Compensatory hypertrophy and adaptation in the cortical collecting duct

The cortical collecting duct (CCD) undergoes hypertrophy and functional adaptation following reduction of renal mass. The nature and mechanisms of these changes have been investigated using microperfusion of isolated CCD from rabbit remnant kidneys. By 1 week after reduction of renal mass, tubule hypertrophy and increased sodium transport are fully developed. The transport adaptations are specific or selective, since bicarbonate transport in these CCD is unchanged. Mineralocorticoids may play an important role in the hypertrophy and increased sodium transport, since plasma aldosterone increases early after reduction of renal mass. Also, adrenalectomy abolishes the changes in size and sodium transport, even with supplementation of aldosterone to unstressed physiologic levels. Epidermal growth factor also has immediate effects on CCD sodium transport; however, the direction of the effect is opposite--an inhibition of transport.