Importance of arachidonic acid as a mediator of parathyroid gland response.

The intracellular signaling mechanisms that mediate the regulation of parathyroid hormone (PTH) secretion by parathyroid glands are becoming increasingly more understood. Extracellular calcium modulates parathyroid function by acting on a G protein-coupled calcium-sensing receptor, which activates the hydrolysis of membrane phospholipids by phospholipases C, D, and A2 to generate intracellular signals. Arachidonic acid (AA) produced by phospholiphase A2 (PLA2) appears to play a crucial role throughout the generation of downstream-oxygenated products. Recent studies demonstrate the activation of the PLA2 via an intracellular calcium increase, and that the elevation of cytosolic calcium also overcomes the repressive effect of high extracellular phosphate on AA production. Furthermore, a role of the mitogen-activated protein (MAP) kinase cascade has also been documented in PLA2 activation.