Effect of Antihypertensive Losartan on Ca2+ Mobilization in the Aorta of Middle-Aged Spontaneously Hypertensive Female Rats

Hypertension, a leading factor for cardiovascular diseases (CVD), is a particularly heavy burden in women during middle age, when cardioprotective hormones begin to decline. The abnormal handling of calcium (Ca²⁺) in vascular smooth muscle cells (VSMCs) leads to increased vasoconstriction, remodeling, and altered arterial compliance during hypertension. The Spontaneously Hypertensive Rats (SHR) is a model of essential hypertension, and middle-aged females with hypertension represent a stage of disease where vascular dysfunction is prominent but understudied. Losartan, a widely prescribed angiotensin II (AngII) receptor (AT1R) blocker, exerts antihypertensive effects by affecting Ang II/Ca²⁺ signaling. However, whether it corrects the Ca²⁺ mishandling in the aorta of middle-aged female SHR has not been established. In this study, the thoracic aorta from 36-week-old female SHRs treated with losartan was assessed for Ca²⁺ mishandling using myography and biochemical assays. Meanwhile, biomechanical properties and stiffness were evaluated using Pulse Wave Velocity (PWV), Atomic Force Microscopy (AFM), and assessments of collagen and elastin contents. Compared with normotensive controls, SHR demonstrated disrupted Ca²⁺ handling, increased stiffness, and Extracellular Matrix (ECM) remodeling in middle-aged females. Treatment with losartan abrogated Ca²⁺ mishandling influx and efflux in the VSMC, decreased stiffness, and restored the aortic structural changes. These findings demonstrate that losartan abolishes Ca²⁺ mishandling and highlight a mechanistic role of AT1R blockade in restoring vascular function in the aorta of middle-aged females during hypertension.