A B S T R A C T Previous studies in metabolic alkalosishave demonstrated that two factors are the prime determinants of acid excretion and bicarbonate reabsorption; first, the diversion to distal exchange sites of sodium previously reabsorbed in the proximal tubule and loop of Henle; and, second, a stimulus to sodium-cation exchange greater than that produced by a low-salt diet alone. In the present study we have examined the hypothesis that these two factors are also the prime determinants of acid excretion during the administration of mineral acid loads. To test this hypothesis, we have administered to dogs ingesting a low NaCl diet a daily dose of 7 meq/kg of H' with anions (chloride, sulfate, or nitrate) whose differing degrees of reabsorbability influence the speed and completeness with which each is delivered to the distal nephron with its accompanying Na'. After 2-3 wk of acid administration, and after an initial urinary loss of Na' and K+, the steady-state value for plasma [HCOs-] was 8.6 meq/liter below control in the HCl group, 3.7 meq/liter below control in the H2S04 group, and unchanged from control in the HNO3 group; all of these values were significantly different from each other.We would propose the following explanation for our findings: when HCl is administered chronically, marked acidosis occurs because distal delivery of Cl-is restricted by the ease with which the Cl-can be reabsorbed in the proximal portions of the nephron. Only when Cl-retention produces sufficient hyperchloremia to insure delivery of Na' (previously reabsorbed in proximal tubule and loop of Henle) to the distal nephron in quantities equal to ingested Cl is this primary constraint removed. In the case of sulfuric and nitric acids, there A preliminary report of this work was published in abstract form in J. Clin. Invest. 49: 40a (Abstr.). 1970.

PURPOSE:To investigate the effect of vardenafil in kidney of rats submitted to acute ischemia and reperfusion. METHODS:Twenty-eight rats were randomly distributed into two groups. Right nephrectomy was performed and the vardenafil group received vardenafil solution (at a concentration of 1 mg/ml in 10 mg/kg) while the control group received 0.9% saline solution (SS) one hour prior to the ligature of the left renal pedicle. After one hour of ischemia, animals were submitted to twenty-four hours of reperfusion, followed by left nephrectomy. The kidney's histological parameters evaluated on the study included vacuolar degeneration and tubular necrosis. Apoptosis was assessed by immunohistochemistry for cleaved caspase-3 using the point-counting and digital methods (Cytophotometry). Also, a biochemical analysis for creatinine was conducted. RESULTS:There were statistically significant differences between groups only with regards to the vacuolar degeneration parameter and to the cleaved caspase-3 digital method. CONCLUSION:Vardenafil showed a protective effect on the kidney of rats subjected to acute ischemia and reperfusion in this model