Angiotensinogen from liver, Renin from JGA, Converting enzyme in lung, Angiotensin I, Angiotensin II, Aldosterone, Na+ and H2O retention, Increased blood volume and pressure
H+ secretion is important in acid-base balance, K+ secretion is controlled by aldosterone, Organic anion and cation secretion helps eliminate foreign compounds from the body, Plasma clearance, the volume of plasma cleared of a particular substance per minute, is used to characterize secretion
Medullary vertical osmotic gradient is established by countercurrent multiplication with the thick ascending limb of the loop pumping NaCl out without water following, Interstitial NaCl build up draws water out of descending limb
Fluid passing down CD meets ever increasing medullary concentrations, therefore water removed by osmosis, water permeability of CD increases with presence of anti-diuretic hormone (vasopressin)
Measures relative water concentration of blood plasma (osmoreceptors in hypothalamus), brain secretes vasopressin from posterior pituitary gland in response to a decrease in body water content
In dehydration, triggers insertion of aquaporin water channels (AQP2) into epithelial membrane of collecting duct cells, water drawn out to conserve water (anti-diuresis), In overhydration, no vasopressin released, so water retained in collecting duct lumen, so water is then excreted from the body in urine (diuresis)
Different osmoconcentrating abilities among species depend on nephron anatomy and metabolic rates, Animals with long loops and high metabolic rates capable of highest levels of osmoconcentration
Other suggested explanations for the Inner Medulla Mystery: "Pelvic pumping" enhances concentration, external osmolytes (not yet tested), 3 counter-current systems in inner medulla