Invited Symposium: Hypertension II: Hypertension and Vascular Control
Tea, B.-S. (Research Center, University of Montreal Hospital (CHUM), Montreal, Canada)
Hamet, P. (Research Center, University of Montreal Hospital (CHUM), Montreal, Canada)
This study examined the response of both cell growth and apoptosis in the heart and aorta of spontaneoulsy hypertensive rats during beta-adrenergic blockadde therapy. Rats were treated or not with propranolol (50 mg/kg/day) for 2 or 4 weeks starting at 10-11 week of age. DNA synthesis was measured by [3H]-thymidine incorporation in vivo. Apoptosis was quantified by radiolabeling of 3'-OH ends in the extracted DNA with terminal deoxynucleotidyl transferase, followed by gel electrophoresis and quantification by PhosphoImager of radioactivity in oligonucleeosomal DNA fragments.After 4 weeks of treatment, although propranolol did not decrease systolic blood pressure significantly, the heart rate was lowered by 20% (vs control: 360+17 beats per minute). In the aorta, propranolol failed to affect vascular growth and apoptosis. In contrast, in the heart we observed that a 4-week treatment caused a significant 3- to 4-fold in apoptosis (vs control: 0.4+0.1 arbitrary units/ ug DNA; P < 0.05) and a regression of hypertrophy as measured by the heart to body weight ratio (by 11% vs control: 5.2+0.1 x 10E-3). These effects were preceded by a transient reduction in DNA synthesis (by 17% vs control: 831+31 cpm/100ug DNA; P < 0.05) at 2 weeks of therapy. Taken together, these results suggest that beta-blockade stimulate apoptosis (1) in an organ-specific manner, i.e. in the heart but not the aorta at 4 weeks of therapy, and (2) independently of blood pressure reduction. Supported by MRCC and FRSQ.
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|deBlois, D.; Tea, B.-S.; Hamet, P.; (1998). Selective Induction of Apoptosis in the Heart but Not the Aorta During Beta-adrenergic Blockade in the SHR. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/boegehold/deblois0801/index.html|
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