MICROVASCULAR DIMENSIONS AND GAS EXCHANGE

微血管尺寸和血管壁之间的精确关系 气体交换器官的扩散特性不佳 明白 这在很大程度上是由于难以使 直接、同时测量气体交换和血管 肺部的尺寸。 然而，这种测量可以容易地 在不同的呼吸器官、两栖动物皮肤上制成。 这 格兰特建议评估一些气体交换的基本原则， 通过直接测量两栖动物的皮肤来确定 膜对一氧化碳的扩散能力（DMCO） 受毛细血管直径变化的影响， 灌注毛细血管，血液-空气扩散的厚度 屏障 一种使用所有体内测量的新方法将是 进行测定DMCO和气体吸收能力， 红细胞在毛细血管中流动。 这些 这些决定将检验以下假设：1）变化 仅毛细管直径对DMCO没有影响，2）变化 在灌注毛细血管的密度有较大的影响， DMCO在低毛细管密度比在较高的毛细管密度。 3)随着血液-空气扩散屏障的厚度增加， 灌注毛细血管密度的变化对 DMCO 扩散能力在调节中的作用 还将评估两栖动物皮肤中的O2和CO2交换。 最后，将使用已知的数学模型来开发数学模型。 描述扩散气体通量的管道热通量关系 在两栖动物的皮肤上 实验将在有髓无尾两栖动物上进行。 的 C 0、C 02和02的净通量将在一个小的 用质谱法检测了一小块皮肤 DMCO和皮肤电导 02和CO2的浓度。 与这些通量同时 测量，毛细管直径和毛细管密度， 将通过视频显微镜确定皮肤的相同区域。 局部应用将引起毛细血管密度的变化 苯乙醯胺 毛细血管直径将改变 使用泵灌注的皮肤制剂， 压力可以调节。 血气的浓度 扩散屏障将使用标准组织学方法测量 技术. 不同的两栖动物有不同的表皮 厚度将被测试和比较。 对两栖动物皮肤的研究将提供独特的 有助于了解基本问题的信息 哺乳动物的气体交换， 因为哺乳动物肺部的复杂性。

Precise relationships between microvascular dimensions and the diffusion characteristics of gas exchange organs are not well understood. This is due, in large part, to difficulties in making direct, simultaneous measurements of gas exchange and vascular dimensions in the lung. Such measurements, however, can readily be made on a different respiratory organ, amphibian skin. This grant proposes to evaluate some basic principles of gas exchange by making direct measurements on amphibian skin to determine how the membrane diffusing capacity to carbon monoxide (DMCO) is affected by changes in capillary diameter, the density of perfused capillaries, the thickness of the blood-air diffusion barrier. A new method using all in vivo measurements will be performed to determine DMCO and the gas uptake capacity of erythrocytes while they flow through capillaries. These determinations will test the following hypotheses: 1) Changes solely in capillary diameter have no affect on DMCO, 2) Changes in the density of perfused capillaries have a larger effect on DMCO at low capillary density than at higher capillary densities. 3) As the thickness of the blood-air diffusion barrier increases, changes in the density of perfused capillaries have less effect on DMCO. The role of diffusing capacity changes in the regulation of 02 and C02 exchange in amphibian skin will also be evaluated. Finally, a mathematical model will be developed using known relationships of heat flux from pipes to describe diffusive gas flux across amphibian skin. Experiments will be performed on pithed anuran amphibians. The net fluxes of C0, C02 and 02 will be measured across a small patch of skin by mass spectrometry. DMCO and skin conductance to 02 and C02 will be determined. Simultaneous with these flux measurements, capillary diameter and capillary density in the same region of skin will be determined by video microscopy. Changes in capillary density will be elicited by topical application of phenylephrine to the skin. Capillary diameters will be altered using a pump-perfused skin preparation in which intravascular pressure can be modulated. The thickness of the blood-air diffusion barrier will be measured using standard histological techniques. Different amphibians with a variety of epidermal thickness will be tested and compared. This investigation of amphibian skin will provide unique information helpful to the understanding of basic issues in mammalian gas exchange that have not been experimentally accessible because of the complexity of the mammalian lung.