Date of Graduation


Document Type


Degree Name

Bachelor of Science

Degree Level



Biological Sciences


Tipsmark, Christian

Committee Member/Reader

Norman, Mya

Committee Member/Second Reader

Lessner, Daniel

Committee Member/Third Reader

McIntosh, Matt


Japanese medaka (Oryzias latipes) are euryhaline teleost and evolved divergently from the well-studied model organism zebrafish (Danio rerio). Claudins (cldns) are tight junction proteins known to regulate the permeability of the paracellular space, but little is known about the influence of the endocrine system on their regulation. In this study, in vitro gill culture model was used to test the effect of three osmoregulatory hormones (cortisol, growth hormone, and prolactin) on eight cldns previously identified in the gills of medaka. The stress hormone cortisol generally up-regulated the genes studied from 1.2- to 5-fold at the exceptions of cldn-28a and -28b. Growth hormone had little effect and only increased the transcription of cldn-10f 2.5-fold, while prolactin up-regulated the expression of cldn-28b, -10c, and -10f, to 2-, 2.5-, and 2-fold respectively. The results support the hypothesis that cldns-27a, -28a, -28b, and -30c are barrier-forming cldns, with -28b being induced by FW conditions. Further experiments need to be performed before the hormonal regulation of cldn-10 isoforms can be fully understood. The in vitro model shown here is a useful tool to resolve endocrine control of gill proteins involved in osmoregulation. Further investigation of the possible interactions of cortisol and prolactin or growth hormone would improve the understanding of claudin regulation by hormones.