HYPERTONIA ÉS NEPHROLOGIA - eLitMed.hu

2002; 6 (1):3–15. ONTOGENY OF POTASSIUM TRANSPORT IN THE DISTAL NEPHRON 5
at high rates (Fig. 1) (4; 10; 11). Transepithelial net K +
secretion can be further stimulated as the tubular fluid flow
rate increases (Fig. 2) (10), as has been reported by others (3;
4; 9). In contrast, net K + transport is not detected in
CCD
K
Cl -
H
NACl
K
-
HCO3 Na +
K +
-
HCO3 -
Cl -
K +
microperfused CCDs from newborn rabbits until the third
week of postnatal life (Fig. 1) and can not be elicited by
increasing tubular fluid flow rate in the first month of life (Fig.
2) (10).
(ENaC)
H +
K +
H +
H +
Cl -
principal
cell
-intercalated
cell
-intercalated
cell
Figure 3. K + and Na + transport pathways in the fully differentiated CCD, a nephron segment comprised of principal
and intercalated cells. The apical Na + (ENaC) and K + channel(s) in the principal cell are considered to represent the
rate-limiting steps in transepithelial Na + absorption and K + secretion, respectively. Predicted from this model is that
K + secretion will cease in the absence of Na + absorption
Na +
K +
-
HCO3 Cl -
Cl -
K +
Cl -
H +