saprisartan-potassium and Myocardial-Infarction

The objective of the study was to investigate the involvement of angiotensin II receptor subtypes 1 and 2 in total interstitial cell and endothelial cell DNA synthesis and cardiac function after myocardial infarction (MI) in the rat. Rats with a MI were treated with either AT1 receptor antagonist GR138950C (2 mg/kg/day) or the AT2 receptor antagonist PD123319 (3 mg/kg/day). Total interstitial cell (that is endothelial cells and fibroblast-like cells) DNA synthesis in the interventricular septum was significantly increased 2 weeks after MI. 33+/-3% of DNA synthesizing cells were identified as endothelial cells. PD123319, but not GR138950C significantly reduced total interstitial DNA synthesis. Both agents did not alter the fraction of DNA synthesizing endothelial cells. The effects on cardiac function were studied in parallel groups. MI reduced both cardiac output and stroke volume at 3 weeks after MI PD123319 reduced CO, whereas GR138950C did not affect cardiac function. Thus, the data show that AT2 receptor blockade, but not AT1 receptor blockade early after rat myocardial infarction inhibits interstitial DNA synthesis and decreases cardiac function.

Topics: Angiotensin Receptor Antagonists; Animals; Benzofurans; Cardiac Output; Cell Division; DNA; Endothelium; Fibroblasts; Imidazoles; Male; Myocardial Infarction; Myocardium; Pyridines; Rats; Rats, Wistar; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Stroke Volume

This study was undertaken to investigate changes in aortic geometry and compliance after long-term blockade of angiotensin receptors type 1 (AT1) and AT2 receptors under basal conditions and after myocardial infarction (MI). Sham-operated (sham) or MI rats received either no treatment, AT1 antagonist GR138950C (GR; 2 mg/kg/day i.v.), or AT2 antagonist PD123319 (PD; 3 mg/kg/day s.c.). After 3 weeks, mean arterial blood pressure (MAP) was measured. Thoracic aorta diastolic diameter (D[dia]), compliance coefficient (CC), and distensibility coefficient (DC) were determined noninvasively in anesthetized rats by using ultrasound and wall tracking. After the rats were killed, histologic measurements were made on aortic cross sections. In sham rats, MAP was reduced by GR treatment (76 +/- 6 vs. 106 +/- 5 mm Hg), but not by PD. D(dia) was reduced in both GR-treated (1.74 +/- 0.08 vs. 2.09 +/- 0.05 mm) and PD-treated (1.83 +/- 0.05 vs. 2.09 +/- 0.05 mm) sham rats. CC and DC were not modified by either treatment. Although media cross-sectional area was not affected by either GR or PD treatment in sham rats, media thickness and media/lumen ratio were increased in both cases. Induction of MI had no effect on aortic structure, geometry, or mechanics; however, treatment with either GR or PD improved DC versus untreated MI rats. We conclude that AT1 and AT2 receptors are involved in angiotensin II-mediated effects on aortic geometry and mechanics under both basal conditions and after MI. Whereas blockade of AT1 receptors most likely influences vascular properties through a depressor mechanism, AT2 receptors induce pressure-independent remodeling.

Topics: Angiotensin Receptor Antagonists; Animals; Antihypertensive Agents; Aorta, Thoracic; Benzofurans; Blood Pressure; Imidazoles; Injections, Intravenous; Injections, Subcutaneous; Male; Myocardial Infarction; Pyridines; Rats; Rats, Wistar; Ultrasonography