Alterations in ribonucleic acid synthesis by chromium (III)

Body condition, energy balance and immune status of periparturient Murrah buffaloes (Bubalus bubalis) supplemented with inorganic chromium

Periparturient Murrah buffaloes were used to determine whether body condition, energy balance and immune status are affected by inorganic Cr supplementation. Twenty-four Murrah buffaloes were blocked into four groups having six animals in each group and fed for 60 days pre-partum to 150 days post-partum. Feeding regimen was same in all the groups except that these were supplemented with 0.0, 0.5, 1.0 and 1.5 of Cr per kilogram of dry matter (DM) in the four respective groups. Buffaloes were weighed at fortnightly intervals. Blood samples were collected from the jugular vein at days -60, -30, -15, -7, 0, 7, 15, 30, 60, 90, 120 and 150 of experimental feeding for the estimation of non-esterified fatty acid (NEFA), beta-hydroxybutyric acid (BHBA), Cr level, lymphocyte proliferation, neutrophil phagocytic activity, plasma total immunoglobulin (TIg), immunoglobulin G (IgG) and cortisol levels. Results revealed that with approaching parturition, dry matter intake (DMI), immune response and plasma Cr level decreased (P < 0.05) gradually and minimum values were observed on the day of parturition in all groups. In contrast, body condition score (BCS), plasma NEFA and BHBA concentrations showed increasing (P < 0.05) trends towards calving and level decreased after calving. Dietary Cr supplementation did not have any effect on DMI and BCS, but immune response and plasma Cr concentration showed a positive correlation with dietary Cr supplementation. Buffaloes supplemented with 1.5 mg/kg Cr had significantly (P < 0.05) low plasma NEFA and BHBA concentrations. The results of present findings indicated that dietary inorganic Cr supplementation reduced lipid mobilization and improved immune response in periparturient buffaloes.

Study of hematological indices in tannery workers exposed to chromium in Sheikhupura (Pakistan)

Chromium (Cr), being an excellent tanning agent, is widely used in the leather industry and tannery workers (TW) are exposed to it either in the form of inorganic Cr(III) compounds or Cr bound to proteins (leather dust) in the process of leather production. During the present study, the effect of Cr on the hematological indices in TW was evaluated. In this study, hematological indices of 92 male TW aged 20—60 years were compared with 79 control males who hardly had a chance of exposure to chromium. Both groups were subdivided into four age groups with an interval of 10: group A, 20—29 years; group B, 30—39 years; group C, 40—49 years; group D, 50—60 years. Total erythrocyte count (TEC) was significantly lower (p < 0.05) in TW of age group A, B and C than control subjects. Packed cell volume (PCV) was significantly higher (p < 0.05) in TW of age group B while mean corpuscular hemoglobin (MCH) was significantly lower (p < 0.05) in TW of age group D. Within the TW, MCH was significantly lower (p < 0.05) in the age group D as compared to age group A and B. No significant changes were observed in the values of hemoglobin, mean corpuscular volume and mean corpuscular hemoglobin concentration between TW and control individuals. The low values of TEC, PCV and MCH might be a result of chromium exposure in the tannery workers and may act as indicators of chromium toxicity.

Mechanisms of chromium-induced suppression of RNA synthesis in cellular and cell-free systems: relationship to RNA polymerase arrest

Chromium(VI) (Cr(VI)) can suppress both DNA replication and transcription as a result of chromium (Cr)-induced DNA damage. While progress has been made in the characterization of Cr-induced DNA polymerase arresting lesions, very little information is available on the inhibition of transcription by this metal. The aim of the present study was to identify the molecular mechanisms involved in the reduction of RNA synthesis by Cr. Following treatment with a moderately cytotoxic dose (approximately LC50) of Cr(VI) (150 microM for 2 h), total RNA synthesis was initially suppressed in CHO cells and recovered to control levels within 72 h post-treatment. In vitro nuclear run-on transcription assays of nuclei isolated from Cr(VI)-treated cells showed a similar amount of RNA synthesis suppression as observed in intact cells. Qualitative analysis of nascent transcripts revealed a general, concentration-dependent reduction in size suggesting that transcriptional elongation was inhibited following Cr-treatment. Transcriptional initiation in these nuclei was also reduced. To better determine whether transcriptional suppression was related to Cr-induced DNA damage we examined the transcriptional activity of T7 RNA polymerase on Cr(III)-treated plasmid DNA. Treatment of pGEM3Z-TS DNA with Cr(III) resulted in transcriptional arrest which occurred primarily at GC-rich and palindromic regions. However, in contrast to the cellular data, transcriptional initiation was unaffected in the in vitro transcription arrest assays. Taken together, these results suggest that the suppression of RNA synthesis by Cr is related to chromium-induced template DNA damage which prevents elongation leading to premature RNA polymerase arrest.

Immune response and disease resistance of calves fed chromium nicotinic acid complex or chromium chloride

Twenty-one Holstein bull calves (< 7 d of age at the initiation of the experiment) fed a milk replacer diet were used to assess the effects of supplemental Cr on immune response. Treatments consisted of milk replacer without supplemental Cr (control) or milk replacer with 0.4 ppm of supplemental Cr from CrCl3 or a Cr-nicotinic acid complex. On d 64, increases in skinfold thickness after an intradermal injection of phytohemagglutinin were measured to evaluate cell-mediated immune response. Calves supplemented with Cr-nicotinic acid complex had a greater response than did controls at 6, 12, 24, and 48 h after injection. Calves supplemented with CrCl3 had a greater response than did controls at 24 and 48 h after injection. In vitro blastogenic responses of lymphocytes to phytohemagglutinin or pokeweed mitogen and antibody response to porcine red blood cells were not affected by treatment. Following a disease challenge with an intranasal dose of infectious bovine rhinotracheitis on d 75, body temperature tended to be lower for calves supplemented with Cr-nicotinic acid complex than for control calves. Calves supplemented with either Cr source had lower serum cortisol concentrations at 5 d after challenge. Chromium supplementation enhanced cell-mediated immune function.

Effects of chromium on health status, blood neutrophil phagocytosis and in vitro lymphocyte blastogenesis of dairy cows

The objective of this study was to determine the effects of supplemental dietary chromium (Cr) on health status and mastitis-related parameters, as well as neutrophil phagocytic activity of dairy cows during late pregnancy and early lactation. In addition, possible interactions and involvements of Cr with insulin, cortisol, somatotropin (rBST) and insulin-like growth factor-1 (IGF-1) were directly investigated in vitro based on blastogenic responses using peripheral blood lymphocytes (PBL) of eight cows fed the control diet. Forty pregnant Holsteins, 18 primiparous and 22 multiparous, at week (wk) 6 before the expected calving dates were randomly assigned to treatments: control and supplemental chelated Cr (0.5 ppm) in the diet. All cows were managed in a normal production operation and health status was assessed by recording the incidence of health problems during the experimental period of wks 6 before and 16 after calving (-6 to 16 wks). Mastitis-related parameters included somatic cell counts (SCC), bacterial colony counts of milk samples from each mammary gland quarter of all cows during wk 1 to wk 8 postpartum. Peripheral blood neutrophil phagocytic function of eight cows fed either control or supplemental Cr diet was determined by the ability to take up uniform fluorescent beads measured by flow cytometry. Supplemental Cr had no effect (P > 0.10) on health status of cows during late pregnancy and early lactation, or on SCC and bacterial colonies of quarter milk samples from early lactation (wks 1 to 8). Supplemental Cr also did not affect neutrophil phagocytic function of cows from 6 wks prepartum to 6 wks postpartum. However, in the in vitro study of PBL (from control animals, not fed Cr diet) blastogenesis with addition of insulin or cortisol at two levels (0.05 and 0.5 ng ml-1), insulin and cortisol enhanced or had no effect on PBL proliferations with or without concanavalin A (con A) simulation. However, further Cr addition in the culture medium containing supplemental insulin or cortisol, particularly CrCl3, additively increased (P < 0.05) BPL blastogenic activities with or without con a stimulation. Conversely, addition of rBST or IFG-1 (0.5 and 5.0 ng ml-1) in the culture medium enhanced PBL proliferation, but addition of Cr gave no additional effect. These results indicated that supplemental Cr had no beneficial effect on health status, mastitis-related parameters or neutrophil phagocytic activity of dairy cows. However, in vitro study confirmed and extended our previous observations that Cr has an effect on lymphocyte proliferation and this may associate with insulin or cortisol actions.

Enhancement of nucleolar RNA synthesis by chromium (III) in regenerating rat liver

Rats pretreated with CrCl3 at an intraperitoneal dose of 5 mg Cr/kg body weight, and then subjected to partial hepatectomy concentrated Cr in the regenerating liver cells, especially in the nucleoli. Hepatic RNA synthesis induced by partial hepatectomy was further enhanced by Cr(III) administration without changes of the nucleotide pool size at least for 12 hr after the hepatectomy. Of the RNA species newly synthesized, the synthesis of nucleolar RNA was predominantly enhanced. The nucleolar RNA thus synthesized in the regenerating liver of Cr(III)-dosed rats followed normal processing into rRNA as estimated by actinomycin D-chase experiments followed by sucrose density gradient centrifugation analysis and also by nucleotide composition analysis of nucleolar and ribosomal RNAs. These results suggest that Cr accumulated in nucleoli may participate in nucleolar gene expression.

In vitro assessment of the toxicity of metal compounds : IV. Disposition of metals in cells: Interactions with membranes, glutathione, metallothionein, and DNA

This review has focused on several parameters related to the delivery of carcinogenic metal compounds to the cell nucleus as a basis for understanding the intermediates formed between metals and cellular components and the effect of these intermediates on DNA structure and function. Emphasis has been placed on metal interactions at the cellular membrane, including lipid peroxidation, metal interactions with glutathione and their relation to membrane injury, and metal effects on the membrane bound enzyme, Na(+)/K(+) ATPase. Metal binding to metallothionein is also considered, particularly as related to transport and utilization of metal ions and to genetic defects in these processes exemplified in Menkes disease. The ability of cadmium to induce the synthesis of metallothionein more strongly than zinc is also discussed in relation to other toxic and carcinogenic metals. The effects of metal ions on purified DNA and RNA polymerase systems are presented with some of the recent studies using biological ligand-metal complexes. This review points out the importance of considering how metals affect in vitro systems when presented as ionic forms or complexed to relevant biological ligands.

Enhancement of ribonucleic acid synthesis by chromium(III) in mouse liver

The effect of Cr(III) administration on hepatic RNA synthesis in mice was studied. It was found that Cr accumulated in mouse liver. Forty-eight hours after intraperitoneal injection of CrCl3 (0.005-5 mg Cr/kg body weight) approximately 10% of the administered dose per g of tissue remained. The accumulated Cr was still retained 64 days after administration (5 mg Cr/kg) with only a slight decrease. Approximately 20% of the hepatic Cr was detected in the nuclei. By administering CrCl3. RNA synthesis in mouse liver was markedly enhanced without altering the pool size of nucleotides. This enhancement was dose-dependent and statistically significant at doses of 0.05 (p less than 0.05), 0.5 (p less than 0.01), and 5 mg Cr/kg (p less than 0.01), and remained so for at least 16 days after administration of 5 mg Cr/kg. The synthesis of DNA and protein in mouse liver were not significantly changed by CrCl3 administration. On the other hand, Cr(VI) administration did not enhance but rather inhibited RNA synthesis in mouse liver. These results suggest that Cr(III) specifically enhances RNA synthesis in mouse liver.