AUTOREGULATION OF RENAL BLOOD FLOW

ABSTRACT

Renal blood flow (RBF) autoregulation basically is a vital homeostatic mechanism that protects the kidney from elevations in arterial pressure that would be transmitted to the glomerular capillaries and cause injury (Marylin et al., 2014). It also allows the kidney to maintain a relatively constant blood flow and glomerular filtration rate (GFR) necessary for the clearance of metabolic wastes while maintaining efficient recovery of filtered electrolytes and nutrients by the renal tubules. These mechanisms include myogenic control mechanism which maintains flow over a varying range of pressures, and the tubuloglomerular feedback mechanism. Autoregulation of renal blood flow is caused by the myogenic response (MR), tubuloglomerular feedback (TGF) and a third regulatory mechanism that is independent of TGF but slower than MR (Armin, 2007). Elevations in vascular resistance, especially in renal circulation, are characteristic of hypertension. The myogenic mechanism regulating blood flow within the kidney depends upon a characteristic shared by most smooth muscle cells of the body. When one stretches a smooth muscle cell, it contracts; when stopped, it relaxes, restoring its resting length. It can also be demonstrated in the autoregulation of the mesenteric, skeletal muscle, cerebral, renal, and coronary circulation (Gerald and Linda, 2004). Tubuloglomerular feedback serves as an effective autoregulatory mechanism because the sodium chloride concentration of the fluid reaching the macula densa is dependent on flow rate, which in turn, is related to the GFR and glomerular capillary pressure. The kidney displays highly efficient autoregulation so that under steady-state conditions renal blood flow (RBF) is independent of blood pressure over a wide range of pressure (Mathias et al., 2015.