What hormones are acting in the nephrons and their modes of action?
Answer - 1)Diuretics and renal harmones in nephrons
1)Angiotensin II- in the proximal convulated tubules of the kidney angiotensin II acts to increase Na-H exchange , increasing sodium reabsorption , increased level of Na in the body act to increase osmolarity of the blood leading to shift of fluid into the blood volume and extracellular space this increase the arterial pressure of the pateint .It also act on adrenal cortex specifically to the zona glomerulosa it stimulates the release of aldosterone . aldosterone is a steroids harmones that causes an increase in sodium reabsorption and potassium excretion at the distal tubule and collecting duct of nephrons . Finally angiotensin II act on the brain .
2)Antidiuretic harmones=ADH principally exert it's effect by binding to principle cell within the late distal tubule and collecting duct with our kidney nephrons .ADH bind to the V receptors on these cell which is coupled to G .These ligation events lead to G activation of adenylate cyclase which causes the suquently increase the second messenger cyclic AMP (cAMP) . cAMP activates protein kinase A (PKA) a phoshorylating enzyme that initiates intracellular phoshorylation cascade . Intracellular aquaporins -2 (AQP2) storage vesicle are phoshorylted which promotes their movement and insertion into the apical membrane . (AQP2) it is Water channel that allow Water to move passively into the cell guided by the osmotic gradient established NaCl and urea and promotes reabsorption water in the kidney .
It also has second action on vascular smooth muscle .ADH bind to V receptors on vascular smooth muscle and activate G protein . G activates phospholipase C which result in production of inositol triphosphate (IP3) as well as diacylglycerol (DAG) from the cell membrane .IP3 causes a release of intracellular calcium from the endoplasmic reticulum DAG and calcium activate protein kinase C (PKC) which like PKA result in signaling phosphorylation cascade . The net effect in signaling cascade is contraction of vascular smooth muscle leading to increase in total peripheral resistance and thus increase in blood pressure .
3) Parathyroid harmone =it regulate serum calcium through its effect on bone , kideny and intestines .In bone PTH enhance the release of calcium from large reservoir contained in the bone .
It act on ascending limb of loop of Henal and DCT . Parathyroid harmone increase Ca2+ Absorption in the cortical portion of thick ascending limb of the Henal loop in both distal convulated and collecting tubule cell Parathyroid harmone regulate transcellular Ca2+ Absorptions by controlling the insertion and open probability of luminal plasmalemmal Ca2+ ion channel .