Modification of the Depressor Response to Arachidonic Acid in Dogs by Gonadal Steroids

Abstract

Summary

Single intramuscular injections of either progesterone (2 mg/kg), estrogen (1 mg/kg), testosterone (10 mg/kg), or vehicle (control) were given to mongrel dogs of both sexes. Arachidonic acid (100 and 200 μg/kg), PGE₂ (0.025, 0.05, 0.1, 0.25 ia and 1-3 μg/kg iv), and PGF₂α (1 μg/kg ia and 5 μg/kg iv) were injected into the inferior vena cava (iv) or left ventricle (ia) 68-90 hr after hormone treatment. Changes in the systemic pressure responses were observed. The depressor response to AA (200 μg/kg) was significantly reduced in progesterone treated animals when compared to estrogen treated and control groups (P < 0.05). Similarly, testosterone treatment reduced the response to ia administration of AA (200 μg/kg) when compared to estrogen treatment. Similar effects were observed using PGE₂. No significant differences in pressor responses to PGF_2α were observed following gonadal hormone treatment. In all treatment groups the ia/iv dose response ratio to AA was unaltered, which implies that a single dose of gonadal hormone does not modify pulmonary AA metabolism.