Effects of ambient cadmium with calcium on mRNA expressions of calcium uptake related transporters in zebrafish (Danio rerio) larvae

Abstract

The mRNA expression levels of Ca²⁺ transporter genes including the epithelial calcium channel (ECaC), sodium/calcium exchanger 1b (NCX1b), and plasma membrane calcium ATPase 2 (PMCA2) were measured in zebrafish larvae after exposure to 0.08 μM Cd²⁺ in either water mixed with 0.2 mM Ca²⁺ (lCa) or 2 mM Ca²⁺ (hCa). The ECaC and NCX1b expression decreased at the 48 and 72 h mark, respectively; however, PMCA2 transcripts decreased at 96 h after exposure to Cd²⁺ in lCa environment. On the other hand, the ECaC transcripts were not affected; however, the PMCA2 transcripts were increased at 72 h, while the NCX1b transcripts significantly decreased at 48 and 96 h after exposure to Cd²⁺ in a hCa environment. The Ca²⁺ contents of larvae significantly decreased after Cd²⁺ exposure in a lCa environment; however, the Ca²⁺ contents were evidently higher after exposure to Cd²⁺ in a hCa environment, except for 48th h mark. In addition, ECaC morphants showed lower Ca²⁺ contents of whole-body, and there were higher levels of mortality after exposure to the same condition compared to the wild-type groups. In contrast, injection of ECaC cRNA resulted in an increase in Ca²⁺ content and the rate of Ca²⁺ influx in zebrafish embryos. Summary, the results showed that the Ca²⁺ transporters of zebrafish larvae were impacted after exposures of 0.08 μM Cd. However, in the exposure condition, the ECaC and PMCA2 transcripts could be restored to control levels after the fish were treated in an environment with hCa.

Using physiology and behaviour to understand the responses of fish early life stages to toxicants

“…Metabolic costs of toxicant exposure may also be acquired through ionoregulatory disruption (McGeer et al , 2000; Wood, 2001), which may have knock‐on effects for behaviour (Sloman et al , 2002). Toxicant‐induced ionoregulatory disruption is seen in early life stages; cadmium competitively inhibits calcium uptake in tilapia Oreochromis mossambicus (Peters 1852) larvae (Chang et al , 1997), down‐regulates calcium transporters in D. rerio larvae (Liu et al , 2012) and directly alters the morphology and density of chloride cells within O. mossambicus embryos (Lee et al , 1996). Low concentrations of cadmium (50 µg l −1 ) stimulated chloride cell activity, whereas higher concentrations (200 µg l −1 ) prevented the development of microvilli in the apical crypts suggesting a reduced ionoregulatory capacity (Lee et al , 1996).…”

Zinc and Calcium Supplementation to Combat Cadmium Induced Bioaccumulation in Fresh Water Teleost Oreochromis Mossambicus (Tilapia)

“…Chelating agents are capable of linking together metal ions to form complex structures which can be easily excreted from the body. Cd can compete and interact metabolically with essential nutrients such as selenium (Se), Ca, Zn, copper (Cu) and iron (Fe) in the body [25][26][27]. Zn is the most abundant trace intracellular element required for a number of cellular processes, including cell proliferation, reproduction, immune function and defense against free radicals [28].…”

“…Cd accumulation was reduced with the increase of waterborne and dietary Ca [31][32][33]. Higher water Ca levels reduce the amount of Cd binding to girls [27] and reduce bronchial Cd uptake rates resulting in lower accumulation in the kidney, liver and other tissues of fish. Hence the present study was carried out to know whether the supplementation of Zn and Ca either individually or in combination would reduce the Cd bioaccumulation in the selected tissues of Cd-exposed Oreochromis mossambicus.…”

Anti-oxidative functions of mt2 and smtB mRNA expression in the gills and brain of zebrafish (Danio rerio) upon cadmium exposure

“…In addition, our previous study has reported that the zebrafish b-actin gene appeared suitable as a reference gene on Cd 2? exposure study (Liu et al 2012). These antioxidant enzymes, including mRNA levels of sod, cat, and gpx1a, respectively, increased 2.2-, 1.6-, and 3.1-fold after 1 h of Cd 2?…”