Environ Sci Pollut Res DOI 10.1007/s11356-015-4249-5
RESEARCH ARTICLE
Effects of low-dose cadmium exposure during gestation and lactation on development and reproduction in rats Xue Luo & Lianbing Li & Mingfu Ma & Renyan Li
Received: 13 November 2014 / Accepted: 17 February 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Cadmium (Cd) is an important toxic chemical due to its increasing levels in the environment and its resulting accumulation in humans and animals. The present study was performed to evaluate the long-term effects of low doses of Cd administered in offspring by oral route to rats during pregnancy and lactation. There were no adverse effects on the physical and sexual development in the pups, except to delay the development of offspring. The relative weights of livers and kidneys in the adult female offspring were significantly decreased after exposure to 10 ppm Cd. These results indicated that there were adverse effects on growth and development from exposure to 5 or 10 ppm Cd in utero and during lactation. The results also showed differential gender sensitivity effects on the organ weights. Keywords Cadmium . Utero and lactation exposure . Low doses . Development . Reproduction Abbreviations Cd Cadmium GD Gestational day PND Postnatal day AGD Anogenital distance SD Sprague Dawley FSH Follicle-stimulating hormone LH Luteotropic hormone Responsible editor: Philippe Garrigues X. Luo Institute of Tropical Medicine, Third Military Medical University, Chongqing 400038, People’s Republic of China L. Li : M. Ma : R. Li (*) Key Laboratory of Birth Defects and Reproductive Health, Chongqing Institute of Population and Family Planning, Chongqing 400020, People’s Republic of China e-mail: [email protected]
ELISA SE Zn Cu
Enzyme-linked immunospecific assay Standard error Zinc Copper
Introduction Cadmium (Cd) is a heavy metal that is a serious environmental hazard for human health (Godt et al. 2006; Jarup 2002; Jarup and Akesson 2009). The most significant sources of occupational Cd exposure usually occur during mining or manufacturing of batteries and pigments that utilize Cd (Klaassen et al. 2009). Smelting and refining of metals and municipal waste incineration release Cd into the environment as cadmium oxide, cadmium chloride, or cadmium sulfide, which contaminate the water, air, soil, and airborne dust (Thevenod and Lee 2013). In addition, cigarette smoking is another important contributor to the Cd body burden (Klaassen et al. 2009). The Cd levels in the air, food, and drinking water are usually less than 0.04 μg/m 3 , 1 μg Cd/day, or 1 μg/L, respectively (Anetor 2012), and the concentration of Cd in the food obtained from the markets is 0.01–0.09 mg/kg, which is lower than the provisional tolerable daily intake proposed by the Joint FAO/WHO Expert Committee on Food Additives (Akinyele and Shokunbi 2015). However, an additional 1–3 μg of Cd can be absorbed by smoking one pack of cigarettes per day, and consequently, heavy smokers have more than double the Cd body burden (Waalkes 2003). Cd has a long biological half-life of 20–40 years in humans, and it accumulates in the body over a considerable period of time (Thevenod and Lee 2013). Pregnant and lactating female animals were reported to absorb and retain substantially more dietary Cd than their
Environ Sci Pollut Res Fig. 1 The study design and the measured gross physiological parameters (i.e., body mass, sex ratio, and reproductive parameters) of the maternal rats (F0) and pups (F1) are shown
non-pregnant counterparts (Bhattacharyya et al. 1982), and Cd toxicity could be transferred to the fetus (Whelton et al. 1993). The effects of Cd toxicity on fetal development have been studied for several decades. Some epidemiological studies have shown an association between gestational exposure to Cd and fetal development (Frery et al. 1993; Salpietro et al. 2002; Shirai et al. 2010). Conversely, other studies did not find any relationship between Cd exposure and fetal development (Galicia-Garcia et al. 1997; Lin et al. 2011; Loiacono et al. 1992; Nishijo et al. 2004b; Odland et al. 1999, 2004). The inconsistent results of epidemiological studies may be due to exposure to different doses of Cd. Therefore, it is necessary to clarify the toxicity effects of Cd on the offspring of animals in the laboratory. In animal studies, exposure to Cd (0.04–4 mg/kg body weight (BW) or 60–180 ppm) was linked to fetal growth retardation (Baranski 1987; Hastings et al. 1978) and congenital malformations in the offspring (Chernoff 1973; Gale and Ferm 1973). However, low doses of Cd exposure to animals showed no adverse effects on the offspring. The pregnant mice received 1 or 10 ppm Cd as cadmium chloride in the drinking water, from gestational day (GD) 0 to postnatal day (PND) 10, and the results showed no effects on the reproductive performance of the pregnant mice, and the sexual maturation and function of female offspring (Ishitobi and Watanabe 2005). Another study showed that there were adverse effects on the reproductive system in the offspring when the pregnant rats received 10 mg Cd/L in drinking water from GD 0 to PND 5 (Corpas and Antonio 1998). However, the effects of lowdose Cd exposure from GD 0 to weaning (PND 21), and the long-lasting effects on the offspring are still poorly understood. The purpose of the present study was therefore to determine whether gestational and lactating period exposure to Table 1
Materials and methods Animals Male and female Sprague Dawley (SD) rats, at 3 months of age, were provided by the Daping Hospital Third Military Medical University Experimental Animal Center (Chongqing, China). This study was approved by the Third Military Medical University Institutional Animal Care and Use Committee, and the experiments were conducted under strict principles of Good Laboratory Practice to ensure good quality in vivo toxicology studies. Rats were maintained in air-conditioned rooms at a temperature of 20–22 °C and 50–70 % humidity with controlled lighting (12-h light and 12-h darkness). Food and water were given ad libitum. The animals were acclimated to the laboratory for 1 week prior to the start of the experiments. Mating procedures Each female was mated with a single male until copulation occurred or the mating period had elapsed. During the mating period, daily vaginal smears were examined for the presence of sperm. The presence of sperm in the vaginal smear was considered evidence for successful mating. The day of successful mating was designated as day 0 of pregnancy. The maternal body weight was measured weekly after pregnancy.
Cadmium ingestion of mothers
Cd2+ consumption/day (mg)a Cd2+ consumption mg/kg bw a
0, 1, 5, or 10 ppm Cd in the drinking water had adverse effects on the birth weight, growth and development, and reproductive parameters of the offspring.
Control
1 ppm
5 ppm
10 ppm
0 0
0.03±0.001 0.089±0.001
0.15±0.01 0.439±0.061
0.3±0.02 0.955±0.086
Results calculated in relation to daily consumed water
bw body weight
Environ Sci Pollut Res
Cadmium exposure The pregnant rats were randomly divided into four groups (n= 10 for each group). The pregnant animals in the treated groups received 1 ppm (1 mg/L), 5 ppm (5 mg/L), or 10 ppm (10 mg/L) Cd as cadmium chloride in the drinking water from GD 0 to lactating day 21. The control group received only distilled water.
From PND 21, the pups in all of the groups were given distilled water to drink. The individual water consumption was recorded weekly. The detected parameters and time points are shown in Fig. 1. Litter data Once insemination was confirmed, the female rats were checked at least three times daily on days 20 to 23 of pregnancy to determine the time of delivery. The pregnant rats were allowed to deliver spontaneously and nurse their pups until PND 21 (the day of weaning). The day on which parturition was completed, at 9:00 a.m., was designated as PND 0. Total litter size and live pups were counted and individually weighed, and body size was measured weekly from postnatal 0 to 12 weeks.
Fig. 2 Effect of maternal cadmium (Cd) exposure of 0, 1, 5, or 10 ppm during pregnancy and lactation (from gestational day 0 to lactation day 21) on a maternal body weight (g), b gestation length (days), c number of pups delivered by each pregnant rats, and d sex ratio (males to females) of the offspring. Data represent mean±SE, and n=10 pregnant females in each group
Fig. 3 Body weights of pups from dams exposed to Cd in drinking water at doses of 0, 1, 5, or 10 ppm, which were detected once a week from postnatal 0 to 12 weeks. a The body weight in the whole offspring population from postnatal 0 to 12 weeks. b The body weight in the male offspring from postnatal 3 to 12 weeks. c The body weight in the female offspring from postnatal 3 to 12 weeks. The pups were weighed individually, and the values are expressed as mean±SE; n=10. *Exposure to 10 ppm Cd significantly different from the control; #exposure to 5 ppm Cd significantly different from the control, P
RESEARCH ARTICLE
Effects of low-dose cadmium exposure during gestation and lactation on development and reproduction in rats Xue Luo & Lianbing Li & Mingfu Ma & Renyan Li
Received: 13 November 2014 / Accepted: 17 February 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Cadmium (Cd) is an important toxic chemical due to its increasing levels in the environment and its resulting accumulation in humans and animals. The present study was performed to evaluate the long-term effects of low doses of Cd administered in offspring by oral route to rats during pregnancy and lactation. There were no adverse effects on the physical and sexual development in the pups, except to delay the development of offspring. The relative weights of livers and kidneys in the adult female offspring were significantly decreased after exposure to 10 ppm Cd. These results indicated that there were adverse effects on growth and development from exposure to 5 or 10 ppm Cd in utero and during lactation. The results also showed differential gender sensitivity effects on the organ weights. Keywords Cadmium . Utero and lactation exposure . Low doses . Development . Reproduction Abbreviations Cd Cadmium GD Gestational day PND Postnatal day AGD Anogenital distance SD Sprague Dawley FSH Follicle-stimulating hormone LH Luteotropic hormone Responsible editor: Philippe Garrigues X. Luo Institute of Tropical Medicine, Third Military Medical University, Chongqing 400038, People’s Republic of China L. Li : M. Ma : R. Li (*) Key Laboratory of Birth Defects and Reproductive Health, Chongqing Institute of Population and Family Planning, Chongqing 400020, People’s Republic of China e-mail: [email protected]
ELISA SE Zn Cu
Enzyme-linked immunospecific assay Standard error Zinc Copper
Introduction Cadmium (Cd) is a heavy metal that is a serious environmental hazard for human health (Godt et al. 2006; Jarup 2002; Jarup and Akesson 2009). The most significant sources of occupational Cd exposure usually occur during mining or manufacturing of batteries and pigments that utilize Cd (Klaassen et al. 2009). Smelting and refining of metals and municipal waste incineration release Cd into the environment as cadmium oxide, cadmium chloride, or cadmium sulfide, which contaminate the water, air, soil, and airborne dust (Thevenod and Lee 2013). In addition, cigarette smoking is another important contributor to the Cd body burden (Klaassen et al. 2009). The Cd levels in the air, food, and drinking water are usually less than 0.04 μg/m 3 , 1 μg Cd/day, or 1 μg/L, respectively (Anetor 2012), and the concentration of Cd in the food obtained from the markets is 0.01–0.09 mg/kg, which is lower than the provisional tolerable daily intake proposed by the Joint FAO/WHO Expert Committee on Food Additives (Akinyele and Shokunbi 2015). However, an additional 1–3 μg of Cd can be absorbed by smoking one pack of cigarettes per day, and consequently, heavy smokers have more than double the Cd body burden (Waalkes 2003). Cd has a long biological half-life of 20–40 years in humans, and it accumulates in the body over a considerable period of time (Thevenod and Lee 2013). Pregnant and lactating female animals were reported to absorb and retain substantially more dietary Cd than their
Environ Sci Pollut Res Fig. 1 The study design and the measured gross physiological parameters (i.e., body mass, sex ratio, and reproductive parameters) of the maternal rats (F0) and pups (F1) are shown
non-pregnant counterparts (Bhattacharyya et al. 1982), and Cd toxicity could be transferred to the fetus (Whelton et al. 1993). The effects of Cd toxicity on fetal development have been studied for several decades. Some epidemiological studies have shown an association between gestational exposure to Cd and fetal development (Frery et al. 1993; Salpietro et al. 2002; Shirai et al. 2010). Conversely, other studies did not find any relationship between Cd exposure and fetal development (Galicia-Garcia et al. 1997; Lin et al. 2011; Loiacono et al. 1992; Nishijo et al. 2004b; Odland et al. 1999, 2004). The inconsistent results of epidemiological studies may be due to exposure to different doses of Cd. Therefore, it is necessary to clarify the toxicity effects of Cd on the offspring of animals in the laboratory. In animal studies, exposure to Cd (0.04–4 mg/kg body weight (BW) or 60–180 ppm) was linked to fetal growth retardation (Baranski 1987; Hastings et al. 1978) and congenital malformations in the offspring (Chernoff 1973; Gale and Ferm 1973). However, low doses of Cd exposure to animals showed no adverse effects on the offspring. The pregnant mice received 1 or 10 ppm Cd as cadmium chloride in the drinking water, from gestational day (GD) 0 to postnatal day (PND) 10, and the results showed no effects on the reproductive performance of the pregnant mice, and the sexual maturation and function of female offspring (Ishitobi and Watanabe 2005). Another study showed that there were adverse effects on the reproductive system in the offspring when the pregnant rats received 10 mg Cd/L in drinking water from GD 0 to PND 5 (Corpas and Antonio 1998). However, the effects of lowdose Cd exposure from GD 0 to weaning (PND 21), and the long-lasting effects on the offspring are still poorly understood. The purpose of the present study was therefore to determine whether gestational and lactating period exposure to Table 1
Materials and methods Animals Male and female Sprague Dawley (SD) rats, at 3 months of age, were provided by the Daping Hospital Third Military Medical University Experimental Animal Center (Chongqing, China). This study was approved by the Third Military Medical University Institutional Animal Care and Use Committee, and the experiments were conducted under strict principles of Good Laboratory Practice to ensure good quality in vivo toxicology studies. Rats were maintained in air-conditioned rooms at a temperature of 20–22 °C and 50–70 % humidity with controlled lighting (12-h light and 12-h darkness). Food and water were given ad libitum. The animals were acclimated to the laboratory for 1 week prior to the start of the experiments. Mating procedures Each female was mated with a single male until copulation occurred or the mating period had elapsed. During the mating period, daily vaginal smears were examined for the presence of sperm. The presence of sperm in the vaginal smear was considered evidence for successful mating. The day of successful mating was designated as day 0 of pregnancy. The maternal body weight was measured weekly after pregnancy.
Cadmium ingestion of mothers
Cd2+ consumption/day (mg)a Cd2+ consumption mg/kg bw a
0, 1, 5, or 10 ppm Cd in the drinking water had adverse effects on the birth weight, growth and development, and reproductive parameters of the offspring.
Control
1 ppm
5 ppm
10 ppm
0 0
0.03±0.001 0.089±0.001
0.15±0.01 0.439±0.061
0.3±0.02 0.955±0.086
Results calculated in relation to daily consumed water
bw body weight
Environ Sci Pollut Res
Cadmium exposure The pregnant rats were randomly divided into four groups (n= 10 for each group). The pregnant animals in the treated groups received 1 ppm (1 mg/L), 5 ppm (5 mg/L), or 10 ppm (10 mg/L) Cd as cadmium chloride in the drinking water from GD 0 to lactating day 21. The control group received only distilled water.
From PND 21, the pups in all of the groups were given distilled water to drink. The individual water consumption was recorded weekly. The detected parameters and time points are shown in Fig. 1. Litter data Once insemination was confirmed, the female rats were checked at least three times daily on days 20 to 23 of pregnancy to determine the time of delivery. The pregnant rats were allowed to deliver spontaneously and nurse their pups until PND 21 (the day of weaning). The day on which parturition was completed, at 9:00 a.m., was designated as PND 0. Total litter size and live pups were counted and individually weighed, and body size was measured weekly from postnatal 0 to 12 weeks.
Fig. 2 Effect of maternal cadmium (Cd) exposure of 0, 1, 5, or 10 ppm during pregnancy and lactation (from gestational day 0 to lactation day 21) on a maternal body weight (g), b gestation length (days), c number of pups delivered by each pregnant rats, and d sex ratio (males to females) of the offspring. Data represent mean±SE, and n=10 pregnant females in each group
Fig. 3 Body weights of pups from dams exposed to Cd in drinking water at doses of 0, 1, 5, or 10 ppm, which were detected once a week from postnatal 0 to 12 weeks. a The body weight in the whole offspring population from postnatal 0 to 12 weeks. b The body weight in the male offspring from postnatal 3 to 12 weeks. c The body weight in the female offspring from postnatal 3 to 12 weeks. The pups were weighed individually, and the values are expressed as mean±SE; n=10. *Exposure to 10 ppm Cd significantly different from the control; #exposure to 5 ppm Cd significantly different from the control, P
