The intestinal absorption of calcium (Ca) from Ca ascorbate (Ca-AsA) was investigated in normal rats. Each animal was perorally administered either 5mg (low dose) or 10mg (high dose) of Ca in 1ml of distilled water as Ca-AsA, Ca carbonate (CaCO3), or Ca chloride (CaCl2), which were intrinsically labeled with 45Ca using 45CaCl2. The amount of radioactivity in plasma was measured periodically up to 34h after dosing, and pharmacokinetic parameters were calculated from the radioactivity in plasma. The time taken to reach the maximum 45Ca level (Tmax) did not differ among the three groups. The area under the plasma 45Ca level/time curve (AUCinfinity) value for the Ca-AsA group was significantly higher than those for the CaCO3 and the CaCl2 groups. The radioactivity at Tmax (Cmax) for the Ca-AsA group was significantly higher than those for the CaCO3 and the CaCl2 groups for the low dose, and comparable with or significantly higher than those for the CaCl2 and CaCO3 groups for the high dose. Similar results were observed for whole-body 45Ca retention. Radioactivity in the femur 34h after dosing was the highest in the Ca-AsA group and the lowest in the CaCO3 group. The rank order of solubility in water, the first fluid (pH 1.2, JP-1) of JPXIII disintegration medium, acetate buffer solution (pH 4.0), triethanolamine-malate buffer solution (pH 7.0) and ammonium chloride buffer solution (pH 10.0) at 37 degrees C was CaCl2 > Ca-AsA > CaCO3. In contrast, the rank order of the solubility in the second fluid (pH 6.8, JP-2) of JPXIII disintegration medium at 37 degrees C was Ca-AsA > CaCl2 > CaCO3. These results indicate that the absorbability of Ca from Ca-AsA is almost comparable with, or higher than, that from CaCl2 and significantly higher than that from CaCO3 because of its high degree of solubility in the intestine. Therefore, Ca-AsA would be useful as a Ca supplement with relatively high absorption from intestine.
Objective-To investigate the relation between plasma concentrations of immunoreactive endothelin and haemodynamic variables before and after percutaneous transvenous balloon dilatation of the mitral valve.Design-Prospective study. Setting-National cardiovascular cen- Reports of plasma endothelin concentrations in congestive heart failure are not consistent. An increased plasma endothelin concentration was reported in humans7 and dogs8 9 with congestive heart failure, but in one study there was no appreciable increase of plasma endothelin concentration in patients with stable but severe congestive heart failure.6 Furthermore, in dogs with experimental congestive heart failure evoked by rapid ventricular pacing, plasma endothelin concentrations in the femoral artery were raised and correlated well with the mean pulmonary capillary wedge pressure.9 This finding accords with the primary role of left atrial pressure in cardiac atrial natriuretic peptide secretion in patients with mitral stenosis.'°I Recent observations demonstrate that endothelin is expressed in the lungs and heart as well as in vascular endothelial cells,'2 13 and the widespread distribution of endothelin mRNA indicates that the peptide can be synthesised in many tissues.'1'6 These observations suggest that increased concentrations of plasma endothelin may be derived from the lungs or heart or both in states such as congestive heart failure. However, there is no information on the possible role of left atrial pressure in the secretion of endothelin from vascular endothelial cells. We studied the relations between plasma endothelin concentrations at multiple sampling sites and haemodynamic variables in patients with mitral stenosis undergoing percutaneous balloon dilatation of the mitral valve.
Patients and methods
PATIENTS AND BLOOD SAMPLINGWe studied 25 patients (seven men and 18 women; mean (SD) age, 53 (10) years) with symptomatic mitral stenosis who were in New York Heart Association functional classes II-III. They all gave their informed consent.
To evaluate the influence of intra-balloon pressure on the development of severe mitral regurgitation (> or = grade 3+), we measured intraballoon pressure during percutaneous transvenous mitral commissurotomy (PTMC) in 62 patients using the Inoue balloon catheter. The peak intraballoon pressure was 2.29 +/- 0.55 kg/cm2. Severe mitral regurgitation as a result of leaflet tear occurred in 7 patients (11%). Patients were divided into two groups those with (n = 7) and those without (n = 55) severe mitral regurgitation. Intraballoon pressure had been significantly higher in those with vs. those without severe mitral regurgitation (2.76 +/- 0.31 kg/cm2 vs. 2.23 +/- 0.55 kg/cm2, P < 0.01). Multiple logistic regression analysis revealed that the occurrence of severe mitral regurgitation was related to only the peak intraballoon pressure. These data suggest that a high intraballoon pressure is a risk factor for severe mitral regurgitation as a result of leaflet tear.
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