The Endocrine Kidney: Local and Systemic Actions of Renal Hormones

The myriad physiologic functions of the kidneys are heavily regulated by the endocrine system. While extrarenal hormones exert well-recognized actions in the urinary system, in recent decades a host of intrinsic, renal hormones, with powerful effects on renal hemodynamics, glomerular filtration, and tubular electrolyte and water handling has been identified. Renal microcirculation, glomerular mesangium, and tubular epithelium produce angiotensin II, the natriuretic peptide urodilatin, vasoconstrictors endothelin-1 and urotensin II, and vasodilators adrenomedullin and intermedin. In addition, new details are emerging regarding the complex regulation of renal calcitriol production. The hematopoietic renal hormone erythropoietin has been found to mitigate ischemic injury to the kidneys, heart, and central nervous system. This chapter presents these products of the endocrine kidney and discusses their renal and systemic physiologic functions, their beneficial versus maladaptive contributions to renal diseases, and their potential exploitation to treat clinical disorders of the kidneys and other organs.