Regulation of bicarbonate transporter cascade in the intestine of marine fish

Resumen

This thesis focused on the regulation of intestinal HCO3- secretion in the sea bream (Sparus aurata L.), by environmental challenges and endocrine factors. Taken as a whole I present below the main conclusions of the work: 1. A functional anterior–posterior specialization exits with regard to intestinal fluid processing and subsequently to salinity adaptation of the sea bream. In addition I describe a gain of function of the distal intestine, the rectum, at high salinities. 2. Calciotropic factors i.e. PTHrP and STC act as key regulators of carbonate aggregate formation in the intestine of the sea bream, via their actions on water absorption, calcium regulation and HCO3- secretion. 3. Calcium availability related either to salinity or feeding seems to play a key role on the regulation of intestinal physiology via the Calcium sensing receptor. 4. Ocean acidification, resulting from CO2 elevation, involves changes in pH that affect gene expression, acid-base regulation (ion movements and HCO3- secretion ) in the intestine of sea bream, that point to an increasing importance of fish socks to provide buffer capacity in the ocean.