Figure 16

Intrarenal responses to changes in arterial pressure at different levels of sodium intake. The renal autoregulation mechanism maintains the glomerular filtration rate (GFR) during changes in arterial pressure, GFR, and filtered sodium load. These values do not change significantly during changes in arterial pressure or sodium intake [3,16]. Therefore, the changes in sodium excretion in response to arterial pressure alterations are due primarily to changes in tubular fractional reabsorption. Normal fractional sodium reabsorption is very high, ranging from 98% to 99%; however, it is reduced by increased sodium chloride intake to effect the large increases in the sodium excretion rate. These responses demonstrate the importance of tubular reabsorptive mechanisms in modulating the slope of the pressure natriuresis relationship. (Adapted from Navar and Majid [9].)

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