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

The mRNA expression levels of Ca(2+) 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 Cd(2+) in either water mixed with 0.2 mM Ca(2+) (lCa) or 2 mM Ca(2+) (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 Cd(2+) 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 Cd(2+) in a hCa environment. The Ca(2+) contents of larvae significantly decreased after Cd(2+) exposure in a lCa environment; however, the Ca(2+) contents were evidently higher after exposure to Cd(2+) in a hCa environment, except for 48th h mark. In addition, ECaC morphants showed lower Ca(2+) 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 Ca(2+) content and the rate of Ca(2+) influx in zebrafish embryos. Summary, the results showed that the Ca(2+) 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.