Recent trends in studies of the etiology of hypertension: Renal mechanism of blood pressure regulation

The kidney plays an important role in the control of systemic blood pressure by regulating the composition of body fluid and electrolyte and by producing and releasing various vasoactive substances such as renin-angiotensin and prostaglandins(PGs). The kidney possesses an intrinsic mechanism called 'pressure-natriuresis' in which an increase in perfusion pressure promotes natriuresis. According to this mechanism, hypertension can be classified as salt-sensitive or non-salt-sensitive based on the response to dietary sodium loading. Thus, a shift of the curve to the right and a decrease in the slope are the two basic abnormalities seen in the pressure-natriuresis relationship in hypertension, with each representing a different pathophysiology. In non-salt-sensitive essential hypertension, glomerular capillary pressure is within the normal range due to elevated preglomerular resistance, while it is elevated in salt-sensitive hypertension. Such differences may be reflected in the rate of progression of renal dysfunction as well as renal pathology. Finally, the mechanism responsible for the altered renal microcirculation involves dysregulation of intrinsic mechanisms(myogenic responses and tubuloglomerular feedback) as well as various local factors, in particular, angiotensin II, nitric oxide, and oxidative stress.