Cardiac Hypertrophy in Spontaneously Hypertensive Rats
Masakazu IKEDA, Hitoshi TANIJIRI, Chujiro KASHII, Tadasu TAKATSU
1974
Japanese Heart Journal
In the previous studies, presented at the 7th and 8th annual meetings, ultrastructural changes in the myocardial cells of SHR at the age of 2 weeks to 1 year were observed chronologically by electron microscope. This report is to confirm the results by increasing the number of experimental animals. SHR (F19-21) at the age of 3, 5, 7, 9, 11, 13, 15, 17, 19, 21 weeks and 1 year were used comparing with the controls (Wistar Kyoto) of the corresponding age. The method used was the same as that in
more »
... evious study. The ratio of the area of mitochondria or myofibrils to the whole cross sectional area of myocardial cell was calculated and expressed by percentage. In controls, the area occupied by myofibrils was about 50% of the myocardial cell and was not changed throughout the experimental period, while that of mitochondria was about 40% at the age of 3 weeks followed by gradual decline to about 30% at the age of 1 year. In SHR, the area occupied by miofibrils was about 40% at the age of 3 weeks and was around 50% from 5th to 17th week after birth followed by a rapid fall to less than 40% at the age of 19 weeks and remained low until 1 year. The area of mitochondria was about 40% at the age of 3 weeks followed by a decline to less than 30% until 9th week, after which it increased to over 60% at the age of 1 year. Considering that the diameter of the myocardial cell increased throughout the investigation, the product of each percentage above mentioned multiplied by the square of the diameter was used as a parameter for comparing the absolute changes of mitochondria and myofibrils, since the cross sectional area of a cell is proportional to the square of the diameter. By this parameter the value of myofibrils in controls gradually increased, while that of mitochondria was not changed after the age of 7 weeks to 1 year. In SHR, the value of myofibrils increased up to 15th week followed by slight decrease after 19th week to 1 year, whereas that of mitochondria steadily increased from the age of 3 weeks to 1 year. With respect to the ultrastructure of myofibrils, no significant differences between both groups were found until 17th week after birth, when myofibrils
doi:10.1536/ihj.15.203
fatcat:3phrzyv5ujfczgaopiqkcnpfki