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The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.

A fluorometric micromethod for the assay of Na-K-ATPase was used to determine Na-K-ATPase activity in 11 segments of the rabbit nephron. The Na-K-ATPase activity was found to be highest (greater than 100 pmol.mm1-.min-1) in proximal convoluted tubules (S1), medullary thick ascending limbs, distal convoluted tubules, and connecting tubules. There was a good correlation (r = 0.94) between Na-K-ATPase activity in different segments and net Na transport previously measured by in vitro tubule perfusion. Treatment of rabbits with deoxycorticosterone (DOCA) for 8-11 days produced increases in Na-K-ATPase activity of 100 and 500% in connecting tubules and cortical collecting ducts, respectively, without significant change in other segments. Maintenance on a low sodium diet for 12-18 days was associated with a 200% increase in Na-K-ATPase activity in cortical collecting ducts only. We conclude that the Na-K-ATPase activity is stimulated by mineralocorticoids in the cortical collecting duct in association with the previously observed changes in sodium transport.

Lactate production was measured directly in individual segments of the rat nephron. Tubules were dissected and then incubated in vitro with glucose as the only metabolic substrate. Each segment was incubated with and without antimycin A, an inhibitor of oxidative metabolism. Proximal tubules produced no lactate with or without antimycin A. The distal segments all produced lactate. The rate of lactate production without antimycin A ranged from 0.4 to 0.9 pmol X min-1 X mm-1 in all distal segments except one, the inner medullary collecting duct, which produced lactate at the significantly higher rate of 2.8 pmol X min-1 X mm-1. Antimycin A increased lactate production significantly in all of the distal segments. The increase was largest in medullary thick ascending limbs (1,400%) and cortical (798%) and outer medullary collecting ducts (357%). Increments were smaller in cortical thick ascending limbs (98%) and distal convoluted tubules (98%) and least in the inner medullary collecting ducts (28%). We conclude that lactate production occurs only in distal segments of the nephron and that under anoxic conditions significant amounts of ATP are produced by anaerobic glycolysis in these segments.

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