Systemic versus tissue-level prolactin signaling in a teleost during a tidal cycle

AbstractEuryhaline Mozambique tilapia (Oreochromis mossambicus) are native to estuaries where they encounter tidal fluctuations in environmental salinity. These fluctuations can be dramatic, subjecting individuals to salinities characteristic of fresh water (FW  <  0.5‰) and seawater (SW 35‰) within a single tidal cycle. In the current study, we reared tilapia under a tidal regimen that simulated the dynamic conditions of their native habitat. Tilapia were sampled every 3 h over a 24 h period to temporally resolve how prolactin (PRL) signaling is modu lated in parallel with genes encoding branchial effectors of osmoregulation. The following parameters were measured: plasma osmolality, plasma PRL177 and PRL188 concentrations, pituitaryprl177 andprl188 gene expression, and branchialprl receptor (prlr1 andprlr2),Na+/Cl−-cotransporter (ncc2),Na+/K+/2Cl−-cotransporter (nkcc1a),Na+/K+-ATPase (nka α1a andnka α1b),cystic fibrosis transmembrane regulator (cftr), andaquaporin 3 (aqp3) gene expression. Throughout the 24  h sampling period, plasma osmolality reflected whether tilapia were sampled during the FW or SW phases of the tidal cycle, whereas pituitaryprl gene expression and plasma PRL levels remained stable. Branchial patterns ofncc2, nkcc1a, nka α1a,nka α1b, cftr, andaqp3 gene expression indicated that fish exposed to tidally changing salinities regulate the expression of these gene transcripts in a similar fashion as fish held under static SW conditions. ...
Source: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology - Category: Physiology Source Type: research