The influence of Ca concentration on voltage-dependent L-type calcium channels' expression in the marbled eel (Anguilla marmorata).

The catadromous species, eels, invariably exposed to variable Ca concentrations circumstance i.e., lagoon or ocean. They need to maintain Ca homeostasis by exchanging Ca under different culture conditions. To understand the effects of environmental Ca to fish, three types of genes coding for voltage-dependent L-type calcium channels (cacnb1, 2, 3) were cloned by screening an A. marmorata cDNA library. Tissue distribution analysis of Western blot showed that Cacnb1, 2, 3 had a significantly high expression in gill; while mRNA results showed the expressions of cacnb1 and cacnb3 were predominated in skin tissue but only cacnb2 was expressed in intestine. Serum osmolality and Ca concentrations of A.marmorata were increased in a high calcium environment while reduced in a low calcium environment within 7 days; however, they were not significantly different among Ca treatments after the eels were acclimated for 7 days. We also examined the influence of ambient Ca levels on cacnbs expression of eels. With the increasing of exposure time, mRNA and protein expressions of cacnb1 were up-regulated in high level of Ca (10 mM) and down-regulated in deficient Ca (0 mM) compared to the control Ca (2 mM). However, the opposite results were observed in cacnb2 and cacnb3. Notably, the cacnb2 expression was not significant different among Ca treatments on day 7. Our study provided the insightful evidence that cacnbs play important roles in maintaining Ca homeostasis of fish.