Vascular compliance and mean circulatory filling pressure in trout: Effects of ACE inhibition

Y. Zhang, E. Jenkinson, K. R. Olson

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26 Scopus citations

Abstract

Mean circulatory filling pressure (MCFP), whole body vascular compliance (C), and unstressed blood volume (USV) are important indexes of cardiovascular function in mammals, but they have not been measured in fish. In the present experiments, dorsal aortic (P(DA)) and sinus venosus (P(SV)) pressures were measured in unanesthetized trout before and during electrical cardiac fibrillation, while blood volume (BV) was manipulated between 50 and 150% of normal. Measurements were repeated after angiotensin-converting enzyme (ACE) inhibition with lisinopril. Cardiac fibrillation (zero-flow condition) rapidly (~5 s) dropped P(DA) and increased P(SV) (equals MCFP). MCFP in normovolemic trout (4.8 ± 0.3 mmHg) varied directly with BV. C determined from in vivo capacitance curves was similar to that obtained gravimetrically, in vitro (3.4 and 3.5 ml · mmHg-1 · kg body wt-1, respectively). USV was 13.3 ml/kg body wt (~45% of BV). ACE inhibition reduced P(DA) in unfibrillated trout at all BV and reduced P(DA) in fibrillated fish at BV ≥ 80%. ACE inhibition did not affect P(SV), MCFP, C, or USV. The systemic arteriovenous pressure gradient at zero flow (ΔPF0) was greatest at 100% BV (8.2 ± 0.5 mmHg) and was reduced by ACE inhibition at 80-120% BV. These results show that key indexes of venous function are readily measured in fish and that the trout venous system is not an effector of angiotensin-mediated regulation of arterial blood pressure. Thus angiotensin acts solely on arterial resistance vessels. Furthermore, the drop in ΔPF0 during ACE inhibition is due to a decrease in arteriolar resistance.

Original languageEnglish (US)
Pages (from-to)H1814-H1820
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume268
Issue number5 37-5
StatePublished - Jan 1 1995

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Keywords

  • blood pressure
  • cardiovascular
  • fish
  • renin angiotensin system
  • vein

ASJC Scopus subject areas

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

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