Renal intracortical blood flow distribution, function and sodium excretion in response to saline loading of anesthetized and unanesthetized dogs

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Abstract
In order to study the effect of anesthesia on the canine response to saline loading, experiments were performed on 10 dogs, first while awake and then during pentobarbital anesthesia. Individual kidney function and intrarenal blood flow response to saline loading (7.5% body weight) were measured in each condition and all data are reported as the average of a single kidney. CIN is considerably reduced under anesthesia (24.7±3.2 vs. 43.2±3.9 ml/min,PIN or CPAH occurred in response to saline loading either in the anesthetized or unanesthetized state. The natriuresis was entirely due to a rise of CNA/GFR in both circumstances. The change of CNA/GFR in response to saline load was also appreciably larger while awake (1.2→4.7% vs. 0.7→1.8%). Although the fraction of blood flow to the outermost quarter of the kidney was initially the same (31±3 vs. 29±3%) awake or anesthetized, the changes with saline loading were in the opposite direction and the values reached were significantly different (37±3, awake, vs. 27±3%,P<0.05). We conclude that while increased outer cortical blood flow is not necessary for natriuresis, it may occur during sodium loading and may facilitate sodium excretion.