HORMONAL EFFECT ON THE OSMOTIC, ELECTROLYTE AND NITROGEN-BALANCE IN TERRESTRIAL AMPHIBIA

Two main hormones regulate water balance in amphibian. First, mesotoci n (MT) acting as a diuretic agent, and second arginine vasotocin (AVT) being an anti-diuretic hormone. In addition, prolactin (PRL), aldoste rone, corticosterone, angiotensin II and atriunatriuretic hormones, pl ay a role too in regulating water and ion balance. The hormones affect the epidermis and bladder permeability to water and ions as well as t he kidney through the control of the glomerular filtration rate (GFR). The main questions concern the presence and action of these hormones during the amphibian's life history. Are they present in both larval a nd adult stages? Are these hormones being synthesized in both aquatic and terrestrial adult phases? Under what circumstances are they being stored or released? Would the target organs (epidermis, bladder, kidne y) respond in a similar way during all periods? The problem is the fac t that under most circumstances an amphibian while in an aquatic envir onment responds physiologically differently than when on land. Only pa rtial information concerning hormone presence, release and control of water balance is available at the moment, and even that is fragmentary and based on only a very small number of amphibian species.