Signal transduction pathways of BK2 receptor in the renal glomerulus and mesangial cells: a mini review.

Using binding techniques we identified specific B2 kinin binding sites showing a pharmacological profile similar in glomeruli and in mesangial cell. Scatchard analysis revealed two classes of binding sites: a very-high-affinity site (Kd = 0.44 nM) and a high affinity site (Kd = 6.3 nM). Activation of the BK receptor of mesangial cells is associated with i) a transient dose-dependent increase in inositol 1,4,5 Triphosphate, ii) a biphasic rise in cytosolic free calcium, iii) a progressive secretion of PGE2, iv) an inhibition of the PGE2-stimulated increase of cAMP formation. All these effects were prevented by B2 antagonists. This multiple signal transduction pathway could suggest either heterogeneity in the BK receptor of the mesangial cell or different biological responses to be identified. Taken together, the results indicate that BK, at least in cultured cells, acts as a contractile effector, however, the physiological significance of a kinin receptor in the glomerulus remains to be elucidated.