Which of the following substances acts to increase the release of Ca2+ from endoplasmic reticulum?: (A) Inositol triphosphate, (B) Parathyroid hormone, (C) 1,25 dihydroxy cholecalciferol, (D) Diacylglycerol
Answer is A. Ans. A. Inositol triphosphateInositol triphosphate (IP3 ) and diacylglycerol (DAG) are second messengers for G protein coupled receptors. IP3 stimulates release of calcium from endoplasmic reticulum. DAG activates protein kinase C.