The role of beta 2-adrenergic vascular receptors in the peripheral vasodilation caused by 17 beta-estradiol in anesthetized pigs.
It has been previously shown in anesthetized pigs that intravenous infusion of 2 microg/h of 17beta-estradiol primarily dilated renal, iliac and coronary circulations, while higher doses of the hormone were required to cause vasodilation also in the mesenteric vascular bed. In the same experimental model, a tonic beta2-adrenoceptor mediated vasodilation, which could be argued to attenuate the vasodilator effect of 17beta-estradiol, has been described. The present study was planned to investigate the role of beta2-adrenergic receptors in the hemodynamic responses of renal and mesenteric vascular beds to 17beta-estradiol. Changes in flow caused by intravenous infusion of 2 microg/h of the hormone at constant heart rate and aortic blood pressure in the left renal and superior mesenteric arteries were assessed using electromagnetic flowmeters. In six pigs, infusion of 17beta-estradiol caused an increase in renal blood flow, which averaged 12.1% of the control values, without affecting mesenteric blood flow. In the same pigs, after hemodynamic variables had returned to the baseline values, blockade of beta2-adrenergic receptors with butoxamine caused an increase in aortic blood pressure and an increase in renal and mesenteric resistance. The subsequent infusion of 17beta-estradiol elicited increases in renal and mesenteric blood flow which respectively averaged 19.6% and 12.8%. Therefore, the present study in anesthetized pigs have shown that the vasodilator responses of the renal and mesenteric circulations to 17beta-estradiol were attenuated and even masked by a tonic beta2-adrenoceptor mediated vasodilation. This indicates that some vasodilator effects elicited by normally used replacement doses of the hormone may not be apparent.
Molinari
C
C
Dipartimento di Scienze Mediche, Università del Piemonte Orientale A. Avogadro, Novara, Italy. molinari@med.no.unipmn.it
Battaglia
A
A
Grossini
E
E
Mary
D A
DA
Surico
N
N
Vacca
G
G
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000704:Analysis of Variance; D000758:Anesthesia; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002078:Butoxamine / Q000494:pharmacology; D002245:Carbon Dioxide / Q000097:blood; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007262:Infusions, Intravenous; D010100:Oxygen / Q000097:blood; D018343:Receptors, Adrenergic, beta-2 / Q000097:blood / Q000502:physiology*; D012079:Renal Circulation / Q000187:drug effects*; D013152:Splanchnic Circulation / Q000187:drug effects*; D013552:Swine; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology*
D000319:Adrenergic beta-Antagonists; D018343:Receptors, Adrenergic, beta-2; D002078:Butoxamine; D002245:Carbon Dioxide; D004958:Estradiol; D010100:Oxygen