Anti-oxidant supplementation decreases TBA reactants in serum of elderly

An “anti-oxidant cocktail” consisting of betacarotene, vitamins B₆, C, E, zinc, and selenium or corresponding placebos were given for one y as daily dietary supplements to 45 elderly residents of a nursing home. Initially, the serum TBA reactant levels were higher (2.7±0.7 μmol/L) than those of an ad hoc control group of healthy younger adults (2.3±0.6 μmol/L),p<0.01. After three mo supplementation, the levels among the verum elderly had decreased to 2.2±0.6 μmol/L, and they remained at this lower level until the end of the study period, whereas the placebo group showed no change. A significant inverse correlation (r=−0.428,p<0.01) existed between the concentrations of serum TBA reactants and whole blood selenium (B-Se), but only B-Se levels above 200 μg/L were associated with a decrease in serum lipid peroxides. Serum alpha-tocopherol concentration also correlated inversely with serum TBA reactants but this correlation (r=−0.273,p<0.76) was not as strong as that of B-Se. Deficient vitamin B₆ status, in biochemical terms, was observed in 25% of the elderly; a daily supplement of 2 mg B₆ fully cured all cases of deficiency. The verum group improved slightly in several psychological tests, whereas subjects on placebo remained unchanged or deteriorated during the follow-up period. Clinical amelioration among the verum subjects was reported by the nurses; no toxic side effects were reported. In conclusion, the elderly benefited biochemically and clinically of dietary antioxidant supplements.     

Levels of selenium in plasma and glutathione peroxidase in erythrocytes and the risk of breast cancer

Plasma selenium and glutathione peroxidase in erythrocytes were analyzed in a case-control study encompassing 441 cases with breast cancer and 191 controls with benign breast disease. No difference in mean serum selenium level between cases and controls on supplementary selenium intake was seen. If only individuals without supplementary intake, 278 cases and 135 controls, were considered a preventive effect was found increasing with selenium level. This finding was significant among women 50 years old or more with Mantel-Haenszel odds ratio=0.16 for individuals with serum selenium >1.21 μmol/L. Also for subjects with serum selenium in the range 1.00–1.21 μmol/L a significant preventive effect was seen with odds ratio=0.38. For women under 50 years of age a nonsignificant preventive effect was seen. Glutathione peroxidase in erythrocytes did not correlate well with serum selenium and was not a marker for the risk of breast cancer.     

Concentrations of cadmium,lead, selenium,and zinc in human blood and seminal plasma

The concentrations of cadmium, lead, selenium, and zinc in blood and seminal plasma were determined in 76 Singapore males. Except for zinc, the concentrations were generally higher in blood than in seminal plasma (cadmium, 1.31 μg/L vs 0.61 μg/L; lead, 82.6 μg/L vs 12.4 μg/L, and selenium, 163.6 μg/L vs 71.5 μg/L). The mean concentration of zinc in seminal plasma was more than 30 times higher than in blood (202 mg/L vs 6.2 mg/L). Significant positive correlations were found between the concentrations in blood and seminal plasma for the two essential trace elements: selenium (r=0.45,p<0.001) and zinc (r=0.25,p<0.05). However, no relationships were found between the concentrations in blood and seminal plasma for two toxic metals (cadmium and lead). Significant inverse correlations were observed between Cd and Zn (r=−0.40,p<0.01), and Pb and Se (r=−0.32,p<0.05) in blood, whereas significant positive correlations were noted between Cd and Se (r=0.45,p<0.01), Cd and Zn (r=0.35,p<0.05), and Se and Zn (r=0.57,p<0.001) in seminal plasma. The physiological significance of these relationships are also discussed in this paper.     

Effects of diabetes type and treatment on zinc status in diabetes mellitus

Zinc status was assessed in 53 diabetic patients: 18 insulin-dependent diabetic patients (IDDM), 22 noninsulin-dependent diabetic patients (NIDDM) treated with oral antidiabetic agents, and 13 insulin-treated, noninsulin-dependent diabetic patients (IRDM). Plasma zinc concentrations were in the usual range for healthy subjects in these three groups (15.3±0.9 μmol/L). Urinary zinc excretions were elevated in the IDDM group (18.3±4.1 μmol/24 h;p<0.01 vs normal) and in the NIDDM group (17.5±3.5 μmol/24 h;p<0.01 vs normal), but normal in the IRDM group (11.3±2.4 μmol/24 h). In 14 NIDDM patients treated with transient continuous sc insulin injections, urinary zinc decreased from 16.5±2.2 μmol/24 h before insulin treatment to 11.5±0.3 μmol/24 h after insulin treatment without any modification in plasma zinc concentrations.     

Significance of serum trace element status in patients with rheumatic heart disease

It is known that certain trace elements can affect various heart diseases. In this study, we aimed to evaluate the changes in concentrations of certain serum trace elements in patients with chronic rheumatic heart disease (RHD). Serum analysis of selenium (Se), zinc (Zn), and copper (Cu) trace elements was assayed by atomic absorption spectrophotometry. RHD patients had significantly lower serum concentrations of Se and Zn than control subjects (p<0.05 and p<0.001, respectively). However, the serum Cu concentration was significantly higher in RHD patients than in controls (1.93±0.59 μg/L vs 1.06±0.29 μg/L; p<0.001). Similarly, the Cu/Zn ratio in RHD patients was higher than in control subjects (4.70±0.92 vs 1.68±0.45; p<0.001). Additionally, no significant correlation was found among these trace element concentrations and the functional capacity classes (p>0.05). RHD patients had decreased serum Se and Zn element concentrations and increased serum Cu element concentration. We suggest that Se and Zn deficiency might be contributory factors in the development of rheumatic heart disease, and a high Cu concentration and a high Cu/Zn ratio might reflect an ongoing inflammatory process in this disease.     

Serum selenium levels in diabetic children

The effect of increased selenium uptake on serum selenium in diabetic children was investigated during the first 9 yr of the Finnish nationwide selenium fertilization program, which started in 1984. Serum selenium concentrations were followed in 237 diabetic children (mean age 8.1 yr) and 214 controls from 1984 to 1992. The control group consisted of 107 siblings of the diabetics and of 107 other healthy children of corresponding age groups. Selenium was determined by direct electrothermal atomic absorption spectrophotometry. The effect of the increased uptake was seen in both diabetic and in control persons. Before the autumn of 1985, diabetic patients had significantly higher serum selenium levels than their siblings or the other healthy controls. Toward the end of year 1987, this difference had disappeared. After that, serum selenium levels continued to increase until the year 1990. In 1990 the mean selenium serum level of diabetic patients was 1.36 μmol/L and that of controls 1.33 μmol/L. The duration of diabetes did not have any effect on selenium serum levels. Slightly higher serum selenium in new diabetic patients before the start of therapy was explained by the dehydration state. The patients who were younger than 3 yr had slightly lower selenium serum levels when compared with older age groups. This difference was observed, however, only during the first 3 yr of the study. After that, when the selenium intake increased in general, no age-dependent differences were found anymore. There were no significant differences in serum selenium levels between males and females in either diabetic patients or in controls.     

Serum zinc in patients with cystic fibrosis at diagnosis and after one year of therapy

There is no consensus whether zinc (Zn) supplementation is necessary in cystic fibrosis (CF). For assessment of the Zn status, serum Zn concentration is the only easy available method. It is, however age dependent. We compare the serum Zn levels of CF patients with earlier reported normal values. Serum Zn was determined in all new diagnosed CF patients and a second time 1 yr later. Data concerning fat-soluble vitamin status, cholesterol, albumin, pancreatic insufficiency, and genotype were collected. Thirty-two patients, median age of 1.21 yr, were included. Four were pancreatic sufficient. The median Zn concentration at diagnosis was 10.7 μmol/L (5–21.4), with a significant increase 1 yr later (median: 12.1 μmol/L [7,803–16,1]). An association of serum Zn with vitamin A (p<0.03) and with vitamin E (p<0.02) was observed. Compared to age-matched healthy controls, there is no significant difference in serum Zn concentration either at diagnosis or 1 yr later. Although it was demonstrated that steatorrhoea causes Zn loss, the serum Zn concentration in CF is not significantly different from healthy controls. The relation with vitamin A and E points to the increased losses by steatorrhoea. Therefore, Zn supplementation is advised in persisting steatorrhoea.     

Serum selenium versus lymphocyte subsets and markers of disease progression and inflammatory response in human immunodeficiency virus-1 infection

Serum selenium levels were determined cross-sectionally in 57 HIV-infected patients who were classified according to the Centers for Disease Control (CDC) 1993 classification system. Mean serum selenium levels were lower in CDC stage II (58.7±12.2 μg/L;p<0.01;n=18) and stage III (47.6±11.3 μg/L;p<0.01;n=19) HIV-infected patients, than in healthy subjects (80.6±9.6 μg/L;n=48) and stage I patients (73.6±16.5 μg/L;n=20). Serum selenium levels were positively correlated with CD4 count, CD4/8 ratio, hematocrit, and serum albumin (r=0.42;r=0.39;r=0.48; andr=0.45;p<0.01, respectively) and inversely with serum levels of thymidine kinase (r=−0.49;p<0.01;n=49) and β2-microglobulin (r=−0.46;p<0.001;n=49). In addition, serum selenium levels in 20 randomly selected AIDS-free individuals (CDC I:n=10; CDC II:n=10) were inversely correlated with serum concentrations of interleukin-8 (IL-8) and soluble tumor necrosis factor receptors (sTNFR) types I and II. There was no correlation with serum immuneglobulin A and total serum protein levels. The results show that the progressive deprivation of serum selenium in HIV-infection is associated with loss of CD4⁺-cells and with increased levels of markers of disease progression and inflammatory response.     

Sodium selenite therapy and thyroid-hormone status in cystic fibrosis and congenital hypothyroidism

The effectiveness of a peroral sodium selenite therapy (115 μg Se/m² BSA/d) administered to cystic fibrosis patients (n=32) could after three months be identified in a significant serum selenium increase (0.69→0.96 μmol/L), a significant malondialdehyde decrease (2.72→1.64 μmol/L), as well as in a significant serum vitamin E increase (4.31→5.72 μg/mL) Parallel to that, a serum T₃ increase as well as a highly significant decrease in the serum T₄/T₃-ratio were found, too, which point to improved peripheral T₄→T₃ conversion during selenium medication. Type-I-iodothyronine-5′-deiodinase has recently been identified as a specific selenoenzyme. In the case of congenital hypothyroidism (n=37) application of sodium selenite in the above specified dosage yielded a mean serum selenium increase (0.87→1.12 μmol/L), a not significant T₃ increase (2.57→2.61 nmol/L) as well as a not significant TSH decrease (5.34→4.49 mIU/L) without an expected T₄ decrease. With the serum lipids, however, a lowering of total cholesterol (4.85→4.53 mmol/L) simultaneous with a mean increase in HDL-cholesterol (1.52→1.66 mmol/L) as well as a decrease in LDL-cholesterol (2.93→2.52) could be observed. We view the reduction of the atherogenic serum lipid constellation in the course of selenium medication as an expression of increased thyroid-hormone efficacy.     

Serum extracellular superoxide dismutase activity as an indicator of zinc status in humans

The present study focused on whether serum extracellular superoxide dimutase (EC-SOD) activity can be used as a functional indicator of marginal zinc deficiency in humans. Subjects in this study were 444 healthy adults over 30 yr of age living a normal rural life in Kyunggi province, Korea. The mean dietary zinc intake of subjects obtained from one 24-h recall was 6.41 ± 4.35 mg and the average serum zinc concentration of the subjects was 11.06 ± 2.44 (μmol/L. Subjects were divided into three groups by serum zinc concentrations: adequate (serum zinc >10.7 (μmol/L), low (serum zinc 9.0–10.7 μmol/L), and very low (serum zinc <9.0 μmol/L) groups. A total of 50 subjects were selected from the three groups for analysis of EC-SOD activities. The EC-SOD activity of subjects increased with increasing serum zinc concentrations, and the activities of the three groups were significantly different as indicated by the Kruskal-Wallis test (p = 0.0239). Also, serum EC-SOD activities were significantly correlated with serum zinc concentrations (r = 0.289,p = 0.04). Serum EC-SOD activities, however, were not significantly correlated to the dietary zinc intakes. In conclusion, these results show that EC-SOD activities are decreased in subjects with low serum zinc concentrations and suggest that EC-SOD activity may be a functional indicator of zinc nutritional status in humans.     

Serum Total Selenium Status in Greek Adults and Its Relation to Age. The ATTICA Study Cohort

The trace element selenium is an essential micronutrient for human health and its low levels in serum are implicated in the pathogenesis of several chronic diseases. Therefore, the determination of total selenium in serum may contribute to the assessment of the health and nutritional status of certain populations. The objective of the present work was to determine total selenium in the serum of 506 healthy volunteers that participated in the ATTICA study. Selenium was determined in serum by using the technique of inductively coupled plasma mass spectrometry. The mean serum selenium concentration was determined to be 91.8 ± 33.7 μg/L (N = 506); 87.6% of women and 88.5% of men had serum selenium concentration below 125 μg/L, the cutoff considered to be required for optimal glutathione peroxidase activity. No association was found between serum selenium levels and the gender of the participants while a significant decline of selenium with age (p < 0.0001) was observed. According to our results, no anthropometric, lifestyle, nutritional, or biochemical indices were able to affect the association between serum selenium and age. This result may indicate that other factors such as selenium distribution as well as retention may be affecting the relationship between serum selenium and age.     

Relationship among serum selenium levels,lipid peroxidation,and acute bronchiolitis in infancy

Thirty-four infants with acute bronchiolitis and 25 age-matched healthy controls were enrolled to investigate the possible relationship between serum malondialdehyde (MDA) and selenium (Se) levels and the occurrence and severity of acute bronchiolitis in children. Serum samples were taken for serum Se and MDA measurements, and the clinical score was assessed at admission. Blood was taken again from the children with bronchiolitis at 2 mo after discharge from the hospital. Mean serum MDA levels were significantly higher in patients with acute bronchiolitis than at the postbronchiolitis stage and the controls (4.2±2.5nmol./L, 1.4±0.8 nmol/L, and 0.7±0.2 nmol/L, respectively [p<0.001]). Infants with bronchiolitis had lower mean serum Se levels at the acute stage than after 2 mo (31.7±28.9μg/L versus 68.4±26.4 μg/L, p<0.05, respectively); both of which were significantly lower than the control group measurements (145.0±21.9 μg/L) (p<0.001). There was a negative correlation between serum MDA and Se levels in the patient group (=−0.85, p<0.001). The age of the patient, child's immunization status, parental smoking habit, and family crowding index were not correlated with serum Se, MDA levels, or clinical score at admission. In conclusion, increased MDA levels and impaired Se status demonstrate the presence of possible relationship of these parameters with pathogenesis of acute bronchiolitis, and antioxidant supplementation with Se might be thought to supply a beneficial effect against bronchiolitis.     

Response of Selenium Status Indicators to Supplementation of Healthy North American Men with High-Selenium Yeast

The essential nutrient selenium is required in microgram amounts [recommended dietary allowance (RDA) = 55 μg/day, 699 nmol/day] and has a narrow margin of safety (upper tolerable intake limit = 400 μg/day, 5 μmol/day). We conducted a randomized placebo-controlled study of high-selenium yeast, the form used in most supplements (300 μg/day, 3.8 μmol/day), administered to 42 free-living healthy men for 48 weeks. Dietary intakes of selenium, macronutrients, and micronutrients were not different between groups and did not change during the study. Supplementation more than doubled urinary selenium excretion from 69 to 160 μg/day (876 to 2,032 nmol/day). Urinary excretion was correlated with recent selenium intake estimated from 3-day diet records: urinary selenium excretion = 42 μg/day (533 nmol/day) + 0.132 × dietary selenium intake, p < 0.001. Dietary selenium intake was not significantly correlated with the other indicators of selenium status, presumably because urinary selenium excretion reflected recent intake, and tissue selenium was homeostatically controlled. After 48 weeks of supplementation, plasma selenium was increased 60% from 142 to 228 μg/l (1.8 to 2.9 μmol/l), and erythrocyte selenium was approximately doubled from 261 to 524 μg/l (3.3 to 6.6 μmol/l). Selenium concentrations increased more modestly in hair (56%) and platelets (42%). Platelets were the only blood component in which glutathione peroxidase activity was significantly related to selenium content. Selenium levels decreased rapidly after the end of supplementation, and there were no significant differences in selenium status indicators between groups by week 96. The absorption, distribution, and excretion of selenium from high-Se yeast were similar to selenium in foods.     

Selenium Levels in First-Degree Relatives of Diabetic Patients

The present study was conducted to evaluate the serum selenium levels in first-degree relatives of diabetic patients (FDR) according to controls. Insulin resistance, serum lipid levels, inflammation markers, and blood pressure were also studied in these patients. Serum levels of selenium in FDR were significantly lower than control group (74.65 ± 5.9 vs 88.7 ± 8.7 μg/dl, p < 0.0001). HsCRP, HOMA-IR, insulin, homocysteine levels were significantly higher in FDR according to the control group (1.32 ± 0.9 vs 0.63 ± 0.4 mg/dL, p < 0.0001; 2.07 ± 0.84 vs 1.51 ± 0.69, p < 0.0001; 9.26 ± 3.8 vs 6.8 ± 2.98 μU/MI, p < 0.0001; 15.7 ± 7.4 vs 11.5 ± 5.1 μmol/L, p < 0.0001, respectively). There was significant correlation between selenium levels and hsCRP (r = − 0.450, p < 0.0001). There was also weak significant correlation also between HOMA-IR and selenium levels (r = −0.227, p = 0.003). There was a correlation between systolic blood pressure and BMI (r = 0.365, p < 0.0001). But there was no correlation between selenium levels and blood pressure or other parameters. HsCRP, HOMA-IR, homocysteine levels in individuals with selenium levels < 80 μg/L (n = 78) was significantly higher than hsCRP HOMA-IR, homocysteine levels in individuals with selenium levels ≥ 80 (n = 91; 1.23 ± 0.98 vs 0.81 ± 0.76 mg/dL, p < 0.003; 1.99 ± 0.88 vs 1.64 ± 0.74, p < 0.005; 15.0 ± 7.6 vs 12.9 ± 5.7 μmol/L, p < 0.049, respectively). Selenium deficiency may contribute to cardiovascular disease risk in FDR.     

Serum and hair levels of zinc, selenium, iron, and copper in children with iron-deficiency anemia

In the present study, the serum and hair levels of zinc, selenium, and copper were determined in children with iron-deficiency anemia (IDA). A total of 52 anemic children aged 1–4 yr constituted the study group. Fortysix healthy children acted as controls. The copper and zinc levels were measured with an atomic absorption spectrophometer. Serum and hair selenium was determined by a spectroflourometric method. The serum zinc and selenium concentrations in the IDA group were found to be significantly lower and serum copper significantly higher than those in the controls (p<0.05). Lower iron, zinc, and selenium concentrations (p<0.001) but not copper were found in hair (p>0.05).     

Serum and liver zinc,copper, and iron in chicks infected withEimeria acervulina orEimeria tenella

Two-wk-old broiler chicks were inoculated via crop intubation withEimeria acervulina at two doses: 10⁵ or 10⁶ sporulated oocysts/bird or withEimeria tenella at a dose of 10⁵ sporulated oocysts/bird. Serum and liver samples were collected on days 3 and 6 post-inoculation (PI). There were no significant changes in serum or liver zinc, copper, and iron concentrations in any of the infected groups by 3 d PI. However, on d 6, PI serum protein was significantly reduced in all of the infected groups compared to their pair-fed controls. The chicks infected withE. tennella had significantly reduced serum zinc (1.20 vs 1.77 μg/mL) and iron (0.44 vs 1.28 μg/mL) concentrations and significantly elevated serum copper (0.28 vs 0.17 μg/mL) and ceruloplasmin levels (20.33 vs 11.11 μg/mL) compared to their pair-fed counterparts. Those chicks infected withE. acervulina (10⁶ oocysts/bird) exhibited significantly reduced serum iron concentration by 6 days PI (0.90 vs 1.14 μg/mL). Liver zinc was significantly increased in the chicks infected withE. tenella (349 vs 113 μg/g dry liver wt), as was copper (24 vs 19 μg/g), whereas liver iron concentration was significantly reduced (172 vs 243 μg/g) compared to pair-fed controls. At both dose levels, the chicks infected withE. acervulina exhibited a significant reduction in liver iron by 6 d PI. Hepatic cytosol metals generally reflected whole tissue levels. Metallothionein (MT)-bound zinc was significantly elevated in the chicks infected withE. tenella. Iron bound to a high molecular weight, heat-stable protein fraction (presumably cytoplasmic ferritin) was significantly reduced in chicks infected withE. acervulina, as well as those infected withE. tenella. Collectively, the changes in serum zinc, copper, and iron concentrations, as well as the changes in hepatic zinc and MT-zinc concentrations in the chicks infected withE. tenella were similar to changes evoked during an acute phase response to infection. It is possible that a secondary bacterial infection or inflammation stemming from erosion of the lining of the cecum may play a role in the response of trace element metabolism to theE. tenella infection. Mentions of a trademarkr, proprietary product or specific equipment does not consitute a guarantee or warranty by the US Department of Agriculture and does not imply its approval to the exclusion of other products.     

Effects of trace elements on the telomere lengths of hepatocytes L-02 and hepatoma cells SMMC-7721

The effects of selenium, zinc, iron, chromium, and lead on telomere lengths of human cells have not been investigated. This article adopted flow cytometry and fluorescence in situ hybridization to investigate the impact of different elements on cellular apoptosis and telomere lengths of human hepatocytes L-02 and hepatoma cells SMMC-7721. Results showed that these trace elements under the following dosages did not have remarkable effect on cellular apoptosis. However, sodium selenite at doses of 0.5 and 2.5 μmol/L significantly extended the telomere length of hepatocytes L-02; 0.5 μmol/L lead acetate remarkably shortened the telomere length of L-02 cells; 80 μmol/L zinc sulfate, 20 μmol/L ferric chloride, and 200 μmol/L chromic chloride only had slight impact on the telomere length, respectively. Regarding hepatoma cells SMMC-7721, sodium seleite at 0.5 and 2.5 μmol/L had little impact on the telomere length; 80 μmol/L zinc sulfate significantly accelerated the loss of telomere length, whereas 20 μmol/L ferric chloride, 200 μmol/L chromic chloride, and 0.5 μmol/L lead acetate remarkably extended the telomere lengths, respectively. The results revealed differential effects of each trace element on the life-span of human hepatocytes and hepatoma cell lines, which suggested further research on somatic hepatocytes and hepatoma in vivo.     

Effects of Vitamin E and Selenium on Serum Trace and Major Elements in Horses

The combined effects of vitamin E and selenium were studied in native Anatolian horses subject to strenuous exercise. The concentrations of copper, zinc, iron, calcium, potassium, and magnesium were determined in serum by atomic absorption spectrometry in two study groups (n = 25 each), one of which served as untreated controls. After exercising the horses by running 1,500 m in about 7 min, only the copper level and the copper/zinc ratio significantly increased (p < 0.05), but the concentrations of calcium, potassium, iron, and magnesium remained unchanged. In horses treated with vitamin E and selenium, the calcium and potassium levels decreased to levels lower than those of untreated controls before and after exercise. The iron levels were not changed by exercise or treatment alone but increased when the horses had been supplemented and exercised. The copper level and the copper/zinc ration increased as a result of exercise in both treated and untreated horses. These changes suggest that supplementation with vitamin E and selenium had an important effect on the serum concentrations of calcium, potassium, copper, iron, and the copper/zinc ratio.     

Consistent relationship between selenium and apolipoprotein A-II concentrations in the sera of fasting middle-aged male abstainers and regular consumers of alcohol

Several studies have suggested that selenium serum levels may be associated with serum lipids and apolipoproteins. In the present study, 99 clerical workers aged 40–49 yr were selected based on their drinking and smoking habits. The serum concentration of selenium was not affected by these lifestyle factors. The regular drinkers had raised serum high-density lipoprotein cholesterol, apo A-I, and apo A-II concentrations. Correlation analysis showed that serum selenium was positively and consistently associated with apo A-II regardless of alcohol consumption. Factor analysis revealed that serum selenium had no association with factors that represented each lipoprotein fraction (LDL, HDL, and VLDL). The present study indicates that serum selenium is positively correlated only with apo A-II levels.     

The response of trout and zebrafish embryos to low and high boron concentrations is U-shaped

Fish in the embryo-larval stage of development have been shown to be sensitive to boron (B) at both ends of the dose-response curve (1,2). The present study evaluated the health effects of low and high B concentrations on rainbow trout (Oncorhynchus mykiss), a cold water species, and zebrafish (Danio rerio), a warm water species. Rainbow trout embryos were incubated from day 1 until 2 wk posthatch in Type 1 ASTM ultrapure-grade water (12.5°C) supplemented with only B (0-500 μM) as boric acid, or together with CaCO₃ (0–2 mM) to increase water hardness. Embryonic growth was stimulated by B in a dose-dependent manner at all Ca concentrations (p < 0.001). Chronic exposures below 9 μmol B/L impaired embryonic growth and above 10 mmol B/L caused death (p < 0.001). Thus, the safe range of exposure for the rainbow trout was between the adverse effect concentrations of 9 μmol B/L and 10 mmol B/L. Zebrafish were maintained for 6 mo in ultrapure water containing <0.2 μmol B/L to determine the effect of low-level exposure. High-level exposure was assessed by exposing zygotes, derived from parents maintained at 46 μmol B/L, to graded concentrations of boric acid up to a concentration of 75 mmol B/L from fertilization until they were free feeding (96 h). Fertilization occurred, but zygotes failed to survive when water contained <0.2 umol B/L (p < 0.001). Death occurred at and above 9.2 mmol B/L. Thus, the safe range of B exposure for zebrafish was between the adverse effect concentrations of 0.2 μmol B/L and 9.2 mmol B/L. The dose-response for both species was thus U-shaped. Part of this work was previously published in abstract form and presented at Experimental Biology 97, April 6–9, New Orleans, LA (Eckhert, C. [1997] Embryonic trout growth and boron exposure,FASEB J. 11, A406 [abstract]).