Serum iron, copper, zinc, ferritin, and ceruloplasmin after intense heat exposure

Influence of a high-temperature programme on serum, urinary and sweat levels of selenium and zinc

INTRODUCTION

The effect of hyperthermia on the antioxidant system in the human organism is well known.

AIM

The objective of this study was to observe the effects of heat on the concentration of Se and Zn, elements related to antioxidant systems.

METHODS

Twenty-nine subjects voluntarily participated in this study. They were divided into a control group (CG; n = 14) and an experimental group (EG; n = 15). All of them underwent two incremental tests until exhaustion in normothermia (22 °C, 20-40%RH) and hyperthermia (42 °C, 20-40%RH). EG experienced nine sessions of repeated heat exposure at high temperatures (100 °C, 20%RH) for three weeks (HEHT). After the intervention, the initial measurements were repeated. Urine and blood samples were collected before and after each test. Additionally, sweat samples were collected after tests in hyperthermia.

RESULTS

There were no significant changes in serum. An increase in the elimination of Zn and Se in EG was observed in urine after HEHT (p < .05). The elimination of Zn by sweating decreased after HEHT in EG (p < .05).

CONCLUSIONS

Exposure to heat at high temperatures increases the urinary excretion of Se and Zn.

Zinc and the prooxidant heart failure phenotype

Neurohormonal activation with attendant aldosteronism contributes to the clinical appearance of congestive heart failure (CHF). Aldosteronism is intrinsically coupled to Zn and Ca dyshomeostasis, in which consequent hypozincemia compromises Zn homeostasis and Zn-based antioxidant defenses that contribute to the CHF prooxidant phenotype. Ionized hypocalcemia leads to secondary hyperparathyroidism with parathyroid hormone-mediated Ca overloading of diverse cells, including cardiomyocytes. When mitochondrial Ca overload exceeds a threshold, myocyte necrosis follows. The reciprocal regulation involving cytosolic free [Zn]i as antioxidant and [Ca]i as prooxidant can be uncoupled in favor of Zn-based antioxidant defenses. Increased [Zn]i acts as a multifaceted antioxidant by: (1) inhibiting Ca entry through L-type channels and hence cardioprotectant from the Ca-driven mitochondriocentric signal-transducer effector pathway to nonischemic necrosis, (2) serving as catalytic regulator of Cu/Zn-superoxide dismutase, and (3) activating its cytosolic sensor, metal-responsive transcription factor that regulates the expression of relevant antioxidant defense genes. Albeit present in subnanomolar range, increased cytosolic free [Zn]i enhances antioxidant capacity that confers cardioprotection. It can be achieved exogenously by ZnSO4 supplementation or endogenously using a β3-receptor agonist (eg, nebivolol) that enhances NO generation to release inactive cytosolic Zn bound to metallothionein. By recognizing the pathophysiologic relevance of Zn dyshomeostasis in the prooxidant CHF phenotype and by exploiting the pharmacophysiologic potential of [Zn]i as antioxidant, vulnerable cardiomyocytes under assault from neurohormonal activation can be protected and the myocardium spared from adverse structural remodeling.

Zinc dyshomeostasis in rats with aldosteronism. Response to spironolactone

Zinc is a structural constituent of many proteins, including Cu/Zn superoxide dismutase (SOD), an endogenous antioxidant enzyme. Hypozincemia has been found in patients hospitalized with congestive heart failure, where neurohormonal activation, including the renin-angiotensin-aldosterone system (RAAS), is expected and oxidative stress is present. This study was undertaken to elucidate potential pathophysiological mechanisms involved in Zn dyshomeostasis in aldosteronism. In rats receiving aldosterone/salt treatment (ALDOST) alone for 1 and 4 wk or in combination with spironolactone (Spiro), an ALDO receptor antagonist, we monitored 24-h urinary and fecal Zn excretion and tissue Zn levels in heart, liver, and skeletal muscle, together with tissue metallothionein (MT)-I, a Zn(2+)-binding protein, and Cu/Zn-SOD activities in plasma and tissues. When compared with unoperated, untreated, age-/sex-matched controls, urinary and, in particular, fecal Zn losses were markedly increased (P < 0.05) at days 7 and 28 of ALDOST, leading to hypozincemia and a fall (P < 0.05) in plasma Cu/Zn-SOD activity. Microscopic scars and perivascular fibrosis of intramural coronary arteries first appeared in the right and left ventricles at week 4 of ALDOST and were accompanied by increased (P < 0.05) tissue Zn, MT-I, and Cu/Zn-SOD activity, which were not found in uninjured liver or skeletal muscle. Spiro cotreatment prevented cardiac injury and Zn redistribution to the heart. Thus increased urinary and fecal Zn losses, together with their preferential translocation to sites of cardiac injury, where MT-I overexpression and increased Cu/Zn-SOD activity appeared, contribute to Zn dyshomeostasis in rats with aldosteronism, which were each prevented by Spiro. These findings may shed light on Zn dyshomeostasis found in patients with decompensated heart failure.

Effect of environmental temperature on tissue lead accumulation in mice repeatedly treated with lead acetate

The effect of environmental temperature on lead accumulation in tissues of mice repeatedly treated with lead acetate (2 mg/kg per day and 5 mg/kg per day) for 3 or 6 weeks was studied. In blood, kidney and liver, the amount of lead accumulated after 3 weeks of treatment was markedly higher in animals exposed to 22 degrees C than those maintained at 35 degrees C. Conversely, when the treatment was extended to 6 weeks, lead concentrations in the liver and kidney were equal or higher respectively, in the mice exposed to 35 degrees C. In the brain, lead concentration was lower than that found in kidney and liver and it was independent of dose and ambient temperature of lead being higher at 35 degrees C than at 22 degrees C. These results demonstrate that environmental temperature influences the amount of lead accumulated in some rodent tissues, and that the duration of the treatment modifies the effect produced by temperature, suggesting that the changes elicited during the period of acclimation to the hot environment could be responsible for these findings.

Dietary intake and thiamin, iron, and zinc status in elite Nordic skiers during different training periods

This study evaluated how different training periods affect dietary intake and biochemical indices of thiamin, iron, and zinc status in elite Nordic skiers. Subjects were 17 skiers and 39 controls, ages 18-38 yrs. Dietary data were collected by 7-day food records at 3-month intervals. Coefficient of variation (CV) was used to indicate magnitude of seasonal changes. Energy intake for the year (28 food record days) was 3,802 kcal/day (CV 19.1%) in male skiers, 2,754 kcal/day (CV 3.7%) in male controls, 2,812 kcal/day (CV 9.1%) in female skiers, and 2,013 kcal/day (CV 5.9%) in female controls. CVs for thiamin, riboflavin, vitamin C, calcium, magnesium, iron, and zinc intake were 14.1-23.9% (male skiers), 2.9-15.0% (male controls), 4.8-24.5% (female skiers), and 4.3-11.5% (female controls). Seasonal changes in energy, carbohydrate, and micronutrient intakes reflected energy expenditure in male endurance athletes particularly. Erythrocyte transketolase activation coefficients and serum ferritin and zinc concentrations did not differ between skiers and controls. Seasonal variations in these biochemical indices of nutritional status were of the same magnitude in skiers and controls, despite large changes in skiers' physical activity.

Iron status in Winter Olympic sports

Iron status was surveyed amongst 92 Winter Olympic sport athletes from Nordic and Alpine skiing, figure and speed skating and ice hockey. Haemoglobin and serum ferritin values were obtained by physicians as part of a monitoring programme, since iron deficiency would have an adverse effect on maximal performance. Four (7%) of 56 men were anaemic (Hb less than 14.0 g dl-1) and three (8%) of 36 women had haemoglobin values less than 12.0 g dl-1. Nine men (16%) and 14 women (39%) had prelatent iron deficiency (serum ferritin less than 30 ng ml-1). Ice hockey had the lowest while Nordic skiing had the highest incidence of sub-optimal iron status. A total of 50% of Nordic women skiers had prelatent iron deficiency and 7% were anaemic. An equal percentage of women speed skaters were low in serum ferritin as well. Only one of 20 male ice hockey players was low in serum ferritin. These results suggest there would be value in instituting screening procedures for iron status in Winter Olympic Sports.

Some cardiovascular and metabolic effects of repeated sauna bathing

Ten healthy male volunteers were exposed to the dry heat of a Finnish sauna (+80 degrees C) for 1 h twice a day for a period of 7 days. After each exposure rectal temperature rose by 0.8-1.1 degrees C and body weight dropped by 0.7-0.9 kg. The systolic blood pressure recorded 3-5 min after the sauna did not change during the experiments but the diastolic blood pressure decreased by 7-37 mmHg (P less than 0.05). The pulse rate rose from 75-80 to 106-116 beats min-1 (P less than 0.05) after the sauna. The increased responses of pulse and temperature adapted to heat exposures so that they were significantly lower after the 3rd day (rectal temperature) or after 6th day (pulse). Metabolic rate increased by 25-33% (P less than 0.01) after the first day. Serum total proteins, Hb and Htc were significantly increased on the 1st and 3rd days but not later, although the dehydration in response to sauna was unchanged as judged from the weight losses. Serum K, Na and Fe were significantly decreased on the 3rd and 7th day indicating that special attention should be given to the electrolyte balance in long-lasting intense heat exposure. No ECG changes were found in recordings taken on the 7th day.