The pituitary gland and plasma were collected and analysed. After restoration of water temperature to normal the cortisol level returned to normal levels. This response is evidence that a cold shock activates the HPI-axis. The renin angiotensin system is responsible for a wide range of physiological effects involved in water and electrolyte balance. These responses, at least in mammals, include actions on blood pressure, steroidogenic function, renal function although its precise role in lower vertebrates is as yet unclear.
Elasmobranchs possess a unique salt secreting gland, the rectal gland.
The effect of df Ang II on the secretion rate was investigated using an isolated perfused rectal gland preparation. This study indicates a physiological role for df Ang II in cardiovascular responses and fluid and electrolyte balance in elasmobranchs. While glomerular ANG II receptors have been demonstrated, their intracellular signalling is unknown. These results demonstrate functional AT 1 -like ANG II receptors, linked to intracellular calcium signalling, in glomeruli of euryhaline teleosts. To elucidate the modulatory role of NO and ET1 for renal sodium and water excretion in the Pekin duck, physiological studies were combined with radioligand binding techniques.