Heterogeneity of the XXXX collecting tubule: localization of mineralocorticoid hormone action to the cortical portion.

@entity972 @entity1372 @entity95 @entity8147 @entity2865
This study was designed to examine the @entity1372 , @entity972 , and @entity2865 transport rates across the cortical and outer medullary collecting tubule and to localize the action of mineralocorticoid hormone. @entity95 collecting tubules were dissected from the cortex (CCT), the outer stripe of the outer medulla (OMCT0), or the inner stripe of the outer medulla (OMCTi). From normal @entity95 , the transepithelial voltage was -20.8 +/- 2.7 mV in CCT, -4.2 +/- 1.4 mV in OMCT0, and +10.6 +/- 2.3 mV in OMCTi. From @entity8147 -treated @entity95 , only the CCT voltage was different (-42.9 mV). Net @entity1372 absorption across the CCT increased ith @entity8147 -treatment from 23 +/- 5 to 54 +/- 8 pEq . mm-1 . min-1, whereas net @entity972 secretion increased from 15 +/- 2 to 43 +/- 5 pEq . min-1 . min-1. Net @entity2865 absorption was significant only in @entity8147 -treated @entity95 . The OMCTi, in contrast, displayed no net transport of @entity1372 , @entity972 , or @entity2865 and had a lower rate coefficient for @entity1372 efflux than did the CCT. @entity8147 treatment had no effect on any transport rate measured in this segment. The OMCT0 has small @entity972 secretion, which did not increase with @entity8147 treatment. The collecting tubule is heterogeneous along its length with respect to ion transport. Mineralocorticoid-hormone-sensitive @entity1372 absorption is present predominantly, if not exclusively, in the cortical collecting tubule.
