Abstract
Summary
In the present study, the importance of the encephalorenal, spinal pathways in the kidney response to acute blood volume expansion (2.3% body wt) was examined. Studies were performed in conscious rats at least 2 hr after spinal transection at the C-8 level. The results were compared with those obtained from a series of similarly prepared rats which underwent an isovolemic, exchange transfusion to provide the control protocol. The increased urine flow, sodium excretion, glomerular filtration rate, tubular rejection fraction for sodium and mean arterial pressure were significantly different from those of the exchange-control series. The natriuresis was comparable to that for anesthetized, but untraumatized, normal rats which underwent a similar experimental protocol. The diuresis, however, was somewhat blunted perhaps attributable to a disparity in ADH levels as a result of the differences in anesthetic level and degree of surgical trauma.
It can be concluded that encephalorenal, spinal pathways are not essential for the renal reaction to an expanded intravascular volume. A correlation between the rise in urinary excretion and the rise in mean arterial pressure with infusion implicates intrarenal physical forces as one probable mechanism for the described responses.
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