Spironolactone antagonism of aldosterone action on Na+ transport and RNA metabolism in toad bladder epithelium

Epithelial cells of the toad bladder were disaggregated with EDTA, trypsin, hyaluronidase, or collagenase and were then scraped free of the underlying connective tissue. In most experiments EDTA was complexed with a divalent cation before the tissue was scraped. QOO2, sucrose and inulin spaces, and electrolytes of the isolated cells were measured. Cells disaggregated by collagenase or hyaluronidase consumed O2 at a rate of 4 µl hr-1 dry wt-1. QOO2 was increased 50% by ADH (100 U/liter) or by cyclic 3',5'-AMP (10 mM/liter). Na+-free Ringer's depressed the QOO2 by 40%. The QOO2 of cells prepared by trypsin treatment or by two EDTA methods was depressed by Na+-free Ringer's but was stimulated relatively little by ADH. Two other EDTA protocols produced cells that did not respond to Na+ lack or ADH. The intracellular Na+ and K+ concentrations of collagenase-disaggregated cells were 32 and 117 mEq/kg cell H2O, respectively. Cation concentrations of hyaluronidase cells were similar, but cells that did not respond to ADH had higher intracellular Na+ concentrations. Cells unresponsive to ADH and Na+ lack had high sucrose spaces and low transcellular membrane gradients of Na+, K+, and Cl-. The results suggest that trypsin and EDTA disaggregation damage the active Na+ transport system of the isolated cell. Certain EDTA techniques may also produce a general increase in permeability. Collagenase and hyaluronidase cells appear to function normally.

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THE EFFECT OF VALINOMYCIN ON THE TOAD BLADDER: ANTAGONISM TO VASOPRESSIN AND ALDOSTERONE

Journal of Endocrinology ◽

10.1677/joe.0.0450287 ◽

1969 ◽

Vol 45 (2) ◽

pp. 287-295 ◽

Cited By ~ 6

Author(s):

P. J. BENTLEY

Keyword(s):

Macrolide Antibiotic ◽

Short Circuit ◽

Short Circuit Current ◽

Water Transfer ◽

Toad Bladder ◽

Na Transport ◽

Bathing Medium ◽

Sodium Transfer ◽

Sites Of Action ◽

Subsequent Addition

SUMMARY The macrolide antibiotic valinomycin decreased short-circuit current (SCC, Na transport) across the isolated bladder of the toad. This effect was not overcome by increasing the K+ levels in the bathing medium or by the action of amphotericin B. The effects of vasopressin on both sodium and water transfer across the toad bladder were inhibited by valinomycin and the latter inhibition is non-competitive. The action of theophylline in increasing water transfer across the bladder was also inhibited. Cyclic AMP also increased water and Na+ transfer across the bladder but its action was not reduced by the macrolide. These results suggest that valinomycin inhibits adenyl cyclase. Aldosterone increases sodium transport across the toad bladder and this action was abolished by previous incubation of the tissue with the macrolide. Once the steroid-induced effect had been established subsequent addition of valinomycin did not alter the sodium transfer. Valinomycin thus appears to have several sites of action on the toad bladder.

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