The effect of lumen conditions on oxygen uptake in perfused omasal laminae

Abstract

1. The vascular anatomy of the bovine omasal lamina permitted perfusion of a discrete area of the tissue. As occurs in vivo, oxygen was provided through the vascular system, while the luminal sides of the tissue could be kept in an anaerobic environment, thus allowing study of foregut tissue metabolism under physiologically realistic conditions.2. O2consumption of perfused leaves in the presence of anaerobic buffer was 64.9 and 73.5 nmol O2/mg dry weight per h in Expts 1 and 2 respectively, and was elevated (P< 0.05) when the lumen side of the tissue was exposed to an atmosphere of nitrogen gas.3. In Expt 1, the rate of O2consumption was increased (P< 0.01) by 35% as a result of suspension of a boiled preparation of rumen micro-organisms and particles (< 1 mm) in the anaerobic lumen buffer. Replacement of the boiled preparation with an unboiled suspension increased O2consumption further by 11 %, but this was not statistically significant (P> 0.05).4. In Expt 2, sequential addition of the following substrates or preparations to the lumen chambers all resulted in stepwise increases (P< 0.05) in O2consumption; 8 mM-butyrate, boiled rumen micro-organisms and particles and, finally, unboiled rumen micro-organisms and particles.5. Identities of the heat-labile and heat-stable components of the microbial and particle suspensions that caused enhancement of O2removal across the perfused tissue are discussed.