Mesenteric preparations for quantitative microcirculatory studies

Abstract

Methods and technical aids for preparing frog and cat mesentery for observation under the microscope are described. The exposed frog mesentery has several advantages over other preparations. In particular, it is simple to prepare, requires minimum handling, and functions normally at room temperature. It may therefore be easily maintained, and the investigator may be fairly certain that the tissue is close to the “normal” physiological state during an experiment. The frog mesentery is also very transparent so that microvessels are clearly visible. Furthermore, frog microvascular components are significantly larger than comparable mammalian vessel components so quantitative measurements are more accurate. Disadvantages of the exposed frog mesentery are: (1) Total blood flow through an exposed segment is difficult to measure. (2) Nerve stimulation is not easy. (3) Large artery and vein pressures are not easily controlled or adjusted experimentally. The isolated, autoperfused cat mesentery circumvents some of the problems encountered with the frog preparation. Large artery and vein pressures are easily controlled. Substances may be introduced by infusion. Total blood flow through the isolated mesentery can be measured and controlled by simple means and the nerve supply is fairly easy to locate. The major disadvantage of the isolated, autoperfused cat mesentery is that it requires several hours to prepare. It is therefore difficult to establish objective criteria to judge whether the tissue is “normal” after the long delay between initial exposure and the start of data collection.