Die Rolle der Ca2+-aktivierten K+-Kanäle KCa3.1 und KCa2.3 bei retinalen Angiogeneseprozessen

Angiogenesis plays an important role in many physiological and pathological processes. It is well known that the stimulation for vessel growth is controlled by ion channels in the endothelial cell membrane. Recent results suggest that the two calcium dependant potassium channels KCa3.1 and KCa2.3 are also important for angiogenesis. In this dissertation I investigated whether a change of expression in terms of knockout or upregulation affect the morphological and quantitative vascularisation of the retina. Analysis took place in young, 5- and 7-days old mice and in adult, 30-days old mice in different types of transgenic animals. It was possible to either specifically knockout one of the two channels, overexpress KCa2.3 or to combine knockout and overexpression. For the evaluation it was necessary to use and refine existing and to develop new methods for the preparation and visualisation of the retinal vessels. A very reliable and homogeneous immuno-histochemical staining of the vessels was reached by combining two antibodies. The first one was a type IV Kollagen antibody and the second one, coupled with alexa fluor, was specific to the first one. The preparation was then used to produce a graph of the main retinal vessel plexus of the retina and to obtain a picture of the complete retina via technical-optical methods. The so obtained picture was analysed using different methods to qualitatively and quantitatively determine the morphological changes of the vessels. A grey scale analysis was used to determine which percentage of the total area was covered with vessels. Additionally, the branching of the vessels in certain areas was evaluated to obtain the density of the capillary plexus. Finally, the diameter of both small as well as large vessels was measured to examine whether there are differences between the animal models. It was possible to show that the knockout of the KCa3.1 channel coincides with a increase of vessels in the retina, and specifically with a significant increase of the vascular branching. Similarly, the knockout of the KCa2.3 channel effects proangiotic changes in the retina, also causing an increase in the branching. Furthermore, the knockout of both channels increases the vascular branching as compared to the knockout of only one channel. However, the diameter of the capillars is not changed in any group of animal models. For the very young, five and seven day old, animals the results are less obvious and there are no clear differences between the different animal models, even though tendencies similar to the adult mice are discernible. Additionally, the used animal models allowed for investigation of the effects of overexpression of the KCa2.3 channel on the vascularisation of the retina. KCa2.3T/T transgenic animals and double transgenic animals KCa3.1-/-/ KCa2.3T/T with an overexpression of KCa2.3 showed a vessel density compared to the Wildtypes. The dependence of the KCa3.1 and KCa2.3 channels for angiogenetic effects have been shown in this dissertation. It is possible that these channels could be a useful target for pharmacological manipulation of neovascularisation and vessel growth.