Expression of endocrine genes in zebrafish larvae in response to environmental salinity

Abstract

We tested the capability of the endocrine system in zebrafish to respond to environmental salinity challenges during larval stages. We reveal that the zebrafish larvae have a system in which several endocrine genes, including atrial natriuretic peptide (anp), renin, prolactin, growth hormone ( gh) and parathyroid hormone 1 (pth1), respond at the transcription level to changes in environmental salinity and that the responses are gene specific. Both anp and renin are upregulated in larvae raised in dilute freshwater medium but are downregulated in concentrated medium. On the other hand, expression of prolactin and gh is strongly enhanced in the dilute medium, but shows little or no change under higher salinity conditions. Interestingly, PTH1 expression depends on Ca 2C concentration, as observed in mammals. Thus, taken together with the advantages of a model organism, including accessibility to genetic approaches, we propose that zebrafish larvae are useful for a comprehensive study of the regulatory mechanisms of the endocrine system in ionic and osmotic homeostasis.

Renin expression in developing zebrafish is associated with angiogenesis and requires the Notch pathway and endothelium

“…Salinity solutions were prepared as previously described (24,60). Captopril (C4042, Sigma-Aldrich) was administered at 0.1 mM.…”

“…If functionally conserved, the fish RAS may also function in ion homeostasis and development. The zebrafish pronephros is functional from 76 hours postfertilization (hpf) (13), and recent studies in fish have suggested that larval renin (24) and the RAS (35) may be involved in ion homeostasis. Canonical ANG II-mediated Na ϩ uptake via aldosterone activation of the epithelial Na ϩ channel in the distal nephron of mammals may differ in zebrafish, which lack aldosterone synthase.…”

Neuroendocrine control of ionic balance in zebrafish

“…The physiological role of the RAS in fish is not completely understood. Nevertheless, increasing evidence suggests that the RAS is involved in osmoregulation (Fuentes and Eddy, 1997;Hoshijima and Hirose, 2007;Kumai et al, 2014a;Smith et al, 1991). It is well documented that ANG-II promotes drinking in euryhaline fish (Beasley et al, 1986;Carrick and Balment, 1983;Fuentes and Eddy, 1996;Kobayashi et al, 1983), potentially increasing salt absorption from the gut.…”

Angiotensin-II promotes Na+ uptake in larval zebrafish, Danio rerio, in acidic and ion-poor water

“…Smith et al (1991) reported a decline in plasma renin activity in freshwateracclimated rainbow trout fed with a salt-enriched diet, suggesting a possible role for ANG-II in the regulation of salt balance in freshwater fish. Subsequently, Hoshijima & Hirose (2007) reported an increase in renin mRNA expression during acclimation of zebrafish to ion-poor water (20-fold dilution of the control water), suggesting a role of the RAS in promoting salt absorption. Despite these studies, the question of whether the RAS promotes salt uptake in freshwater fish remains unexplored.…”