AJP - Renal Physiology, Vol 250, Issue 6 1082-F1089, Copyright © 1986 by American Physiological Society
Dissociation of urinary kallikrein activity and salt and water excretion in the rat
D. M. Pollock, M. I. Butterfield, J. L. Ader and W. J. Arendshorst
Experiments were designed to examine the relationship, if any, between
urinary kallikrein activity (amidolytic assay) and sodium and water
excretion in 12-wk-old Munich-Wistar rats. Five groups of animals were
studied: euvolemic, saline-expanded and water-loaded anesthetized rats, and
euvolemic and saline-expanded conscious restrained rats. Following surgery,
animals were allowed to stabilize (60-180 min) and reach a steady-state
urine flow. By design, basal sodium and/or water excretion varied markedly
among groups as a function of hydration state. Group means for sodium
excretion and urine flow ranged from 0.8 to 12.4 mu eq/min and 6 to 112
microliter/min, respectively. In contrast, neither active nor total urinary
kallikrein activity differed significantly among the five groups. In
anesthetized euvolemic rats, intravenous administration of aprotinin
produced a dose-dependent decrease in urinary kallikrein activity. The
greatest inhibition of 93 +/- 3% (active) and 72 +/- 10% (total) was
observed with a dose of 5,000 kallikrein inhibiting units (KIU)/kg and
1,000 KIU X kg-1 X min-1. This dose produced a significant decrease in
active and total kallikrein activity in each group (P less than 0.001).
However, sodium and water excretion were unchanged in aprotinin-treated
rats and similar to values in vehicle-treated time-control groups. Linear
regression analysis revealed no significant correlations between urinary
kallikrein activity and sodium excretion or urine flow either among or
within groups. These results indicate that urinary kallikrein activity is
not related to acute sodium and water homeostasis in anesthetized or
conscious rats.
