Transepithelial water and urea permeabilities of isolated perfused Munich-Wistar rat inner medullary thin limbs of Henle's loop.

Transepithelial water and urea permeabilities of isolated perfused Munich-Wistar rat inner medullary thin limbs of Henle's loop. Am J Physiol Renal Physiol. 2013 Nov 6; Authors: Nawata CM, Evans KK, Dantzler WH, Pannabecker TL Abstract To better understand the role water and urea fluxes play in the urine concentrating mechanism, we determined transepithelial osmotic water (Pf) and urea (Purea) permeabilities in isolated perfused Munich-Wistar rat long-loop descending (DTL) and ascending (ATL) thin limbs. Thin limbs were isolated either from 0.5 to 2.5 mm below the outer medulla (OM) (upper inner medulla; IMupper) or from the terminal 2.5 mm of the IM (IMlower). Segment types were characterized on the basis of structural features and gene expression levels of the water channel aquaporin 1 (AQP1), which was high in DTLupper, absent in DTLlower, and absent in ATLs and the chloride channel ClCK1, which was absent in DTLs and high in ATLs. DTLupper Pf (μm/s) was high (32045 ± 450.28) whereas DTLlower showed very little or no osmotic water permeability (207.8 ± 241.3). Munich-Wistar rat ATLs have previously been shown to exhibit no water permeability. DTLupper Purea (x 10(-5) cm/s) was 40.0 ± 7.3 and much higher in DTLlower (203.8 ± 30.3), ATLupper (203.8 ± 35.7) and ATLlower (265.1 ± 49.8). Phloretin (0.25 mM) did not reduce DTLupper Purea, suggesting that Purea is not due to the urea transporter UT-A2, which is expressed in short-loop DTLs ...
Source: Am J Physiol Renal P... - Category: Urology & Nephrology Authors: Tags: Am J Physiol Renal Physiol Source Type: research