Faculty Collaboration Database

Whole body autoregulation in conscious areflexic rats during hypoxia and hyperoxia. Am J Physiol 1989 Apr;256(4 Pt 2):H1023-9

Date

04/11/1989

Pubmed ID

2705545

DOI

10.1152/ajpheart.1989.256.4.H1023

Scopus ID

2-s2.0-0024567010 (requires institutional sign-in at Scopus site)   8 Citations

Abstract

We have previously shown whole body autoregulation during normoxia in conscious areflexic rats in response to an acute increase and decrease in blood volume. In this study we used this technique to determine the effect of hypoxia and hyperoxia on whole body autoregulation. Rats with an arterial catheter for blood pressure measurement and an electromagnetic flow probe for cardiac output measurement were placed in a chamber with a controlled oxygen environment. Neurohumoral blockade was achieved with chlorisondamine (10 mg/kg), methscopolamine (0.5 mg/kg), captopril (1 mg/kg), and [d(CH2)5Tyr(Me)]arginine vasopressin (10 micrograms/kg). Hemodynamic variables were restored to normal with a constant norepinephrine infusion. Group 1 (n = 7) underwent a 6-min infusion of donor blood (0.9 ml) during hypoxia (Po2 = 52 +/- 3 mmHg) and hyperoxia (Po2 = 296 +/- 12 mmHg). Group 2 (n = 8) was subjected to a 6-min withdrawal of blood (0.9 ml) during hypoxia (72 +/- 2 mmHg) and hyperoxia Po2 = 258 +/- 8 mmHg). The slope of the pressure-flow relationship was used as an index of autoregulation so that a slope of 0 indicated complete autoregulation and a slope of 1 represented no autoregulation. The pressure-flow slopes with volume expansion were 0.54 during hypoxia and 0.15 during hyperoxia, while the slopes with volume contraction were 0.29 during hypoxia and 0.54 during hyperoxia. Thus, when arterial pressure was raised above normal, the autoregulatory capacity was greater during hyperoxia than with hypoxia. Conversely, when arterial pressure was lowered below normal, the autoregulatory capacity was greater during hypoxia than with hyperoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Author List

Hinojosa-Laborde C, Greene AS, Cowley AW Jr

Author

Allen W. Cowley Jr PhD Professor in the Physiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Blood Volume
Hemodynamics
Homeostasis
Hypoxia
Male
Oxygen
Rats
Rats, Inbred Strains
Reflex, Abnormal
Time Factors