Irbesartan

Irbesartan competes with angiotensin II (AII) for binding at the AT1 receptor subtype and antagonizes AII-induced contraction in rabbit aorta ring with IC50 of 4 nM. Irbesartan has no affinity for AT2 receptors. ^[1] Irbesartan (10 μM) blocks angiotensin II induced increase in α_v, β₁, β₃, and β₅ integrins, osteopontin, and α-actinin mRNA and protein levels in rat cardiac fibroblasts, leading to the decrease of cell attachment to extracellular matrix (ECM) proteins. ^[2] Irbesartan treatment markedly induces the expression of the adipogenic marker gene adipose protein 2 (aP2) in 3T3-L1 cells in a concentration-dependent manner with EC50 of 3.5 μM and 3.3-fold induction at the concentration of 10 μM. Irbesartan (10 μM) markedly induces transcriptional activity of the peroxisome proliferator–activated receptor-γ (PPARγ) by 3.4-fold independent of its AT1 receptor blocking action. ^[3] Pretreatment with Irbesartan (~10 μM) decreases angiotensin II-induced apoptosis in rat vascular smooth muscle cells by blocking angiotensin II internalization in a concentrationdependent manner. ^[4]

Oral administration of Irbesartan (1 mg/kg) reduces angiotensin II (AII)-induced hypertension, equipotent with losartan in conscious normotensive rats, markedly more active than losartan (10 mg/kg) in normotensive cynomolgus monkeys. ^[1] Administration of Irbesartan (7 mg/kg/day) significantly prevents skeletal muscle apoptosis and muscle atrophy in rats with monocrotaline-induced congestive heart failure (CHF), which is involved with the decrease of TNFα level and attributed to AT1 receptor blocking. ^[5]