Splenic contraction-induced increases in arterial O2 reduce requirement for CBF in conscious dogs

N. Sato, Y. T. Shen, K. Kiuchi, R. P. Shannon, S. F. Vatner

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34 Scopus citations

Abstract

We investigated the extent to which sympathomimetic amines induced splenic contraction and associated increases in arterial O2 content (CaO2) and how these mechanisms affected control of the coronary circulation by sympathomimetic amines in conscious dogs. Blood hemoglobin (Hb) and CaO2 increased by 16 ± 2 and 18 ± 2%, respectively, during norepinephrine (NE, 0.8 μg · kg-1 · min-1 iv) in the intact, conscious state after splenic contraction. Phenylephrine (PE) induced similar effects. After either α1- adrenergic-receptor blockade or splenectomy, these effects were abolished. Isoproterenol (Iso) also decreased splenic thickness, which was abolished after ganglionic, α-, or β12-adrenergic-receptor blockade. Direct infusions of NE and PE into the splenic artery decreased splenic thickness and increased Hb and CaO2, whereas Iso had no effect. After splenectomy, NE did not increase CaO2, but coronary blood flow (CBF) increased more (73 ± 6%) vs. before splenectomy (49 ± 7%) without any differences before and after splenectomy in the responses of pressures, contractility, and myocardial O2 consumption (MV̇O2). In contrast, renal, mesenteric, and iliac artery blood flows were not significantly different in response to sympathomimetic amines before and after splenectomy. These data indicate that sympathomimetic amines induced splenic contraction either directly or reflexly via α-adrenergic-receptor stimulation. The consequent increase in Hb and CaO2 allows for equivalent increases in MV̇O2, but at a smaller increase in CBF.

Original languageEnglish (US)
Pages (from-to)H491-H503
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume269
Issue number2 38-2
DOIs
StatePublished - 1995
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

Keywords

  • arterial blood gas
  • catecholamine
  • coronary circulation
  • α-adrenergic receptors

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