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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Animals, Apamin, Blood Pressure, Charybdotoxin, Disease Models, Animal, Dose-Response Relationship, Drug, Enzyme Inhibitors, Glycine, Heart Rate, Hypertension, Male, NG-Nitroarginine Methyl Ester, Potassium Channels, Calcium-Activated, Rats, Rats, Inbred SHR, Rats, Inbred WKY, Rats, Sprague-Dawley, Serine, Threonine.
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Does l-Serine lower while glycine increases blood pressure in chronic L-NAME-treated and spontaneously hypertensive rats? Context: To determine the acute hemodynamic effects of the nonessential amino acid, glycine, and its precursor, L-serine, in normotensive and hypertensive rats. Changes in mean arterial pressure and heart rate evoked by comparable intravenously administered doses (0.3-3.0 mmol/kg) of L-serine, D-serine and glycine were examined in anaesthetized normotensive 14-week-old male Sprague-Dawley, Wistar-Kyoto (WKY) rats, spontaneously hypertensive rats and WKY rats subjected to chronic nitric oxide synthase inhibition by treatment with NG nitro L-arginine methyl ester (0.7 mg/ml in drinking water for 5 days). L-Serine evoked a greater maximal fall in mean arterial pressure [L-serine vs. D-serine in Sprague-Dawley rats, mean +/- standard error of the mean values (mmHg): 30 +/- 3 vs. 20 +/- 5, P < 0.05; in control WKY rats: 46 +/- 3 vs. 30 +/- 4, P < 0.05; in NG nitro L-arginine methyl ester-treated WKY rats: 93 +/- 6 vs. 41 +/- 5, P < 0.01; in spontaneously hypertensive rats: 81 +/- 7 vs. 39 +/- 5 P < 0.01]. The effects of L-serine were significantly reduced in rats pretreated with a combination of apamin and charybdotoxin, inhibitors of the small conductance and intermediate conductance calcium-activated potassium (KCa) channels. Glycine elicited a dose-dependent fall in mean arterial pressure in normotensive WKY rats (25 +/- 4; P < 0.01) and evoked pressor responses in both spontaneously hypertensive rats (29 +/- 3; P < 0.01) and NG nitro L-arginine methyl ester-pretreated hypertensive WKY (39 +/- 5; P < 0.01) rats. Both the depressor and pressor responses to glycine were abolished by pretreatment with the N-methyl D-aspartate receptor antagonist, MK-801.
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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. Final Decision: yes