Hormonal regulation of aquaporin 3: opposing actions of prolactin and cortisol in tilapia gill

Abstract

Aquaporins (Aqps) are expressed within key osmoregulatory tissues where they mediate the movement of water and selected solutes across cell membranes. We leveraged the functional plasticity of Mozambique tilapia (Oreochromis mossambicus) gill epithelium to examine how Aqp3, an aquaglyceroporin, is regulated in response to osmoregulatory demands. Particular attention was paid to the actions of critical osmoregulatory hormones, namely, prolactin (Prl), growth hormone and cortisol. Branchial aqp3 mRNA levels were modulated following changes in environmental salinity, with enhanced aqp3 mRNA expression upon transfer from seawater to freshwater (FW). Accordingly, extensive Aqp3 immunoreactivity was localized to cell membranes of branchial epithelium in FW-acclimated animals. Upon transferring hypophysectomized tilapia to FW, we identified that a pituitary factor(s) is required for Aqp3 expression in FW. Replacement with ovine Prl (oPrl) was sufficient to stimulate Aqp3 expression in hypophysectomized animals held in FW, an effect blocked by coinjection with cortisol. Both oPrl and native tilapia Prls (tPrl 177 and tPrl 188 ) stimulated aqp3 in incubated gill filaments in a concentration-related manner. Consistent with in vivo responses, coincubation with cortisol blocked oPrl-stimulated aqp3 expression in vitro. Our data indicate that Prl and cortisol act directly upon branchial epithelium to regulate Aqp3 in tilapia. Thus, within the context of the diverse actions of Prl on hydromineral balance in vertebrates, we define a new role for Prl as a regulator of Aqp expression.

The osmorespiratory compromise in the euryhaline killifish: water regulation during hypoxia

“…1A,D), in general agreement with previous studies (Evans, 1969;Motais et al, 1969;Potts and Fleming, 1970;Isaia, 1984). This difference correlates with the lower expression of aquaporins in the gills reported in many studies, and may be an adaptation to counter the higher osmotic gradient between the environment and plasma in seawater (Isaia, 1984;Lignot et al, 2002;Cutler et al, 2007;Tipsmark et al, 2010;Madsen et al, 2015;Breves et al, 2016). The absolute values of k 3H2O measured in freshwater and seawater killifish were reasonably similar to values recorded in a variety of teleost species when adjusted for size and temperature Evans, 1969;Motais et al, 1969;Loretz, 1979;Onukwufor and Wood, 2018).…”

Osmoregulation in freshwaters: Gene expression in the gills of a Neotropical cichlid in contrasting pH and ionic environments

“…The effects of cortisol appear to be complex and context dependent, and increased cortisol levels are associated with both hyper- and hyposmotic challenge. In Omoss and Onil cortisol has been observed to both enhance, suppress, or act independently of the effects of prolactin or growth hormone on osmoregulatory proteins [47-49]. Consistent with this, cortisol appears to have been an important factor in both of our treatments, because the GO term response to corticosteroid appeared in the DE vs.…”

Pituitary Gonadotropins, Prolactin and Growth Hormone Differentially Regulate AQP1 Expression in the Porcine Ovarian Follicular Cells

“…In the literature, there is no data on the influence of PRL and GH on the expression of aquaporins in the porcine ovarian cells. The research concerns only the influence of these hormones on AQP3 expression in Mozambique tilapia ( Oreochromis mossambicus ) gill epithelium [ 59 ]. The authors in this study devoted attention to the effect of osmoregulatory hormones such as PRL, GH and cortisol on AQP3 expression.…”