Effects of norepinephrine and sympathetic stimulation on intestinal oxygen extraction

A. P. Shepherd, D. Mailman, T. F. Burks, E. D. Jacobson

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Abstract

Previous studies have shown that stimulation of the sympathetic nerves may constrict precapillary sphincters and thereby reduce the density of the perfused intestinal capillary bed. A computer model of the intestinal circulation (Physiologist 15:264, 1972) predicted that the diffusion parameters altered by precapillary sphincter closure (e.g. capillary surface area and mean capillary to cell diffusion distance) would be sufficient to affect intestinal O2 extraction. To test this prediction in an animal model, the authors made continuous measurements of arteriovenous oxygen difference (A-V ΔO2) and perfusion pressure during constant flow perfusion of isolated loops of canine small bowel. Intra arterial infusion of norepinephrine (NE) or stimulation of peri arterial nerves (SS) for a 7 min period produced sustained increases in vascular resistance (R) and sustained reductions in A-V ΔO2. Maximal changes in R and A-V ΔO2 occurred by the 2nd min of NE or SS, and subsequently both parameters 'escaped' somewhat. The maximal and steady state values of these parameters were dose or frequency dependent. In other experiments, SS caused synchronous decreases in A-V ΔO2 and Rb86 extraction. The extractions of Rb and O2 were significantly correlated. These results support the view that NE and SS cause sustained reductions in the density of the perfused capillary bed which are sufficient to reduce intestinal extraction of Rb and O2 despite constant flow perfusion.

Original languageEnglish (US)
Pages (from-to)608
Number of pages1
JournalFederation Proceedings
Volume32
Issue number3 (I)
StatePublished - 1973
Externally publishedYes

ASJC Scopus subject areas

  • Medicine(all)

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