Oxygen consumption in the avascular guinea pig retina.
Cringle, Stephen, Dao-Yi Yu, Valerie Alder, Er-Ning Su, and Paula Yu.
Lions Eye Institute, Centre for Ophthalmology and Visual Science,
University of Western Australia
APStracts 3:0129H, 1996.
Oxygen consumption across the retina of a mammal with a naturally
avascular retina has not previously been investigated. The oxygen
consumption across the holangiotic retina of the guinea pig was
measured in-vivo by spatial analysis of the intraretinal oxygen
profile. The avascular nature of the guinea pig retina allows the
inner retina to be included in the analysis without disrupting the
normal physiological state of the retina. Oxygen sensitive
microelectrodes (1mm tip) were used to make high resolution
measurements of oxygen tension through the retina of anesthetized,
mechanically ventilated guinea pigs (n=10). Oxygen profiles were then
analyzed in terms of oxygen tension as a function of distance from
the choriocapillaris/Bruch's membrane, and the data fitted to an
established mathematical model of retinal oxygen consumption. The
average oxygen consumption of the full thickness of the guinea pig
retina was 1.1 + 0.09 ml O2/(min.100g) (n=10). The average oxygen
consumption of the outer half of the retina was 2.07 + 0.17 ml
O2/(min.100g), whilst that of the inner half was only 0.12 + 0.04 ml
O2/(min.100g). A localised region of high oxygen consumption was
identified in the outer retina in every case, and this region
accounted for an average of 93.9 + 2.0 % of the total retinal oxygen
consumption. Only 5.2 + 1.4 % of the total oxygen consumption was
attributable to the inner half of the retina. When choroidal oxygen
tension was increased via a combination of systemic hyperoxia and
hypercapnia, high oxygen levels could be sustained in all retinal
layers. Under these conditions of an excess oxygen supply the inner
retina still consumed only 0.45 + 0.11 ml O2/(min.100g) which was
13.8 + 2.5 % of the total retinal oxygen consumed. The relatively low
oxygen consumption in the inner retina of the guinea pig may reflect
an interesting adaptation to the constraints imposed by the absence
of a retinal circulation in this species.
Received 7 February 1996; accepted in final form 18 March 1996.
APS Manuscript Number H121-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 April 96