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Micropuncture studies of the proximal tubules suggest that fractional reabsorption is maintained at a constant level by the mechanism of glomerular–tubule balance, best explained at present by changes in intratubular volume which are proportional to and result from changes in the glomerular filtration rate. The precise role of the macula densa renin–angiotensin system in intrarenal regulation of sodium reabsorption has not been critically defined. The important factor in determining the value of fractional reabsorption in the proximal tubule appears to depend upon changes in body fluid volume balance, volume depletion enhancing the rate of reabsorption and volume expansion depressing it. Aldosterone may be an additional regulator of sodium reabsorption in the proximal tubules.
John H. Dirks (1968) studied this question.