Age is a risk factor for maladaptive changes in rats exposed to increased pressure loading of the right ventricular myocardium.
OBJECTIVE
To study the adaptive potential of the right ventricular myocardium after 30 days of mechanical-induced overload in rats from two different age groups.


METHODS
We banded the pulmonary trunk, so as to increase the systolic work load of the right ventricle, in 19 adult Sprague-Dawley rats at the age of 10 weeks, and 16 weanlings when they were 3 weeks-old, using 10 adults and 10 weanlings as controls. We analysed the functional adaptation and structural changes of the right ventricular myocardium, blood vessels and interstitial tissue after 30 days of increased afterload.


RESULTS
The increased workload induced an increase of the right ventricular weight and free wall thickness in animals from both age groups when compared to controls. These changes were mostly related to cardiomyocytic hypertrophy, as confirmed by the expression of myocardial hypertrophic markers, without any apparent increase of their number, a "reactive" fibrosis especially evident in the adult rats, with p-value less than 0.0001, and a more extensive neocapillary network in the weanlings compared to the adults aubsequent to banding, the p-value being less than 0.0001.


CONCLUSIONS
In response to right ventricular afterload, weanlings showed a higher adaptive capillary growth, which hampered the development of fibrosis as seen in the adult rats. Age seems to be a risk factor for adverse structural-functional changes of right ventricle subjected to increased workload.
Vida
Vladimiro L
VL
Department of Pediatric Cardiac Surgery, University of Padua, Padua, Italy. vladimirovida@interfree.it
Angelini
Annalisa
A
Ausoni
Simonetta
S
Bilardi
Alessandra
A
Ori
Carlo
C
Vlassich
Francesca
F
Zoso
Valentina
V
Milanesi
Ornella
O
Sartore
Saverio
S
della Barbera
Mila
M
Zaglia
Tania
T
Thiene
Gaetano
G
Stellin
Giovanni
G
D000367:Age Factors; D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D004452:Echocardiography; D005500:Follow-Up Studies; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology*; D017380:Hypertrophy, Right Ventricular / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism / Q000473:pathology*; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012307:Risk Factors; D016278:Ventricular Function, Right / Q000502:physiology*; D017725:Ventricular Pressure / Q000502:physiology*
D009124:Muscle Proteins