High Salt Upregulates Ca-Sensing Receptor Expression and Ca-Induced Relaxation of Contracted Mesenteric Arteries from Dahl Salt-Sensitive Rats.

High Ca lowers blood pressure in hypertension, but the mechanism is not clear. The missing link may be the perivascular sensory nerve Ca-sensing receptor (CaSR) that mediates a vasodilator system after activation by interstitial Ca Our results show that high salt increased CaSR expression in mesenteric arteries as well as Ca relaxation of contracted mesenteric arteries from salt-sensitive (SS) rats. The CaSR was expressed as a doublet (≈120-150 kDa) in arteries from animals fed a high-salt diet for 1-4 weeks.

Nitric-oxide synthase knockout modulates Ca²⁺-sensing receptor expression and signaling in mouse mesenteric arteries.

Extracellular calcium (Ca²⁺(e))-induced relaxation of isolated, phenylephrine (PE)-contracted mesenteric arteries is dependent on an intact perivascular sensory nerve network that expresses the Ca²⁺-sensing receptor (CaSR). Activation of the receptor stimulates an endocannabinoid vasodilator pathway, which is dependent on cytochrome P450 and phospholipase A₂ but largely independent of the endothelium. In the present study, we determined the role of nitric oxide (NO) in perivascular nerve CaSR-mediated relaxation of PE-contracted mesenteric resistance arteries isolated from mice.

Mesenteric artery contraction and relaxation studies using automated wire myography.

Proximal resistance vessels, such as the mesenteric arteries, contribute substantially to the peripheral resistance. These small vessels of between 100-400 μm in diameter function primarily in directing blood flow to various organs according to the overall requirements of the body. The rat mesenteric artery has a diameter greater than 100 μm.

Action of thiazide on renal interstitial calcium.

Background: Although thiazides increase urinary sodium excretion, they also decrease urinary calcium excretion. Recent studies in our laboratory have shown that increased dietary salt significantly reduces interstitial fluid calcium in Dahl salt-sensitive (DS) rats, and this was associated with a rise in blood pressure and increased urinary calcium excretion. Owing to the vasorelaxant actions of increased extracellular fluid calcium, we reasoned that the antihypertensive action of hydrochlorothiazide (HCTZ), a commonly used thiazide, may be the result of increased interstitial fluid calcium as a consequence of decreased urinary calcium excretion.