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Cyst function in polycystic kidney disease: nongradient cysts
1Department of Medicine, New England Medical Center, Tufts University School of Medicine, Boston, MA 02111.
Clinical Nephrology
|September 1, 1989
Summary
Nongradient cysts from polycystic kidneys are nonfunctional. These non-gradient cysts exhibit passive sodium and chloride movement, unlike healthy kidney tubules.
Area of Science:
- Nephrology
- Cell Physiology
- Molecular Biology
Background:
- Previous studies showed active sodium transport in gradient cysts from polycystic kidneys.
- Nongradient cysts, failing to maintain sodium gradients, were poorly understood.
Purpose of the Study:
- To characterize the flux and electrical properties of nongradient cysts.
- To determine the transport mechanisms in nongradient cysts.
Main Methods:
- In vitro study of 23 nongradient cysts from human polycystic kidneys.
- Measurement of unidirectional ion fluxes (sodium and chloride) and electrical parameters (PD, Isc, conductance).
- Assessment of the effects of amiloride, ouabain, acetazolamide, and bumetanide.
Main Results:
- Nongradient cysts displayed low potential difference (PD), low short-circuit current (Isc), and high conductance.
- Sodium and chloride fluxes were high and highly correlated, suggesting passive, diffusional movement.
- Ion transport inhibitors had no significant effect on cyst function.
- Ionic permeability estimates were significantly higher than those of the proximal nephron.
Conclusions:
- Nongradient cysts are functionally impaired and do not perform active transport.
- Ion movement across nongradient cyst membranes appears to be passive via aqueous channels.
- These findings indicate a significant deviation from normal proximal nephron function in nongradient cysts.