Nephrology Dialysis Transplantation, Vol 14, Issue 5 1124-1128, Copyright © 1999 by Oxford University Press
A Mandelbaum, E Podjarny, J Bernheim, J Green and M Rathaus
Background. Pregnant rats with adriamycin nephropathy
(ADRP rats) develop hypertension and have an increased vascular reactivity
to noradrenaline in the isolated mesenteric bed in
vitro. We have shown previously that the administration of
daltroban, a specific thromboxane receptor antagonist, prevented
hypertension in ADRP rats. Methods. We measured the
effect of daltroban (10-5 mol/l) on the
vasoconstrictory response to noradrenaline (1-10 &mgr;mol/l) in the
isolated mesenteric bed of ADRP rats at the end of pregnancy, as compared
with normal pregnant and adriamycin-treated virgin rats. In further
experiments, we measured the changes of flow induced by increasing
concentrations of the thromboxane analogue, U46619
(10-7-10-6 mol/l). Finally,
changes of flow were assessed in arteries maximally constricted with U46619
(10-6 mol/l) during perfusion in the presence of
increasing concentrations of daltroban
(10-7-10-5 mol/l).
Results. Daltroban diminished the response to
noradrenaline in all groups, shifting the concentration-effect curve to the
right. However, at maximal concentrations of noradrenaline, daltroban was
ineffective in all rats, except in ADRP animals. The vasoconstrictory
response to U46619 was significantly reduced in all pregnant rats, both
normal and adriamycin-treated. Daltroban progressively released the
vasoconstriction induced by U46619 in all groups. However, this vasodilator
response was attenuated in the adriamycin-treated rats, the slopes of their
curves being smaller than those of the respective untreated groups
(0.038±0.006 in virgin rats vs
0.063±0.011 in controls, P<0.05; and
0.015±0.005 in ADRP vs
0.028±0.008 in normal pregnancy,
P<0.05). Conclusions. The
findings could be explained by enhanced occupancy of thromboxane receptors
by an endogenous agonist, possibly PGH2, as a consequence of either
increased levels of the autacoid or increased number of affinity receptors.
Keywords: daltroban; mesenteric arteries; thromboxane
receptor antagonists
ORIGINAL ARTICLES
Role of thromboxane in the altered vascular reactivity of pregnant rats with adriamycin nephropathy
Department of Nephrology, Meir Hospital, 44281 Kfar Saba, Israel; Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel; Corresponding author
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