Sodium and water transport in cortical collecting duct of Dahl salt-resistant rat
Kudo, L.H.; Hawk, C.T.; Schafer, J.A.
American Journal of Physiology 267(4 Pt 2): F583-F591
1994
ISSN/ISBN: 0002-9513 PMID: 7943356 Document Number: 429604
Studies were conducted to determine whether the cortical collecting duct (CCD) of the Dahl salt-resistant rat (inbred Rapp strain; R/Jr) exhibits the same responses to deoxycorticosterone (DOC; 2.5 mg as a depot injection in vivo, 3-8 days before experimentation) and arginine vasopressin (AVP, 220 pM in vitro) as the Sprague-Dawley (SD) (L. Chen, S.K. Williams, and J. A. Schafer. Am. J. Physiol. 259 (Renal Fluid Electrolyte Physiol. 28): F147-F156, 1990) and Dahl salt-sensitive (inbred Rapp strain, S/Jr) (C. T. Hawk and J. A. Schafer. Am. J. Physiol. 260 (Renal Fluid Electrolyte Physiol. 29): F471-F478,1991) CCD. Qualitatively, the R/Jr CCD responded as in the other two strains: AVP elevated the osmotic water permeability (P-f, mu-m/s) from 0 to - 1,200; either AVP or DOC, when used alone, increased the lumen-to-bath 22Na+ flux (J-l fwdarw -b, pmol cntdot min-1 cntdot mm-1) from the control range of 20-25 to - 40 and hyperpolarized the transepithehal voltage. AVP and DOC effects were synergistic, elevating J-l fwdarw -b to 90 +- 5 (mean +- SE) with both hormones, but this value was significantly lower than observed previously in both the SD and the S/Jr CCD, 125 +- 6 and 140 +- 6, respectively. However, bath-to-lumen fluxes (J-b fwdarw -l) were also significantly lower than observed in the SD and S/Jr CCD. Because net fluxes (J-net) in these experiments can be determined only as nonpaired differences between unidirectional fluxes, it is uncertain whether J-net values in the R/Jr CCD are significantly lower than in the SD or S/Jr CCD. Nevertheless, the lower unidirectional Na+ fluxes in the R/Jr CCD indicate that the transepithelial transport of this ion is different in the R/Jr than in the other two strains, a fact that may be associated with its resistance to the development of hypertension when placed on a high-salt diet.