Cellular basis of hormonal actions in the glomerulus.

Mesangial cells are contractile pericytes of the kidney glomerulus. Mesangial contraction/relaxation contributes to the regulation of glomerular hemodynamics. Additionally, mesangial cells process filtered macromolecules, synthesize extracellular matrix, respond to and release a number of cytokines and vasoactive mediators. Cultured mesangial cells express receptors for circulating and local agents that affect glomerular function. These receptors are coupled to distinct signaling pathways, namely phospholipase C and A2, transducing vasoconstrictor stimuli, and adenylate/guanylate cyclase, transducing vasodilators. Early intracellular signals include changes of cytosolic ions and cyclic nucleotides. They translate into short-term responses, such as cell depolarization and contraction, and later events, such as prostanoid synthesis and cell proliferation. Studies of mesangial cell behavior in culture may largely enhance our current understanding of glomerular pathophysiology.