Regulation of vascular tone in animals overexpressing the sarcolemmal calcium pump.

The mechanisms governing vascular smooth muscle tone are incompletely understood. In particular, the role of the sarcolemmal calcium pump PMCA (plasma membrane calmodulin-dependent calcium ATPase), which extrudes Ca2+ from the cytosol, and its importance compared with the sodium/calcium exchanger remain speculative. To test whether the PMCA is a regulator of vascular tone, we generated transgenic mice overexpressing the human PMCA4b under control of the arterial smooth muscle-specific SM22alpha promoter. This resulted in an elevated systolic blood pressure compared with littermate controls. In PMCA-overexpressing mice, endothelium-dependent relaxation of norepinephrine-preconstricted aortic rings to acetylcholine did not differ from wild type controls (76 +/- 8% versus 79 +/- 8% of maximum relaxation; n = 12, n.s.). De-endothelialized aortas of transgenic mice exhibited stronger maximum contraction to KCl (100 mmol/liter) compared with controls (86 +/- 6% versus 68 +/- 7% of reference KCl contraction at the beginning of the experiment; p <0.05). Preincubation of de-endothelialized vessels with the nitric oxide synthase (NOS) inhibitor l-NAME (l-N(G)-nitroarginine methyl ester) (10-5 mol/liter) resulted in a stronger contraction to KCl (p <0.05 versus without l-NAME), thus unmasking vasodilatory effects of inherent NO production. Maximum contraction to KCl after preincubation with l-NAME did not differ between PMCA mice and controls. In analogy to the results in PMCA-overexpressing mice, contractions of de-endothelialized aortas of neuronal NOS-deficient mice to KCl were significantly increased compared with controls (151 +/- 5% versus 131 +/- 6% of reference KCl contraction; p <0.05). In conclusion, our data suggest a model in which the sarcolemmal Ca2+ pump down-regulates activity of the vascular smooth muscle Ca2+/calmodulin-dependent neuronal NOS by a functionally relevant interaction. Therefore, the PMCA represents a novel regulator of vascular tone.

Increase in nitric oxide bioavailability improves endothelial function in endothelin-1 transgenic mice.

BACKGROUND: Endothelin-1 (ET-1) has been described as a very potent vasoconstrictor. Nevertheless, transgenic mice overexpressing ET-1 have been shown to exhibit normal blood pressure. We thus hypothesized that vascular ET-1 effects may be antagonized by increased activity of other regulatory systems, such as the increase in bioavailability of the endothelial counterpart of ET-1, nitric oxide (NO). METHODS: Endothelium-dependent and -independent vascular function was assessed as relaxation/contraction of isolated preconstricted aortic rings to acetylcholine (10(-10)-10(-4) mol/l), sodium nitroprusside (10(-10)-10(-4) mol/l), ET-1 (10(-10)-10(-7) mol/l) and big ET-1 (10(-10)-10(-7) mol/l), respectively, in ET-1 transgenic mice and corresponding controls. To unmask the impact of the NO system, we furthermore analysed vessel rings incubated in vitro with the NO-synthase inhibitor L-N(G)-nitroarginine methyl ester (L-NAME, 10(-4) mol/l). RESULTS: Maximum endothelium-dependent relaxation was enhanced in ET-1 transgenic mice (93+/-3% vs 84+/-4% for wild-type littermates; P<0.05) and was inhibited by preincubation with L-NAME in both ET-transgenic mice and wild-type littermates (11+/-5% vs 9+/-4% maximum relaxation, respectively). Endothelium-independent relaxation was similar among all groups. Maximum vascular contraction to ET-1 and big ET-1 was reduced in ET-1 transgenic mice (P<0.05 vs wild-type littermates). Preincubation with L-NAME reduced this difference, indicating the involvement of augmented NO availability. Correspondingly, urinary nitrate/nitrite excretion was significantly elevated in ET-1 transgenic mice. CONCLUSIONS: These data suggest that in transgenic mice overexpressing ET-1, increased NO bioavailability counteracts the contractile potency of elevated ET-1 levels and leads to an improvement of endothelium-dependent relaxation. Thus, in the presence of an activated ET system, up-regulation of NO production may be capable of maintaining vascular tone in a normal range and therefore may prevent the development of hypertension.

Composition and antimicrobial activity of the essential oil of Achillea multifida.

The composition of the water-distilled essential oil of Achillea multifida (DC.) Boiss. (Compositae) was analysed by GC and GC/MS. Fifty-eight compounds were identified representing 93.9 % of the total oil. alpha-Thujone (60.9 %), beta-thujone (9.1 %), sabinene (4.1 %) and camphor (3.7 %) were characterised as the main constituents. The essential oil was tested for its antimicrobial activity using a micro-dilution assay resulting in the inhibition (MIC: 62.5-250 microg/ml) of human pathogenic bacteria and yeast.