Renal proximal tubule of flounder II. Transepithelial Mg secretion

Journal Article · Mon Mar 31 23:00:00 EST 1986 · Am. J. Physiol.; (United States)

OSTI ID:5532110

Cliff, W H; Sawyer, D B; Beyenbach, K W

The kinetics of transepithelial Mg secretion were studied in isolated perfused proximal tubule II of the flounder, Pseudopleuronectes americanus. To detect measurable changes of luminal (Mg) as a function of bath (Mg), the lumen had to be perfused at subnanoliter rates. Transepithelial Mg secretion did not obey first-order reaction kinetics; hence values for half saturation of transport (0.22 mM) and transport maximum (1.5 pmol X min-1 X mm-1) are apparent and suggest a high-affinity low-capacity transport system. Because all experiments were done in the absence of bath SO/sub 4/, the independence of Mg transport from SO/sub 4/ transport is established. In the absence of perfusion, when tubules secrete fluid spontaneously, secreted fluid contained Cl (156 +/- 3 mM), Na (130 +/- 6 mM), and Mg (27 +/- 5 mM), all significantly different from the bath. Rates of Cl, Na, and Mg secretion were all positively correlated with fluid secretion, but Na and Mg concentrations in secreted fluid were inversely proportional. The results indicate that NaCl secretion provides basal rates of fluid secretion, and when MgCl2 is secreted in addition, fluid secretion increases with the effect of generating inverse relationships between luminal Na and Mg concentrations.

• Research Organization: Cornell Univ., Ithaca, NY
• OSTI ID: 5532110
• Journal Information: Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States); ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ALKALI METALS
ALKALINE EARTH METALS
ANIMAL TISSUES
ANIMALS
AQUATIC ORGANISMS
BIOCHEMICAL REACTION KINETICS
BODY
CHLORIDES
CHLORINE COMPOUNDS
ELEMENTS
EPITHELIUM
FISHES
HALIDES
HALOGEN COMPOUNDS
IN VITRO
KIDNEYS
KINETICS
MAGNESIUM
MEMBRANE TRANSPORT
METALS
ORGANS
OXYGEN COMPOUNDS
PERFUSED ORGANS
REACTION KINETICS
SECRETION
SODIUM
SULFATES
SULFUR COMPOUNDS
TISSUES
VERTEBRATES