Effects of AVP and deoxycorticosterone on Na+ and water transport in the Dahl salt-sensitive rat CCD.

Cortical collecting ducts (CCD) from inbred Dahl salt-sensitive rats were perfused in vitro to study effects of arginine vasopressin (AVP, present in the bath) and deoxycorticosterone pivalate (DOC) pretreatment on lumen-to-bath and bath-to-lumen fluxes of 22Na+ (J1----b and Jb----1 in pmol.min-1.mm-1, respectively), hydraulic conductivity (Pf, microns/s), and transepithelial voltage (VT, mV). J1----b was 37.1 +/- 5.3 (mean +/- SE) in untreated rats and increased to 83.2 +/- 15.9 with AVP. VT increased from -0.3 +/- 0.6 to -7.0 +/- 2.0. In DOC-pretreated rat CCDs, baseline J1----b was higher (85.1 +/- 7.6) as was VT (-11.3 +/- 1.7); J1b----b and VT were doubled with AVP addition (185.6 +/- 18.6 and -21.7 +/- 2.3, respectively). Thus J1----b in AVP-stimulated CCDs from untreated rats was not significantly different from control (no AVP) J1----b from DOC-pretreated rats; however, AVP produced a greater J1----b increase in the latter CCDs. Neither AVP nor DOC had an effect on Jb----1, which ranged from 25 to 50. Benzamil reduced J1----b to values not significantly different from Jb----1, and VT became zero in CCDs treated with both AVP and DOC, indicating Na+ transport stimulated by both hormones occurs through apical membrane Na+ channels. Pf increased from 59 +/- 80 to 1,072 +/- 176 with AVP addition to untreated rat CCDs and was unaltered by DOC or benzamil. Thus the Dahl rat CCD exhibits a transport response to AVP and DOC that is indistinguishable from that observed in Sprague-Dawley rats, as previously reported by this laboratory.