Studies on the intracellular distribution of myocardial catecholamines of normal animals
Accumulated evidence indicates that the catecholamines are stored as granule
within the celles of adrenal medulla or sympathetic nervous tissues. Myocardial
catecholmines have been shown to be present in the particulate fraction as well as
in the soluble fraction obtained by differential centrifugation of cell free
suspension from homogenates of cardiac muscle (Potter and Axelrod, 1962; Wegman and
Kako, 1962; Campos Shideman, 1962). Howere, according to these investigatore the
ratio to that in the soluble fraction of myocardium varies considerably. This may
be attributed to a species and fraction procedure difference.
Present experiment was designed to determine the intracellular distribution of
myocardial catecholamines, with special reference to the animal species.
The heart was rapidly removed from animals under ether anesthesia and 5 volumes
of 0.38 M ice-cold sucose in a waring blender. The resultant suspension was passed
through a double layer of gauze to remove the fibrous tissue. The homogenate was
then centrifuged at 3-5℃ for 10 minutes at 600 xg (low-speed centrifugation),
which brought down incompletely fragmented cells and nucli. A low-speed supernatant
was thus obtained, and was again centrifuged at 3-5℃ for 30 minutes at 15,000 xg
(high-speed centrifugation), which fractionated into supernatant and sediment. The
concentration of catecholamines in each fraction obtained by the above differential
centrifugation, was determined spectrophotofluormetrically by the modified
procedure of the method described by Shore and Olin (1958).
1. Examination of the intracellular distribution of the myocardial catecholamines
of normal rabbits showed that a higher concentration of the aminos was present in
the high-speed supernatant fraction (0.40ug/gm) and the ratio of
supernatant/sediment was 4. The catecholamines present in the low-speed supernatant
was almost completely recovered in both fractions obtained by high-speed
2. In the cardiac homogenate of normal cats, a similar intracellular distribution
of catecholamines was observed. Thus, the concentrations of amines in high-speed
supernatant and sediment were 0.48 and 0.09ug/gm respectively.
3.In the experiment with cardiac homogenate of normal rate, it was also found
that higher concentration of catecholamines was present in the high-speed
supernatant and the ratio of supernatant/sediment was 4.3 which was not
significantly different from those observed in the cardiac homogenates of normal
rabbits or cats.
The concentrations of catecholamines in the high-speed supernatant and sediment
fractions would not represent the actual distribution in vivo. However, these
values are reproducible and relatively constant under the described experimental
conditions. Therefore, these may be considered useful as a criteria for the study
of intracellular distribution of myocardial catecholamines. From the above results,
it may be concluded that there is no significant difference in the intracellular
distribution of myocardial catecholamines of normal rabbits, cats and rats.