An Isolated Perfused Frog Skin Preparation for the Study of Gas Exchange

Abstract

The vascular arrangement of frog skin offers two advantages for studying gas exchange within the microcirculation, both due to the relatively simple two-dimensional geometry of the skin: 1) all vessels are visible, thus amenable to techniques being developed for analysing blood flow from video images, and 2) oxygen uptake, gas partial pressure gradients, perfusion rate, perfusate capacitance etc. can be easily manipulated. Other tissues have much more complex three dimensional vasculatures in which it is difficult to observe an entire capillary bed supplied by a particular vessel. Tissues that are thin enough to observe red cell flow through the entire capillary bed (mesentery, thin muscles) have too low an oxygen consumption to simultaneously measure oxygen delivery. Thus, it is difficult to test models of oxygen delivery being developed to predict the effects of microcirculatory red cell flow patterns on gas exchange. Although the isolated perfused frog skin preparation was developed specifically for studying cutaneous oxygen uptake, it has promise for studying more general features of gas exchange in capillary beds, such as the effects of blood flow heterogeneity and red cell spacing on oxygen uptake and delivery.