mg) as cadmium chloride, selenium (Se, 0.3 or 0.06 mg) as sodium selenite or Se (0.06 mg) and Cd (0.3 mg). After 24 hours, lungs were collected and analyzed for prostaglandin (PGE2), thromboxane (TXB2) and leukotriene (LTC4) levels. Results indicated that, 0.3 mg Se and 0.06 mg Se in combination with 0.3 mg Cd increased PGE2 significantly. Selenium and Cd alone or in combination, decreased LTC4 and TXB2 significantly.

Selenium and cadmium induced pulmonary functional impairment and cytotoxicity.

Ovalbumin-sensitized (50 mg/kg, i.p.) male Hartley-guinea-pigs (550-610 g; n = 6) were treated 14 days later intratracheally with saline, cadmium (Cd 0.3 mg), selenium (Se 0.3 mg or 0.06 mg) or Se (0.06 mg) with Cd (0.3 mg). After 24 h, baseline dynamic-lung-compliance (Cdynl) and pulmonary-resistance (Rp), and percent change after ovalbumin-aerosol-challenge (10 mg/ml, 60 s) were assessed. Cadmium or Se (0.3 mg), Se (0.06 mg) and/or Cd (0.3 mg) decreased Cdynl (P < 0.05). Selenium (0.3 mg) increased Rp (P < 0.05). Ovalbumin-challenge decreased Cdynl and increased Rp in all groups. Analysis of bronchoalveolar-lavage-fluid (BALF) displayed increased activities of lactate-dehydrogenase (LDH), beta-glucuronidase (beta-G), alkaline-phosphatase (AP), and protein due to 0.3 mg Se, 0.3 mg Cd alone or with 0.06 mg Se (P < 0.05). Findings indicated that, 0.3 mg Se is more detrimental than 0.3 mg Cd to lung-dynamics despite a modest protection by 0.06 mg Se against Cd illustrated by an ameliorated Cdynl and lower protein in BALF.

In vivo response of the normal and regenerating adrenal glands to thyroid manipulation in rats.

Adrenal corticosterone (CORT) levels and ornithine decarboxylase (ODC) activities in thyroid intact, thyroidectomized, and thyroxine (2 micrograms/ml in drinking water for 3 weeks) supplemented rats were measured 11 days after adrenal sham surgery or enucleation. Thyroidectomy decreased and thyroxine supplementation increased adrenal CORT significantly (p < 0.05) at 0600 h and 1800 h. The ODC activity was not significantly affected by thyroidectomy. Thyroxine supplementation however, inhibited ODC activity significantly (p < 0.05) at 1800 h in the regenerating adrenal cortex. Results indicated that, while CORT response in normal and regenerating adrenals are positively related to thyroid manipulation, inhibition of adrenal ODC activity by thyroxine may affect adrenal regeneration.

Inhibition of the rat adrenal ornithine decarboxylase activity by immobilization stress and/or dexamethasone.

The effects of immobilization stress and/or dexamethasone (DEX) on the adrenal ornithine decarboxylase (ODC) activities of sham-operated and adrenal-medulloectomized (enucleated) male Sprague-Dawley rats were investigated. On day 11 after surgery, rats were injected with saline or DEX (1 mg/kg), 3 h before the time of sacrifice (0600 h or 1800 h). Four groups, from sham-operated and enucleated rats (ENU) treated with saline or DEX were subjected to immobilization stress for 1 h prior to sacrifice. Groups of rats from stress-sham-DEX, non stress-sham-DEX, stress-sham, non stress-sham, stress-ENU-DEX, non stress-ENU-DEX, stress-ENU, and non stress-ENU were sacrificed at 0600 h or 1800 h on day 11 after surgery. Adrenal glands were excised and later analyzed for ODC activities. Results indicated that DEX and/or immobilization stress inhibited ODC activities (p<0.05) in normal and regenerating adrenal glands at 1800 h and ODC activity varies diurnally, the activity being greater at 1800 h than at 0600 hours (p<0.001).

Subacute exposure to cadmium chloride induces HSP-72 in rat liver.

Two groups of rats (n = 5) weighing 175-185 g were implanted (sc) with osmotic minipumps to deliver (0.5 microliter/hr) deionized water or cadmium chloride (CdCl2; 0.2 M) for 14 days. On completion of subacute treatment, liver and kidneys were collected from control and CdCl2 treated groups for analysis. We report that, subacute exposure to CdCl2 results in significant Cd accumulation in liver and kidneys, and heat-shock-protein 72 (HSP-72) induction in the liver. Results affirm a role for liver HSP-72 in Cd-toxicity.

Decreased endurance to cold water swimming and delayed sexual maturity in the rat following neonatal lead exposure.

The effects of neonatal lead (Pb) exposure on ability to endure stress and on the onset of sexual maturity were investigated using rats. Sprague-Dawley dams (n = 17/treatment) were treated with or without lead acetate (0.3%) in drinking water from parturition until postnatal day (PND) 21, at which time the pups were weaned. A set of sex-balanced pairs of pups (24 male and 24 females/treatment) from randomly selected control and Pb-treated dams was tested for cold water (4 degrees C) swimming-endurance on PND 15, 21, 25 and 30. Lead treated-female pups showed significantly (P < 0.05) lower endurance on PND 21 and 30, while Pb-treated males exhibited lower (P < 0.05) endurance on PND 21 compared to their respective controls. The results of this study indicate that neonatal exposure to Pb decreased cold water swimming-endurance. Neonatal exposure to either Pb or swimming stress delayed (P < 0.002) the onset of sexual maturity in both sexes. However, exposure to both treatments masked the effect of swimming stress on the onset of maturity in females but not in males.

Effect of selenium (Se) on plasma ACTH, beta-endorphin, corticosterone and glucose in rat: influence of adrenal enucleation and metyrapone pretreatment.

The effects of acute treatment (i.p.) with selenium (Se) on glucoregulation, by measuring plasma levels of adrenocorticotropic hormone (ACTH), beta-endorphin (beta-EN), corticosterone (CORT) and glucose over time, were investigated. The hormones of the hypothalamic-pituitary adrenal (HPA) axis, were measured after treating rats with saline, Se: 1.6 mg/kg, or 3.8 mg/kg. Blood samples were collected before, 30, 60 and 90 min following injection. The results show that i.p. administration of Se (both doses) induce a rise in plasma ACTH, and beta-EN (P < 0.01). Plasma CORT and glucose levels also rose sharply by 30 min (P < 0.05). Corticosterone levels were increased in a dose-dependent fashion over the ensuing hour. Bilateral adrenal demedullation resulted in the abolishment of the Se-induced rise in plasma glucose. Pretreatment with metyrapone (300 mg/kg) was found to delay the Se-induced rise in plasma glucose. The results indicate that after a Se challenge the HPA axis is activated. In addition, CORT was found to be essential in the Se-induced rise in plasma glucose.

Selenium lethality: role of glutathione and metallothionein.

Male Sprague-Dawley rats (200-300 g) were pretreated (i.p.) with diethylmaleate (DEM; 3.1 mmol/kg) or propylene glycol (PG). After 1 h, three PG and three DEM groups received saline or sodium selenite (Se: 0.8 or 1.6 mg/kg) i.p. Eighty to one hundred percent mortality occurred within 3 h after Se in DEM-pretreated groups. Except for one PG and one DEM group, which were sacrificed after 1 h, the remaining groups received saline or Se (1.6 mg/kg) 25 h after pretreatment. No mortality occurred within 3 h after Se. Liver and kidney GSH decreased at 1 h, while liver MT increased at 28 h. The changes are related to Se-induced lethality.

Effect of cadmium and/or selenium on liver mitochondria and rough endoplasmic reticulum in the rat.

This study was conducted to investigate the effect of cadmium (Cd) and/or selenium (Se) on hepatic mitochondria and rough endoplasmic reticulum (RER). Male Sprague Dawley derived rats (150-200 g) received sodium acetate (NaAc; 1.23 mg/kg), Cd (0.84 mg/kg), and/or Se (1.6 mg/kg) intraperitoneally. Livers were perfused with 2% glutaraldehyde at 48 h, 72 h, or 96 h after treatment and prepared for electronmicroscopy. Results indicate that Cd and/or Se are capable of inflicting mitochondrial and RER structural changes, and the damage by Cd alone is more severe than Se alone or with Cd.

Effect of selenium on plasma glucose of rats: role of insulin and glucocorticoids.

The effects of acute treatment (i.p.) of selenium (Se) on glucoregulation and on plasma levels of glucose, insulin and corticosterone were determined in both fed and 24-hour-fasted rats. In this experiment animals were treated with saline (control) or 1.3, 1.6 and 3.8 mg/kg doses of Se. Blood samples were collected before, 30, 60 and 90 min following injection. The results obtained show that acute intraperitoneal (i.p.) administration of Se (1.6 mg/kg or more) causes hyperglycemia in rats. It was found that Se does not change levels of plasma insulin in either fasted or fed animals. Se did, however, significantly increase the plasma levels of corticosterone in all Se-treated groups. In order to confirm the role of corticosterone and thus support the significance of adrenal glands in this hyperglycemic response, animals were subjected to bilateral adrenalectomy. Blood samples were collected before, 30, 60 and 90 min following intraperitoneal treatment with Se. The results indicate that bilateral adrenalectomy abolishes the hyperglycemic response to Se. It can be concluded that adrenal glands play a role in Se-induced hyperglycemia. The increase in corticosterone levels suggest the possibility of gluconeogenesis in contributing to this hyperglycemic response.

Effect of in vitro treatment of rat hepatocytes with selenium, and/or cadmium on cell viability, glucose output, and cellular glutathione.

The effects of cadmium as cadmium acetate and selenium as sodium selenite on glucose output, cell viability, and glutathione levels in rat hepatocytes were evaluated. Isolated hepatocytes (200 mg wet wt cells) derived from naive male Sprague--Dawley rats (210-260 g) were incubated at 37 degrees C, with sodium acetate (C2H3NaO2; NaAc) 12.5 microM, 6.3 microM, 3.2 microM; cadmium acetate (C4H6CdO4; Cd) 12.5 microM, 6.3 microM, 3.2 microM; sodium selenite (Na2SeO3; Se) 25 microM, 12.5 microM, 6.3 microM; or Se (6.3 microM) and Cd (3.2 microM). After an incubation period of 2 h, glucose output, cell viability, and reduced glutathione (GSH) levels were determined. The results obtained indicate that incubation of hepatocytes with Se (12.5 or 25 microM) or Cd (3.2, 6.3, or 12.5 microM) resulted in a significant decrease in glucose output, cell viability, and glutathione levels (P less than 0.05) when compared to those incubated with NaAc (control). Selenium in concentrations of 6.3 microM decreased glutathione levels and cell viability only. The damaging effects induced by Cd on hepatocytes were significantly greater than those induced by Se. The decrease in glutathione levels observed following Cd treatment was considerably lowered when Se was concurrently added to the incubation medium. These findings suggest that Se may in part protect against the deleterious effects of Cd on hepatocytes.

Effect of cadmium on blood glucose level in the rat.

The purpose of this study was to determine the effect of cadmium (Cd) or Cd and selenium (Se) administered simultaneously on plasma glucose level. Male Sprague-Dawley derived rats (180-300 g), maintained under controlled environmental conditions, were segregated into fed and 24-h fasted groups prior to experimentation. Each group consisted of 3 subgroups which received one of the following treatments intraperitoneally: sodium acetate (NaAc) (1.23 mg/kg), Cd (0.84 mg/kg) or a combination of Se and Cd (1.6 and 0.84 mg/kg respectively). Plasma glucose was measured before and 30, 60, 120, 180, 240, 300 or 360 min after treatment. Results indicate that both Cd and concurrent administration of Se and Cd induce hyperglycemia in fed and fasted rats.

Feeding elicited by 2-deoxyglucose occurs in the absence of reduced glucose oxidation.

We have previously reported that feeding in response to either systemic or intracerebroventricular administration of 2-deoxy-D-glucose (2-DG) persists for at least 6--8 h post-2-DG injection when the sympathoadrenal hyperglycemic response to glucoprivation has abated. This delayed feeding response to 2-DG suggests either that ongoing glucoprivation is not necessary for feeding or that responses such as hyperglycemia abate while glucoprivation is still extant and able to stimulate feeding. In order to determine whether glucoprivation is still present after the sympathoadrenal hyperglycemic response to 2-DG has abated, we measured systemic 14CO2 evolution and glucose oxidation in Sprague-Dawley rats treated with 2-DG (200 mg/kg) 0.5 and 6 h earlier. In addition, we measured cerebral 14C-2-DG accumulation in rats treated with unlabelled 2-DG 6 h prior to tracer administration We found that 14CO2 evolution and glucose oxidation were reduced by 47 and 667%, respectively, during the first 3.5 h post-2-DG but were normal by 6 h post-2-DG. Furthermore, we found that the uptake of 14C-2-DG into the brain was not diminished between 6 and 7 h after administration of unlabelled 2-DG. These results suggest that ongoing reduction of systemic glucose oxidation and ongoing impairment of hexose availability to the brain need not occur during 2-DG-induced feeding.