In-vivo- und In-vitro-Untersuchungen zur myokardialen Kontraktilität vergleichend an Weißen-Neuseeland-Kaninchen und Chinchilla-Bastard-Kaninchen

Laboratory rabbits are frequently used in animal experimental
research. The aim of the present study is to compare the heart
functions of New Zealand White Rabbits (WN) to the one of
Chinchilla Bastard Rabbits (CB) in vivo and in vitro. The higher
stress susceptibility of New Zealand White Rabbits noticed in
clinical observations is to be examined based on parameters of
cardiac contractility. To determine the morphometric parameters and
the contractile function of the heart, six animals at a time
anaesthetized with Propofol are examined by means of
echocardiography. As a result the thickness of the heart wall and
the diameter of the left ventricle are determined, and the
fractional shortening is calculated. All parameters are measured at
the end of systole and diastole. In the next step single
cardiomyocytes of six additional animals from each race are
enzymaticly isolated from the removed hearts with a modified
Langendorff-Perfusion-Apparatus. The contractility of the single
cells is analysed under controlled conditions as well as under
ß-agonist stimulation with Isoprenalin concentrations of 10-11 to
10-6 M. In terms of the strength of the heart wall or the left
ventricle’s diameter, the ultrasound investigations don’t yield any
significant differences. However Chinchilla Bastard Rabbits show a
significantly higher fractional shortening (40,19 ± 3,19 %) than
New Zealand White Rabbits (35,49 ± 3,78 %). Regarding the single
cardiomyocytes a distinct difference in the duration of basal
shortening can be noticed. WN clearly show a longer shortening
period (255,80 ms) than CB (208,73 ms). Cardiomyocytes of WN
respond to very low Isoprenalin concentrations from 10-11 to 10-10
M with a significantly higher shortening speed. Broad differences
in the fractional shortening of the single cells arise during the
experiments with the highest concentration of Isoprenalin (10-6 M).
The fractional shortening of cardiomyocytes from WN amount to 7,47
%, whereas the cardiomyocytes from CB reach 9,89 %. On the single
cell level WN react more sensitively to the stimulation with
increasing Isoprenalin until a threshold of 10-8 M. Beyond that
level the contractility decreases visible. However on the organ
level the CB have basal a higher contractility. The breed specific
results found in this research study could be caused by differences
in sensitivity, regulation and the number of ß-receptors as well as
by differences in anaesthetic behaviour. Further investigations on
a biochemical and molecular level should be carried out to answer
these questions.