AJP - Renal Physiology, Vol 248, Issue 1 70-F77, Copyright © 1985 by American Physiological Society
Crystal accumulation and very high short-circuit currents in rabbit urinary bladder
D. D. Loo and J. M. Diamond
We describe a condition in rabbits characterized by CaCO3 crystal
accumulation and very high short-circuit current (Isc) in the urinary
bladder. The incidence of the condition was high in rabbits kept for 2 mo
or more in the vivarium. The crystal mass in the bladder increased with age
or time until it occupied up to one-third of the bladder volume and
occasionally aggregated as stones, and the urine attained a sludgy
consistency. In animals with sludgy urine, the urine excreted had a crystal
content 20 times lower than that of urine contained in the bladder at time
of death, implying retention of crystals in the bladder. Kidney stones were
not detected in rabbits with bladder crystals, and bladder crystals were
absent in rabbits with kidney stones induced experimentally by uremia. In
old rabbits with sludgy urine the Isc, a measure of Na+ transport, was up
to 46 microA/cm2 and averaged 12 microA/cm2, seven times the Isc of rabbits
with nonsludgy urine. The increased Isc was entirely amiloride sensitive.
Noise analysis showed it to arise entirely from increased channel density,
without change in single-channel current. With one possible exception, we
could not find bacterial infection or abnormalities in plasma aldosterone,
GFR, or urinary [Na+], [Ca2+], pH, or osmolality that could explain the
condition. The exception is that some unidentified component accounting for
half the osmolality of nonsludgy urine is absent or at low concentration in
sludgy urine. It remains unknown why the condition develops and whether
CaCO3 crystals cause high Isc or vice versa or whether both result from a
third factor.
