Table 1.
Base-case transtubular transport parameters
| Pf, μm/s | PNa,10−5 cm/s | Purea, 10−5 cm/s | Vmax,Na, nmol·cm−2·s−1 | |
|---|---|---|---|---|
| LDL2S | 0 (45) | 0 (45) | 1 | 0 |
| LDL2 | 2,200 (14) | 0 (45) | 13 (40,68) | 0 |
| LDL3 | 0 | 0 (45) | 1 | 0 |
| ATLS* | 0 (14) | 80 (14) | 1 | 0 |
| ATLM* | 0 (14) | 80 (14) | 1 | 0 |
| ATLL* | 0 (14) | 80 (14) | 1 or 20† | 0 |
| CD | 460→750§ (55) | 1 (57) | 1 to 90§ (18, 56) | 10.5→5→3§ (72) |
| DVR | 1,257 (42) | 76 (44) | 360 (44) | 0 |
| AVR | 750 | 690 | 0 |
Parameters are given by, based on, estimated from, or suggested by references given in parentheses. P, premeability; Pf, osmotic water permeability coefficient, ATL, ascending thin limb; LDL, segment of a descending thin limb; CD, collecting duct; DVR and AVR, descending and ascending vasa recta, respectively.
A prebend segment is assumed to have the same transport parameters as its contiguous ATL.
The higher urea permeability (20 ×10−5 cm/s) applies only to the upper 40% of the ATLL; the urea permeability of the lower portion of the ATLL is 1×10−5 cm/s. ‡Parameter increases exponentially as medullary depth x increases from 1.0 to 5.0 mm.
Arrows indicate that parameter varies linearly between the given values as medullary depth x increases; see details in text.