Figure 3. Schematic of hormone actions on the various aspects of ion regulatory processes. Different hormones differentially affect ionocyte number (cell proliferation, specification, and differentiation), transporter abundance (expression of transporter), and activity (post-translational regulation). Dashed lines and the question mark indicate that the transporters regulated by specific hormone are yet to be identified. Ionocyte specification and differentiation are presented as a simplified depiction modified from Hwang and Chou (2013); for details, refer to the text. For the ionocytes and related transporters, refer to Fig.1. IC, ionocyte; KC, keratinocyte; STC-1, stanniocalcin-1; PRL, prolactin; PRLRA, prolactin receptor A; PTH1, parathyroid hormone 1; VitD, vitamin D; VDRa, vitamin D receptor A; CT, calcitonin; CTR, calcitonin receptor; ANGII, angiotensin II; EDN1, endothelin-1; EDNRAa, endothelin receptor Aa.