The circadian clock in the kidney.

Circadian variations in renal function were first described in the 19th century, and GFR, renal blood flow, urine production, and electrolyte excretion exhibit daily oscillations. These clinical observations are well established, but the underlying mechanisms that govern circadian fluctuations in kidney are not fully understood. Here we provide a brief overview of the machinery governing the circadian clock and examine the clinical and molecular evidence supporting a critical role for circadian rhythm in the kidney. There is a connection between BP oscillation and renal disease that supports the use of chronotherapy in the treatment of hypertension or correction of nondipping BP. Such studies support a developing model of clock controlled sodium and water transport in renal epithelial cells. Recent advances in identifying novel clock-controlled genes using rodent and cellular models also shed light on the molecular mechanisms by which the circadian clock controls renal function; however, the field is new and much more work remains.