American journal of physiology. Renal physiology
-
Am. J. Physiol. Renal Physiol. · Feb 2000
Mixed descending- and ascending-type thin limbs of Henle's loop in mammalian renal inner medulla.
Previous studies have generally indicated that the entire descending (DTL) and ascending thin limbs (ATL) of Henle's loops in the mammalian inner medulla exhibit structurally and functionally distinct properties. In the present study, we found that about 50% of Munich-Wistar rat inner medullary thin limbs, lying at positions distinctly above the bend, had segments exhibiting structural characteristics of DTL located immediately adjacent to segments exhibiting structural characteristics of ATL. Multiple DTL-type and ATL-type segments of variable length existed along a single straight portion of these mixed tubules. ⋯ Immunocytochemistry revealed expression of AQP1 in cells of pure DTL, but not pure ATL, and in cells of DTL-type, but not ATL-type, regions of mixed-type thin limbs. In contrast, the chloride channel ClC-K1 was expressed in pure ATL, but not pure DTL, and in ATL-type, but not DTL-type, regions of mixed-type thin limbs. Discontinuous axial expression of AQP1, UT-A2, and ClC-K1 along the straight portion of single thin limbs indicates that these nephrons possess a more heterogeneous structure than previously recognized.