Altered contractility of urinary bladder in the diabetic rabbit:
relationship to reduced na + -pump activity.
Gupta, Sandeep, Stone Yang, Richard A. Cohen, Robert J. Krane, and
I[tilde]nigo Saenz De Tejada.
DEPARTMENT OF UROLOGY AND VASCULAR BIOLOGY UNIT, BOSTON UNIVERSITY
SCHOOL OF MEDICINE, BOSTON, MA 02118
APStracts 3:0267C, 1996.
We studied the effect of alloxan-induced diabetes on Na+-pump activity
in isolated rabbit bladder strips. In addition, the effects of
diabetes and the Na+-pump inhibitor, ouabain, on contractions induced
by carbachol (Cch) and potassium chloride (KCl) were studied. In
bladder strips from diabetic rabbits, ouabain-sensitive 86Rb-uptake
(OS; a measure of Na+-pump activity) was approximately 50% less
compared to strips from normal bladder. Diabetes also reduced maximum
contractions induced by Cch and KCl. Treatment of bladder strips with
ouabain alone caused an acute concentration-dependent increase in
tone. In contrast, longer incubation with ouabain inhibited Cch and
KCl-induced contractions in normal and diabetic bladders.
Furthermore, differences in agonist-mediated contractions observed
between normal and diabetic bladders were abolished in the presence
of the maximally effective concentration of ouabain (10 [mu]M). The
ability of Cch to cause contraction in normal and diabetic rabbit
bladders was also significantly inhibited by the Na+-ionophore,
monensin, but not by the Ca2+ ionophore, A23187, or upon
depolarization with KCl. Monensin also inhibited KCl-induced
contractions in normal bladder strips. These results indicate that i)
Na+-pump activity is an important modulator of bladder smooth muscle
tone; ii) diabetes diminishes Na+-pump activity and inhibits agonist
-induced contractions in bladder; iii) an increase in intracellular
Na+-concentration, secondary to inhibition of bladder smooth muscle
Na+-pump activity, is associated with reduced responsiveness to
contractile agonists. Diminished Na+-pump activity in diabetes may,
in part, contribute to the development of bladder cystopathy.
Received 9 July 1996; accepted in final form 24 May 1996.
APS Manuscript Number C289-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996