AJP - Regulatory, Integrative and Comparative Physiology, Vol 245, Issue 1 69-R75, Copyright © 1983 by American Physiological Society
Stimulation of urinary acidification by insulin in the turtle bladder
J. A. Arruda
Addition of insulin to the substrate-containing serosal solution of freshly
excised bladders or to that of bladders incubated overnight in
substrate-enriched media increases the rate of H+ secretion to a greater
extent in the latter (overnight group) than in the former. This effect can
be blocked by pretreatment with anti-insulin antibody, suggesting that the
stimulation of H+ secretion is a specific effect of insulin. The effect of
insulin is concentration dependent with half-maximal stimulation of H+
secretion at 100 mU/ml and maximal stimulation at 250 mU/ml. Other
characteristics of the insulin-induced stimulation of H+ secretion were its
independence of any effect of Na transport and its absolute requirement for
the presence of substrate (glucose or pyruvate) under aerobic conditions
only. The proton-secreting action of insulin is associated with an increase
in the proton-selective conductance in series with the proton pump while
the estimated electromotive force of the proton pump remains constant.
Finally, the insulin-induced and aldosterone-induced stimulations of proton
secretion are mutually independent, as shown by the additivity of these
events and by the fact that the effect of insulin was not blocked by
pretreatment with cycloheximide. These data suggest that endogenous insulin
modulates the rate of H+ secretion by the in vivo turtle bladder.
