Pimobendan improves right ventricular myocardial contraction and attenuates pulmonary arterial hypertension in rats with monocrotaline-induced pulmonary arterial hypertension.
OBJECTIVE
The present study aimed to evaluate the therapeutic effect of pimobendan treatment for pulmonary hypertension (PH) in rats administered monocrotaline (MCT).


METHODS
Fifty-four 12-week-old male Sprague-Dawley rats were injected with monocrotaline or saline solution. Serial echocardiography and right ventricular systolic pressure (RVSP) measurement via a cardiac catheter were performed. After injection of MCT, rats received oral pimobendan (MCT/pimobendan group) or no treatment (MCT group) until undergoing echocardiography and cardiac catheter insertion.


RESULTS
Right ventricular systolic pressure in the MCT/pimobendan group was lower than that in the MCT group at 6 weeks. Right ventricle free wall (RVFW) myocardial systolic velocity (Sm) in the MCT group showed a reduction compared with the saline group at 2 weeks. RVFW Sm in the MCT/pimobendan group was preserved as compared with the saline group at 2 weeks. RVFW Tei index in the MCT/pimobendan group showed a reduction compared with the saline group and the MCT group at 2 weeks. Echocardiography in the MCT/pimobendan group showed improvement compared with MCT rats.


CONCLUSIONS
Both a reduction in RVSP and improvement in myocardial contraction were demonstrated with administration of pimobendan in rats with PH induced by MCT. Echocardiography evaluation of systolic function seems to be useful for monitoring excess administration of pimobendan.
Department of Veterinary Surgery, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
Rieko
R
Yoshiyuki
Department of Veterinary Surgery, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
Telma Mary
TM
Nakata
Department of Veterinary Surgery, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
Toshiharu
T
Fukayama
Department of Veterinary Surgery, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
Lina
L
Hamabe
Department of Veterinary Surgery, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
Hsu
H
Huai-Che
Department of Veterinary Surgery, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
Shuji
S
Suzuki
Department of Veterinary Clinical Oncology, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
Noboru
N
Machida
Department of Veterinary Surgery, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan.
Ryuji
R
Fukushima
Department of Veterinary Surgery, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan. ryo@vet.ne.jp.
Ryou
R
Tanaka
Monocrotaline; Pimobendan; Pulmonary hypertension; Rat; Right ventricular hypertrophy