Question

Which of the following statements regarding vasopressin are correct? Select all options that apply:

(a) Vasopressin is synthesized in the posterior pituitary

(b) Vasopressin secretion increases when plasma osmolarity is greater than 0.28 OsM

(c) Vasopressin binds to receptors on the basolateral membrane of collecting duct cells

(d) Vasopressin increases the amount of aquaporins on the apical membrane of collecting duct cells

(e) Vasopressin does not affect the amount of aquaporins on the basolateral membrane of collecting duct cells

Answer 1

Vasopressin is synthesised in the supraoptic nucleus of hypothalamus and stored in the posterior pitutary.vasopressin secretion increase when the plasma osmolarity increases above the 280mOsm/kg or 0.28Osm/kg.It principally act on the basolateral membrane in the collecting ducts ,activating the adenylate cyclase and a synthesis of cAMP.which in turn activates protein kinase A , protein kinase A phosphorylate the aquaporin channels which allow the cell to absorb water passively under the concentration gradient of sodium .

Thus Statement B ,C and D are correct .A and E are not correct.