Characterization of rat heart alkaline phosphatase isoenzymes and modulation of activity.

Alkaline phosphatase (ALP) is important in calcification and its expression seems to be associated with the inflammatory process. We investigated the in vitro acute effects of compounds used for the prevention or treatment of cardiovascular diseases on total ALP activity from male Wistar rat heart homogenate. ALP activity was determined by quantifying, at 410 nm, the p-nitrophenol released from p-nitrophenylphosphate (substrate in Tris buffer, pH 10.4). Using specific inhibitors of ALP activity and the reverse transcription-polymerase chain reaction, we showed that the rat heart had high ALP activity (31.73 +/- 3.43 nmol p-nitrophenol.mg protein-1.min-1): mainly tissue-nonspecific ALP but also tissue-specific intestinal ALP type II. Both ALP isoenzymes presented myocardial localization (striated pattern) by immunofluorescence. ALP was inhibited a) strongly by 0.5 mM levamisole, 2 mM theophylline and 2 mM aspirin (91, 77 and 84%, respectively) and b) less strongly by 2 mM L-phenylalanine, 100 mL polyphenol-rich beverages and 0.5 mM progesterone (24, 21 to 29 and 11%, respectively). beta-estradiol and caffeine (0.5 and 2 mM) had no effect; 0.5 mM simvastatin and 2 mM atenolol activated ALP (32 and 36%, respectively). Propranolol (2 mM) tended to activate ALP activity and corticosterone activated (18%) and inhibited (13%) (0.5 and 2 mM, respectively). We report, for the first time, that the rat heart expresses intestinal ALP type II and has high total ALP activity. ALP activity was inhibited by compounds used in the prevention of cardiovascular pathology. ALP manipulation in vivo may constitute an additional target for intervention in cardiovascular diseases.

Characterization of rat heart alkaline phosphatase isoenzymes and modulation of activity

Alkaline phosphatase (ALP) is important in calcification and its expression seems to be associated with the inflammatory process. We investigated the in vitro acute effects of compounds used for the prevention or treatment of cardiovascular diseases on total ALP activity from male Wistar rat heart homogenate. ALP activity was determined by quantifying, at 410 nm, the p-nitrophenol released from p-nitrophenylphosphate (substrate in Tris buffer, pH 10.4). Using specific inhibitors of ALP activity and the reverse transcription-polymerase chain reaction, we showed that the rat heart had high ALP activity (31.73 ± 3.43 nmol p-nitrophenol·mg protein-1·min-1): mainly tissue-nonspecific ALP but also tissue-specific intestinal ALP type II. Both ALP isoenzymes presented myocardial localization (striated pattern) by immunofluorescence. ALP was inhibited a) strongly by 0.5 mM levamisole, 2 mM theophylline and 2 mM aspirin (91, 77 and 84 percent, respectively) and b) less strongly by 2 mM L-phenylalanine, 100 mL polyphenol-rich beverages and 0.5 mM progesterone (24, 21 to 29 and 11 percent, respectively). â-estradiol and caffeine (0.5 and 2 mM) had no effect; 0.5 mM simvastatin and 2 mM atenolol activated ALP (32 and 36 percent, respectively). Propranolol (2 mM) tended to activate ALP activity and corticosterone activated (18 percent) and inhibited (13 percent) (0.5 and 2 mM, respectively). We report, for the first time, that the rat heart expresses intestinal ALP type II and has high total ALP activity. ALP activity was inhibited by compounds used in the prevention of cardiovascular pathology. ALP manipulation in vivo may constitute an additional target for intervention in cardiovascular diseases.

[Human serum alcaline phosphatase and ageing]. / Fosfátase alcalina sérica humana e envelhecimento.

BACKGROUND: In experimental ageing models an inverse relationship between age and alkaline phosphatase activity has been observed. OBJECTIVE: To characterize serum levels of alkaline phosphatase activity in humans according to age and gender. METHODS: Serum alkaline phosphatase was determined in a random sample of 203 community dwellers aged 40 or more years. RESULTS: In men (n=87) total serum alkaline phosphatase markedly increased from the 5th to the 6th decade and then stabilized. For women (n=116) there was a slight increase in total serum alkaline phosphatase from the 5th to the 6th decade, followed by a bend upward after 69 years of age. There was a significant positive correlation between total serum alkaline phosphatase and age for the whole population. CONCLUSIONS: Serum alkaline phosphatase activity appears as a biomarker of age in humans, similarly to what has been described for experimental animal models.

Alkaline phosphatase from rat liver and kidney is differentially modulated.

OBJECTIVE: To investigate the effect of inhibitors of alkaline phosphatase (ALP) and modulators of P-glycoprotein (Pgp), multidrug resistance protein (MRP) and hepatic taurocholate uptake on the activity of tissue-nonspecific ALP (TNALP) in liver and kidney. DESIGN AND RESULTS: ALP activity was determined in rat liver and kidney homogenates. Levamisole had a stronger inhibitory effect on renal TNALP than on the hepatic isoform. 1,3-dimethylxanthine (theophylline) almost abolished renal TNALP activity whereas its effect on hepatic TNALP was less intense. 3-isobutyl-1-methylxanthine (IBMX) and lidocaine produced opposite effects, activating hepatic TNALP and inhibiting the kidney isoform. Quinidine significantly inhibited renal TNALP without affecting hepatic TNALP. Kaempferol activated both liver and kidney isoforms, the effect being more pronounced on hepatic TNALP. CONCLUSIONS: a) renal TNALP seems to be more sensitive to inhibition than hepatic TNALP, b) TNALP activity studies should take into account the source of ALP isoform and c) ALP pharmacological manipulation in vivo may produce different and even opposite effects in different tissues/organs.

Physiologic concentrations of bile salts inhibit rat hepatic alkaline phosphatase but not the intestinal isoenzyme.

OBJECTIVE: The effect of bile salts on alkaline phosphatase (EC 3.1.3.1) activity from Wistar rat liver, duodenum, jejunum, and serum was investigated. DESIGN AND RESULTS: For concentrations higher than 1 mM conjugated bile salts (glycocholate, glycochenodeoxycholate, taurocholate, taurodeoxycholate, and taurochenodeoxycholate) inhibited hepatic ALP but, up to concentrations of 10 mM, had no effect on intestinal ALP. Also cholate, deoxycholate, and chenodeoxycholate, within the same concentration range, did not have any effect on intestinal ALP. ALP inhibition induced by conjugated bile salts was significantly higher in serum of starved rats than in serum of fed animals, what is in good agreement with the known higher proportion of hepatic ALP and lower proportion of intestinal ALP in serum of starved rats. CONCLUSIONS: Bile salts can, thus, be used to help discriminating between tissue-nonspecific and intestinal ALP isoenzymes and identifying pathologic conditions where the relative quantities of these isoenzymes are altered in serum. Inhibition of hepatic ALP by physiologic concentrations of bile salts may bear some relation to the bile salts effects on their own enterohepatic circulation and/or biosynthesis.

Solvent-free method for the determination of polynuclear aromatic hydrocarbons in waste water by solid-phase microextraction-high-performance liquid chromatography with photodiode-array detection.

Solid-phase microextraction (SPME) has rapidly been established among the practical alternatives for sample preparation for gas chromatography. Nevertheless polynuclear aromatic hydrocarbons (PAHs) are more effectively monitored by high-performance liquid chromatography (HPLC), but initially, there was no simple way to introduce analytes extracted by SPME into an HPLC system. A SPME-HPLC interface was developed by Supelco, which enables one to take advantages of the time and solvent savings offered by SPME. In the present work six PAHs from the European Union directives: fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene benzo[a]pyrene, benzo[ghi]perylene, indeno[1,2,3-cd]pyrene were evaluated after optimization of a sample preparation method with a 100-micron poly(dimethylsiloxane) fiber. Repeatability, reproducibility, correlation coefficients, linearity, recoveries and limits of detection where determined and are indicated.