Micropuncture experiments on distal convoluted tubules indicate that parathyroid hormone and cyclic AMP enhance calcium reabsorption in this nephron segment. Changes in colloid osmotic pressure in the vascular perfusate of isolated perfused rat kidneys led to parallel changes in absolute fluid reabsorption by pump perfused proximal tubular segments of such kidneys. Lowering of peritubular sodium concentration results in a reduced hydro-osmotic response of cortical collecting tubules. A similar maneuver in proximal convoluted tubules (isolated perfused proximal tubules) reduces net reabsorption of sodium and of water.

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National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases (NIADDK)
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General Medicine B Study Section (GMB)
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Weill Medical College of Cornell University
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Frindt, G; Sackin, H; Palmer, L G (1990) Whole-cell currents in rat cortical collecting tubule: low-Na diet increases amiloride-sensitive conductance. Am J Physiol 258:F562-7
Frindt, G; Windhager, E E (1990) Ca2(+)-dependent inhibition of sodium transport in rabbit cortical collecting tubules. Am J Physiol 258:F568-82
Lin, J T; Xu, Z J; Lovelace, C et al. (1989) Effect of Ca on Na-D-glucose cotransport across isolated renal brush-border membranes. Am J Physiol 257:F126-36
Palmer, L G; Frindt, G (1988) Conductance and gating of epithelial Na channels from rat cortical collecting tubule. Effects of luminal Na and Li. J Gen Physiol 92:121-38
Jones, S M; Frindt, G; Windhager, E E (1988) Effect of peritubular [Ca] or ionomycin on hydrosmotic response of CCTs to ADH or cAMP. Am J Physiol 254:F240-53
Windhager, E E; Yang, J M; Lee, C O et al. (1988) Measurements of aiCa, aiNa and membrane potential and patch clamp studies of the effect of changes in aiCa on Na channel activity in renal tubules. Prog Clin Biol Res 252:203-7
Yang, J M; Lee, C O; Windhager, E E (1988) Regulation of cytosolic free calcium in isolated perfused proximal tubules of Necturus. Am J Physiol 255:F787-99
Palmer, L G; Frindt, G (1987) Effects of cell Ca and pH on Na channels from rat cortical collecting tubule. Am J Physiol 253:F333-9
Frindt, G; Palmer, L G (1987) Ca-activated K channels in apical membrane of mammalian CCT, and their role in K secretion. Am J Physiol 252:F458-67
Lorenzen, M; Frindt, G; Taylor, A et al. (1987) Quinidine effect on hydrosmotic response of collecting tubules to vasopressin and cAMP. Am J Physiol 252:F1103-11

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