Abstract-L-serine is a precursor of central neurotransmitters. Its cardiovascular effects are largely unstudied. We compared the in vitro effects of L-serine and acetylcholine in phenylephrine-constricted third-order branches of mesenteric arterioles in the NO synthase inhibitor N G -nitro L-arginine methyl ester (L-NAME), pretreated hypertensive rats, and a control group of normotensive male Sprague-Dawley rats. The changes in mean arterial pressure and heart rate evoked by acute intravenous infusion of either L-serine (0.1 to 3.0 mmol/kg) or acetylcholine (0.1 to 10.0 nmol/kg) were determined in anesthetized rats. L-serine evoked concentration-dependent (10 to 200 mol/L) vasodilatation in endothelium-intact but not in endotheliumdenuded vessels. It was abolished by the inclusion of a combination of apamin (SK Ca channel inhibitor) and TRAM-34 (IK Ca channel inhibitor) or ouabain (Na ϩ pump inhibitor) and Ba 2ϩ (K ir channel inhibitor) or when the vessels were constricted by potassium chloride. The maximal response to L-serine was higher in the L-NAME treatment group (control 20% versus L-NAME 40%) in relation to the maximal response to acetylcholine (control 93% versus L-NAME 79%). L-serine evoked a rapid, reversible, dose-dependent fall in mean arterial pressure without increasing heart rate and was more pronounced in L-NAME-treated rats (maximal response: Ͼ60 mm Hg) than in the control rats (maximal response: 25 mm Hg). This was inhibited (PϽ0.01) by apaminϩcharybdotoxin pretreatment. The in vitro and in vivo data confirm that L-serine promotes vasodilatation in resistance arterioles and evokes a greater fall in mean arterial pressure in NO synthase-inhibited hypertensive rats via activation of apamin and charybdotoxin/TRAM-34-sensitive K Ca channels present on the endothelium. Key Words: amino acids Ⅲ blood pressure Ⅲ endothelium Ⅲ hypertension Ⅲ vasodilation T he nonessential amino acid L-serine biosynthesized from glycine or threonine and the metabolism of glucose, other than being a neurotrophic factor, is a precursor for nucleotides, phospholipids, and central neurotransmitters such as glycine, serotonin, and D-serine. 1-3 L-Serine treatment has been attempted in the management of schizophrenia, depression, and chronic fatigue syndrome and for preventing microcephaly, psychomotor retardation, and seizures encountered in rare inborn errors of L-serine biosynthesis. 2,3 Recently, N-arachidonoyl L-serine was shown to promote endothelium-dependent vasodilatation in isolated rat arteries. 4 This study failed to address whether L-serine itself would promote vasodilatation or regulate blood pressure (BP). Previous studies have shown that the amino acid taurine reduces BP by reducing sympathetic discharge, oxidative stress, and increased salt excretion in hypertensive animals and patients. [5][6][7][8][9] There are no reports on the direct cardiovascular effects of L-serine. Therefore, we investigated the in vitro effect of L-serine using third-order branches of rat mesenteric arterioles constricted with phenyl...

The profound stereo-selective antihypertensive effect of L-serine is neither mediated nor mimicked by glycine. It does not require N-methyl D-aspartate receptor activation by glycine but likely involves activation of endothelial KCa channels. L-Serine is a potential antihypertensive agent.

The aim of the present study was to determine the nutritional value of Phalaris minor seeds in comparison to conventional cereal grains. P. minor seeds had higher ether extract (6.3%), total ash (7.5%), acid insoluble ash (AIA, 4.5%), acid detergent fibre (ADF, 10.2%), cellulose (5.5%), acid detergent lignin (ADL, 2.0%), neutral detergent insoluble crude protein (NDICP, 4.0%) and acid detergent insoluble crude protein (ADICP, 2.7%) content in comparison to conventional cereal grains. The crude protein of P. minor seeds (12.3%) was similar to that of wheat (12.0%), but higher than other conventional cereal grains including maize (9.0%). The amino acid composition of P. minor seeds was more or less similar to conventional cereal grains. P. minor seeds had a superior mineral profile (Ca, P, Na, K, Mg, Fe, Cu, Zn and Mn) than conventional cereal grains. In vitro evaluation revealed that net gas production was lowest (P less than 0.05) in P. minor seeds (216.37 L/kg DM/24 h). The methane production (L/kg DM/24 h)from P. minor seeds (43.03)was lower (P less than 0.05) than that from wheat (54.33) and barley (57.35). The organic matter digestibility of P. minor seeds (83.27%) was similar to that of barley (81.69%).It was concluded that P. minor seeds could be considered as potential source of nutrients for livestock.