EFFECTS OF AVP AND DEOXYCORTICOSTERONE ON NA plus 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 Na-22+ (J1-->b and J(b-->1) in pmol.min-1.mm-1, respectively), hydraulic conductivity (P(f), mu-m/s), and transepithelial voltage (V(T), mV). J1-->b was 37.1 +/- 5.3 (mean +/- SE) in untreated rats and increased to 83.2 +/- 15.9 with AVP. V(T) 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 V(T) (-11.3 +/- 1.7); J1-->b and V(T) 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 J(b-->1), which ranged from 25 to 50. Benzamil reduced J1-->b to values not significantly different from J(b-->1), and V(T) became zero in CCDs treated with both AVP and DOC, indicating Na+ transport stimulated by both hormones occurs through apical membrane Na+ channels. P(f) 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.