Role of Ca(2+) and vitamin D in the prevention and treatment of osteoporosis.

Osteoporosis is defined as a progressive systemic skeletal disease characterised by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. The clinical relevance of osteoporosis derives from the fractures that it produces. More than one-third of the adult women will suffer one or more osteoporotic fractures in their lifetime.

Oxidative stress induced by tert-butyl hydroperoxide causes vasoconstriction in the aorta from hypertensive and aged rats: role of cyclooxygenase-2 isoform.

We analyzed the mechanisms involved in the effect of tert-butyl hydroperoxide (t-BOOH) in isolated aortic rings with and without endothelium from normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) at 6, 18, and 24 months of age. t-BOOH (1 microM-10 mM) induced concentration-dependent contractions that were scarcely modified by aging and potentiated in SHR and by endothelium removal. The nitric oxide synthase and prostacyclin synthase inhibitors N(G)-nitro-L-arginine methyl ester (100 microM) and tranylcypromine (100 microM), respectively, increased both basal tone and the t-BOOH-induced contractions in intact segments from WKY, with these effects not observed in SHR.

Changes in plasma oxidative state with age and their influence on contractions elicited by noradrenaline in the rat tail artery.

The present study analyzes the changes in plasma oxidative state with age and their influence on the contractions induced by noradrenaline (NA) in endothelium-denuded segments from the tail artery of 6- (young), 24- (old) and 30- (very old) month-old Sprague Dawley rats. The sensitivity (-log EC50) to NA increased with age, this increase being higher in old than in very old animals. Moreover, the maximum response (Emax) to NA did not change in old rats, whereas decreased in very old animals.

Mechanisms involved in the cellular calcium homeostasis in vascular smooth muscle: calcium pumps.

The regulation of cytosolic Ca2+ homeostasis is essential for cells, and particularly for vascular smooth muscle cells. In this regulation, there is a participation of different factors and mechanisms situated at different levels in the cell, among them Ca2+ pumps play an important role. Thus, Ca2+ pump, to extrude Ca2+; Na+/Ca2+ exchanger; and different Ca2+ channels for Ca2+ entry are placed in the plasma membrane.

Contractile responses elicited by hydrogen peroxide in aorta from normotensive and hypertensive rats. Endothelial modulation and mechanism involved.

The present study analyses the influence of hypertension and endothelium on the effect induced by hydrogen peroxide (H2O2) on basal tone in aortic segments from normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) of 6-month-old, as well as the possible mechanisms involved. Single (1 mM) or cumulative (100 nM-10 mM) concentrations of H2O2 produced a transient contraction or a concentration-dependent increase of basal tone, respectively, in segments from WKY and SHR. In both cases, the contractions were higher in intact segments from hypertensive than from normotensive rats, and increased by endothelium removal in both strains.