| Autor: |
Musa-Aziz, Raif, Barreto-Chaves, Maria Luisa Morais, De Mello-Aires, Margarida |
| Zdroj: |
American Journal of Physiology - Renal Physiology; February 2002, Vol. 282 Issue: 2 pF256-F264, 9p |
| Abstrakt: |
10.1152/ajprenal.00056.2001. Peritubular arginine vasopressin (AVP) regulates bicarbonate reabsorption in the cortical distal tubule via V1and V2receptors. The dose-dependent effects of peritubular AVP on net bicarbonate reabsorption (JHCO3−) were evaluated by stationary microperfusion of in vivo early (ED; distal convoluted tubule) and late distal (LD; connecting tubule and initial collecting duct) segments of rat kidney, using double-barreled H+-sensitive, ion-exchange resin/reference (1 M KCl) microelectrodes. AVP (10−11M) perfused into peritubular capillaries increasedJHCO3−, compared with basal levels during intact capillary perfusion with blood, in ED and LD segments. AVP (10−9M) also increasedJHCO3−in both segments, but the effect of AVP (10−11M) was significantly higher. A specificV1-receptor antagonist alone or with AVP (10−11or 10−9M) reducedJHCO3−below basal levels. A specific V2-receptor antagonist alone or plus AVP (10−11M) did not affectJHCO3−but increased AVP (10−9M)-mediated stimulation. 8-Bromoadenosine 3′,5′-cyclic monophosphate alone reducedJHCO3−below basal levels and also reduced AVP (10−11M)-mediated stimulation. (Deamino-Cys1, d-Arg8) vasopressin (a V2-selective agonist) also reducedJHCO3−below basal levels. These results show that peritubular AVP stimulates JHCO3−in ED and LD segments via basolateral V1receptors and that basolateral V2receptors have a dose-dependent inhibitory effect mediated by cAMP. The data also indicate that endogenous AVP stimulates distalJHCO3−via basolateral V1receptors. |
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