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1. It has been shown previously that low salt diet, confined to the perinatal period only, reduces blood pressure (BP) and sodium retention in spontaneously hypertensive rat (SHR) offspring at maturity when compared with those given high salt diet. 2. In this study it is shown that such high salt diets are associated with an increased level of circulating Na-K-ATPase inhibitor (CINK) activity. 3. Animals given perinatal high salt diet have a significantly greater tubular reabsorptive capacity when compared with those given low salt diet. 4. The finding of a high level of circulating Na-K-ATPase inhibitory material in the face of increased renal tubular capacity and blood pressure suggests that while this inhibitory material may play a role in the elevated blood pressure of animals given high salt diet, it cannot cause the elevated rate of fluid reabsorption.

1. The p-aminophenol (pAP) model of tubular necrosis displays elevated tubular pressures equivalent to 'stop-flow', with low glomerular filtration rate (GFR) but maintained blood flow and urine output. Renal function, micropuncture, and morphological studies were performed in anaesthetized rats to examine the causes of filtration failure. 2. At the height of pAP-induced renal failure proximal tubular fluid reabsorption (Jv(a] was markedly reduced while proximal and distal free-flow rates measured by tubular fluid collections during venting of the nephron were not significantly different from saline-injected controls. Renal blood flow was maintained over the 4 h observation period despite extensive and selective proximal tubular necrosis. There was no temporal relationship between increased tubular pressure and cast formation. 3. Maintained blood and tubular fluid flow rates indicate that activation of tubuloglomerular feedback plays little or no part in pAP-induced renal failure, which is apparently due to high fluid flow resistance in the region of the connecting tubule, late distal convolution or collecting ducts. Morphological appearances were consistent with compression of these segments.