Oxygen Uptake and Tissue Oxygen Tension during Adrenergic Stimulation in Canine Subcutaneous Adipose Tissue

Abstract

The effect of sympathetic nerve stimulation (NS) and injected noradrenaline (NA) or isoprenaline (Iso) on PvO2 [venous O2 tension], .ovrhdot.VO2 and PtO2 [tissue O2 tension] was studied in isolated canine subcutaneous adipose tissue. These effects were compared to those produced by mechanical blood flow reduction (clamping). Resting .ovrhdot.VO2 measured 13.0 .+-. 2.3 .mu.mol .times. min-1 .times. 100 g-1. When blood flow was reduced by 20% or less there was no significant change of .ovrhdot.VO2. Reducing blood flow to 50% of control or less by NS caused a parallel reduction in .ovrhdot.VO2, while clamping reduced .ovrhdot.VO2 significantly less. NA gave effects similar to those of NS. After NS or NA there was a period of hyperemia and increased O2 extraction which more than compensated for the decrease in .ovrhdot.VO2 during vasoconstriction. Such a net increase in .ovrhdot.VO2 was not produced by clamping. Control PtO2 averaged 29 .+-. 12 mmHg. NA reduced it by 70% and clamping to the same blood flow level only by 14% (P < 0.01). A mere reduction in blood flow had little effect on PtO2, while blood flow reduction combined with redistribution of blood flow and an increased O2 demand can lead to tissue hypoxia.