AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 3 490-R497, Copyright © 1987 by American Physiological Society
Effects of dopamine in the renal vascular bed of fetal, newborn, and adult sheep
K. T. Nakamura, R. A. Felder, P. A. Jose and J. E. Robillard
The renal hemodynamic response to renal arterial dopamine infusions was
compared in unanesthetized fetal (129-137 days gestation, full term 145
days), newborn, and adult sheep. Mean arterial blood pressure and heart
rate remained unchanged during intrarenal dopamine infusions. Dopamine
produced dose-related decreases in mean renal blood flow velocity in all
three groups. When compared with adult sheep fetal sheep were slightly more
sensitive to the vasoconstrictive effects of dopamine ED50 (mean effective
dose ratio: fetus/ED50 adult = 0.368 +/- 0.047, P less than 0.05).
Increases in mean renal blood flow velocity were not seen at any dose given
(1-16 micrograms/kg body wt in fetuses, 2-32 micrograms/kg body wt in
newborns and adults) until dopamine was infused during alpha- and
beta-adrenoceptor blockade. The largest mean increase in renal flow
velocity was 13 +/- 3, 16 +/- 3, and 17 +/- 4% in fetal, newborn, and adult
sheep, respectively. cis-Flupentixol inhibited the vasodilation. This study
demonstrates the presence of renal vasodilation following renal arterial
dopamine infusions in fetal, newborn, and adult sheep when renal alpha- and
beta-adrenoceptors are blocked. Vasodilator responses are similar in all
three groups, and increases in renal blood flow velocity are small compared
with that of other experimental models.
