Estrogen-induced relaxation of the rat tail artery is attenuated in rats with pulmonary hypertension

Protective effect of nicotinamide and L-arginine against monocrotaline-induced pulmonary hypertension in rats: gender dependence

Background

The purpose of this paper was to examine the effects of nicotinamide (ND) and l-arginine (l-ARG) on pulmonary vascular and heart changes induced by pulmonary hypertension in rats in a gender-dependent way.

Methods

Experiments were performed on male (M) and female (F) rats. PAH was induced via monocrotaline injection (sc, 60/kg B.W.) on day one of the 23-day observational period. After that, the animals were sacrificed, hearts removed and weighed and the papillary muscles isolated to measure force of contraction (F_c). Morphological changes of pulmonary vessels were also examined.

Results

Mixed diet supplementation with l-ARG + ND prevented highly significant right ventricle enlargement induced by PAH in both, male and female rats. Weight ratios between the right ventricle (RV) on one side and the left ventricle with septum on the other (LV + S) decreased from 0.46 ± 0.016 g to 0.29 ± 0.006 g in males and from 0.63 ± 0.03 g to 0.24 ± 0.008 g in females, n = 6, p < 0.001. Additionally, PAH increased basal contractility in female groups, and each of the diet allocations (l-ARG, ND, and mixed) were found to restore contractility to control values. All diet protocols in male and female restored decreased responsiveness of the myocardium to norepinephrine in hearts obtained from rats with PAH and prevented vascular changes observed in pulmonary hypertension (thickness of blood vessels and cell infiltration).

Conclusion

Our study suggests that l-arginine, nicotinamide or both play a positive role in right ventricle function or the process reducing pulmonary vascular remodeling especially in a gender-independent way.

Non-genomic vasorelaxant effects of 17β-estradiol and progesterone in rat aorta are mediated by L-type Ca2+ current inhibition

AIM

The sex hormones 17β-estradiol (βES) and progesterone (PRG) induce rapid non-genomic vasodilator effects which could be protective for the cardiovascular system. The purpose of this study was to analyze the mechanisms underlying their vasodilator effect in rat aortic smooth muscle preparations.

METHODS

Endothelium-denuded aorta artery rings were prepared from male Wistar rats and incubated in an organ bath. The contractions of the preparation were recorded through isometric transducers. The effects of the hormones on K(+) current and L-type Ca(2+) current (LTCC) were analyzed by using the whole cell voltage-clamp technique in A7r5 cells.

RESULTS

Both βES and PRG (1-100 μmol/L) concentration-dependently relaxed the endothelium-denuded aortic rings contracted by (-)-Bay K8644 (0.1 μmol/L) or by KCl (60 mmol/L). The IC(50) values of the two hormones were not statistically different. The K(V) channel blocker 4-aminopyridine (2 mmol/L), BK(Ca) channel blocker tetraethylammonium (1 mmol/L) and K(ATP) channel blocker glibenclamide (10 μmol/L) did not significantly modify the relaxant effect of the hormones. On the other hand, the blockage of the intracellular βES and PRG receptors with estradiol receptor antagonists ICI 182,780 (1 μmol/L) and PRG receptor antagonist mifepristone (30 μmol/L), respectively, did not significantly modify the relaxant action of the hormones. In A7r5 cells, both the hormones (1-100 μmol/L) rapidly and reversibly inhibited the basal and BAY-stimulated LTCC. However, these hormones had no effect on the basal K(+) current.

CONCLUSION

The vasorelaxant effects of βES and PRG are due to the inhibition of LTCC. The K(+) channels are not involved in the effects.

Activation of the G-protein-coupled receptor GPR30 induces anxiogenic effects in mice, similar to oestradiol

RATIONALE

The influence of ovarian hormones on behaviour is well accepted, and oestrogen replacement therapy has proven to be beneficial in several cases of menopausal mood disorders. However, there are also some adverse effects of such a therapy, like anxiety and dysphoria. In fact, some women feel better at low levels of oestrogen and worse when levels fluctuate. Still, it is unclear which receptors might mediate negative emotional effects.

OBJECTIVES

The aim of this study was to identify which oestrogen receptor(s) are capable of mediating negative emotional effects and, therefore, may represent candidates responsible for the adverse side effects observed in oestrogen replacement therapy.

RESULTS

We provide evidence from mouse behavioural tests that oestrogen-induced anxiogenic-like effects might be mediated, at least in part, by the G protein-coupled receptor GPR30. The short-term application of specific agonists against the alpha and beta oestrogen receptors did not result in marked behavioural changes. In contrast, the specific stimulation of GPR30 in male and ovariectomized female mice induced anxiogenic effects. The anxiogenic effects induced by the specific GPR30 agonist G-1 were comparable (and non-accumulative) to those observed after low doses of the general oestrogen receptor agonist 17b-oestradiol in male mice, thereby reflecting the behavioural changes observed in intact female mice during early pro-oestrus.

CONCLUSIONS

Our data suggest that GPR30 induces acute anxiogenic effects of oestrogen in rodents. It is tempting to speculate that a potential imbalance in the expression of the anxiolytic beta oestrogen receptor and the anxiogenic GPR30 may also be involved in the negative symptoms of oestrogen replacement therapy in humans.