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Renal sugar transport in the winter flounder IV. Effect of CA 2+ on sugar transport in teased renal tubules
Author(s) -
Kleinzeller Arnost,
Dubyak George R.
Publication year - 1977
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1040930103
Subject(s) - phlorizin , ouabain , sugar , chemistry , extracellular , galactose , brush border , sodium , sugar alcohol , biophysics , biochemistry , flounder , vacuole , intracellular , glucose transporter , membrane , endocrinology , biology , vesicle , insulin , organic chemistry , fishery , cytoplasm , fish <actinopterygii>
The electrolyte distribution and sugar uptake by teased renal tubules of winter flounder ( Pseudopleuronectes americanus ) was studied using incubation media with 1.4 mM Ca 2+ (controls) and without Ca 2+ . The omission of Ca 2+ : (a) produced some cellular swelling, and increase in cell Na + and loss of K + ; (b) had no effect on the extracellular propylene‐glycol space; (c) increased the uptake of non‐metabolizable methyl‐α‐D‐glucoside by the tissue: whereas in controls the equilibrium tissue/medium ratio (T/M) for the Na + ‐independent uptake of the sugar was 0.71 ± 0.03 (SEM, n = 9), in Ca 2+ ‐free media the T/M rose in 1.18 ± 0.06. The increase in sugar uptake seen in absence of Ca 2+ was abolished by absence of Na + (Li + ‐media), 0.5 mM ouabain and 0.5 mM phlorizin; (d) produced an increase in the galactose phosphate level without affecting that of free sugar; (e) decreased the active uptake of 2‐deoxy‐D‐galactose by the tubules. These results were analyzed on the basis of available information on the transport characteristics of the sugars at the luminal and antiluminal cell faces. It is suggested that absence of Ca 2+ increases the permeability of the intercellular junctions, thus permitting sugars to enter from the external medium into the tubular lumen. Methyl‐α‐D‐glucoside and D‐galactose can then be taken up into the cells by brush‐border localized active processes, whereas 2‐deoxy‐D‐galactose is not reabsorbed at this cellular face. At 1.4 mM Ca 2+ , the intercellular junction appears to be relatively impermeable to sugars and the transport properties in teased tubules reflect then events predominantly localized at the antiluminal cell face.