Effect of hexoprenaline on uteroplacental blood flow in the pregnant rat.

The effect of beta-adrenergic agonists on uteroplacental blood flow is controversial. Human studies, with the use of indirect methods to assess uteroplacental blood flow, show conflicting results. Animal studies in the near-term pregnant sheep model have the disadvantages that the sheep has a syndesmochorial placenta and that the uteroplacental vessels are thought to be maximally dilated near term. The effect of hexoprenaline, a new beta 2-sympathomimetic drug, was assessed in the awake pregnant rat on day 14 of gestation by means of the radionuclide-labeled microsphere method. Hexoprenaline increased placental blood flow by 198% and distribution of cardiac output to the placentas by 229%. Renal blood flow was reduced by 24%. Saline solution administration produced no significant effects.