SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Serum alkaline phosphatase was measured in ten mares during various stages of gestation. No significant change in serum alkaline phosphatase activity was detected during pregnancy. These data suggest that interpretation of serum alkaline phosphatase in horses can be made independently of their pregnancy status.
Alkaline phosphatase of the Greenland seal was purified to homogeneity, using immobilized concanavalin A. The specific activity of the enzyme is 1200-1500 mu/mg protein. The molecular mass of alkaline phosphatase as determined by electrophoresis performed under non-denaturating conditions is 260 kD, whereas that determined in the presence of beta-mercaptoethanol and SDS is 70 kD, which points to the tetrameric type of the seal alkaline phosphatase molecule. Using the atomic adsorption method, it was demonstrated that the phosphatase molecule contains four zinc atoms. Some physico-chemical parameters of seal alkaline phosphatase (pH-dependence, effects of temperature and cations on the enzyme activity, pI, thermal stability) were determined.
The inhibition of alkaline phosphatase by insulin is a finding reported by many researchers but the mechanism of this inhibition has not been studied. Since alkaline phosphatase is an important factor in the mechanism of calcification and an impairment of mineralisation has been observed in diabetes mellitus, a study was carried out to assess the effect of the hormone on alkaline phosphatase measured in chondrocytes, in matrix vesicles and in a purified enzyme preparation. Enzyme activity was inhibited by insulin. The lowest active concentration was 10(-6) M and maximal inhibition was obtained at about 10(-4) M. The inhibition is of the uncompetitive type. Full recovery of the hormone-inhibited enzyme was obtained with 10(-4) M 2-mercaptoethanol. Data suggest direct interaction between the alkaline phosphatase and insulin molecules, involving either disulfide cross linkages or the metal chelating activity of insulin.
A study of some biochemical properties of alkaline phosphatase derived from human endometrium has been undertaken. The endometrial enzyme has been shown to be different from alkaline phosphatases obtained from placenta and small intestine. Endometrial alkaline phosphatase is inhibited by sodium deoxycholate but not by L-phenylalanine; it is completely inhibited by 3 M urea. Magnesium ions have no significant effect on the endometrial enzyme. No differences in biochemical properties were observed when alkaline phosphatase from follicular phase endometrium was compared with that from luteal phase tissue. Acrylamide gel electrophoresis showed a single, constant band of enzyme at all stages of the cycle. It is concluded that, despite the cyclic appearance of alkaline phosphatase in endometrial glands and the constant presence of the enzyme in blood vessels, there is but one variety of alkaline phosphatase in human endometrium.
Human intestinal alkaline phosphatase was immunohistochemically identified and localized in the pancreas, liver and kidney by use of a monoclonal antibody specific for intestinal alkaline phosphatase isozyme and by amplified biotin-streptavidin staining. In all the examined organs, the intestinal isozyme was found to be localized in the epithelial cells of ducts: bile ducts in the liver, distal convoluted tubules and collecting tubules in the kidney and ducts in the secretory epithelium in the pancreas. In the liver the antibody also stained some sinus-lining cells. In all the examined organs the endothelial cells of the capillaries and some vessels were stained. By use of immunoelectron microscopy, intestinal alkaline phosphatase was, as expected, found to be localized to the microvillar region of the small intestine. The isozyme was abundantly expressed in the apical area of the microvilli and in membrane remnants in the fuzzy coat. Capillaries and vessels in the submucosa were also stained, as well as small vesicles in the endothelial cells. The present investigation demonstrates the expression and localization of the intestinal alkaline phosphatase in several organs, though previously believed to be expressed only in the intestine.
Serum alkaline phosphatase isoenzymes were determined quantitatively by electrophoresis on cellulose acetate in 168 patients with rheumatic diseases subgrouped for disease activity. Median values of total alkaline phosphatase and bone isoenzyme activity, as well as frequency of patients showing pathological values, increased gradually and significantly corresponding to disease activity in rheumatoid arthritis and ankylosing spondylitis, from 0% in inactive to 90% in very active forms. Bone isoenzyme was much more sensitive than total alkaline phosphatase in moderate disease activity and was also correlated to the number of involved extravertebral joints and pain in ankylosing spondylitis. No correlation was found with stage or duration of disease, age, sex, and erythrocyte sedimentation rate. Additional to bone isoenzyme, liver isoenzymes were elevated in some patients, but with only a weak correlation with disease activity. The intestinal isoenzymes were always normal. We conclude that quantitative determination of serum alkaline phosphatase bone isoenzyme activity is a major indicator for the assessment of disease activity and therapeutic monitoring in rheumatoid arthritis and ankylosing spondylitis.
Human alkaline phosphatase isozymes--the tissue-unspecific, the intestinal, and the placental alkaline phosphatases--were determined in sera by use of isozyme-specific monoclonal antibodies. The clinical utility of serum determinations of alkaline phosphatase isozymes was evaluated in patients with diseases of the gastrointestinal tract and the liver. No elevations of the different serum isozymes were observed in the intestinal diseases investigated (active Crohn's disease and ulcerative colitis). For non-malignant diseases of the liver the alkaline phosphatase isozymes presented characteristic patterns. Patients with cirrhosis due to hepatocellular diseases had markedly elevated levels of intestinal alkaline phosphatase and moderate serum activities of tissue-unspecific and placental alkaline phosphatases. In patients with liver disease with cholestatic features tissue-unspecific and placental isozyme levels were high, but the intestinal isozyme remained normal, whereas primary biliary cirrhosis was associated with high levels of the tissue-unspecific enzyme and moderate elevations of intestinal and placental alkaline phosphatases. It can be concluded that, in addition to tissue-unspecific alkaline phosphatase, intestinal and placental isozymes contribute to the total alkaline phosphatase activity for patients with liver disease. The results suggest that specific methods for the identification of alkaline phosphatase isozymes could be of value.
Alkaline phosphatase is the marker enzyme for matrix vesicles, extracellular organelles that play a major role in primary bone formation and calcification. Recently, we developed osteosarcoma x fibrosarcoma hybrids in which alkaline phosphatase expression was greatly reduced, a phenomenon known as extinction. In the present study, we used to cell hybrids, LTA-1 and LTA-5, constructed from a human osteoblast-like osteosarcoma. TE85, and a mouse fibrosarcoma, La-t-, to examine the differential distribution of alkaline phosphatase between matrix vesicles and the plasma membrane, postulated to be the parent membrane from which matrix vesicles are derived. While alkaline phosphatase in plasma membranes was extinguished, enzyme activity in matrix vesicles from LTA-1 hybrid cells was 34.2% of that present in matrix vesicles from the TE85 parent cells and 200 times that found in La-t- matrix vesicles. Matrix vesicles from LTA-5 had alkaline phosphatase levels similar to La-t-. When other membrane enzymes (phospholipase A2, 5'-nucleotidase, and Na+/K+ ATPase) were examined, hybrid matrix vesicle and plasma membrane levels were similar to those of TE85 and significantly higher than in La-t- membrane fractions. Northern analysis detected mRNA for alkaline phosphatase in TE85 cells, but not in the hybrids or La-t- cells. In contrast, reverse transcription-polymerase chain reaction (RT-PCR) revealed alkaline phosphatase mRNA in the hybrid cells, but at very low levels. Taken together, the data indicate that regulation of plasma membrane and matrix vesicle alkaline phosphatase is independent and suggest that matrix vesicle biogenesis is independent and distinct from that of plasma membrane biogenesis. Analysis of 1B- and 1L-type alkaline phosphatase mRNA by RT-PCR showed that alternate promoter usage of the alkaline phosphatase gene was not responsible for the differential localization of this enzyme in matrix vesicle. Thus, it is likely that matrix vesicle and plasma membrane alkaline phosphatase are regulated differently at a post-transcriptional level.
Alkaline phosphatase activity in the liver and intestine increases after bile duct ligation, reportedly by increased enzyme synthesis. To ascertain the mechanism of this increased synthesis in the absence of a cDNA clone encoding the enzyme, we have estimated the concentration of liver and intestinal alkaline phosphatase mRNA by translational analysis. Monospecific antiserum to rat placental alkaline phosphatase was raised. The resulting antiserum precipitated two peptides of 53 and 56 kd after translation of liver poly(A) + RNA. The precipitation of both peptides was blocked by the single 64 kd placental alkaline phosphatase. Processing of the cell-free products by microsomal membranes produced peptides of 62 and 64 kd. Antiserum to rat intestinal alkaline phosphatase also identified two peptides as products of intestinal RNA translation. After bile duct ligation, we confirmed a transient 2-fold increase in alkaline phosphatase activity in the intestine and a more constant 7-fold increase in the liver. However, the alkaline phosphatase mRNA concentration remained unchanged in both organs. We conclude that increased alkaline phosphatase synthesis after bile duct ligation results from an enhanced rate of translation of mRNA.
The susceptibility of intestinal alkaline phosphatase to DL-buthionine-S,R-sulfoximine was investigated in chicks fed a commercial diet. The results show that DL-buthionine-S,R-sulfoximine produced inhibition of intestinal alkaline phosphatase activity. This effect showed dose- and time-dependency and it was caused by either in vivo DL-buthionine-S,R- sulfoximine administration or in vitro DL-buthionine-S,R-sulfoximine incubation with villus tip enterocytes. DL-Buthionine-S,R-sulfoximine did not act directly on intestinal alkaline phosphatase but it provoked glutathione depletion which led to changes in the redox state of the enterocyte as shown by the production of free hydroxyl radicals and an incremental increase in the carbonyl content of proteins. The reversibility of the buthionine sulfoximine effect on intestinal alkaline phosphatase was proved by addition of glutathione monoester to the duodenal loop.
Alkaline phosphatase activity was histochemically localized in adult whiteflies (Bemisia tabaci B biotype, syn. B. argentifolii) with a chromogenic substrate (5-bromo-4-chloro-3-indolylphosphate) and a fluorogenic substrate (ELF-97). The greatest amount of staining was in the basal regions of adult salivary glands with additional activity traced into the connecting salivary ducts. Other tissues that had alkaline phosphatase activity were the accessory salivary glands, the midgut, the portion of the ovariole surrounding the terminal oocyte, and the colleterial gland. Whitefly nymphs had activity in salivary ducts, whereas activity was not detected in two aphid species (Rhodobium porosum and Aphis gossypii). Whitefly diet (15% sucrose) was collected from whitefly feeding chambers and found to have alkaline phosphatase activity, indicating the enzyme was secreted in saliva. Further studies with salivary alkaline phosphatase collected from diet indicated that the enzyme had a pH optimum of 10.4 and was inhibited by 1 mM cysteine and to a lesser extent 1 mM histidine. Dithiothreitol, inorganic phosphate, and ethylenediaminetetraacetic acid (EDTA) also inhibited activity, whereas levamisole only partially inhibited salivary alkaline phosphatase. The enzyme was heat tolerant and retained approximately 50% activity after a 1-h treatment at 65 degrees C. The amount of alkaline phosphatase activity secreted by whiteflies increased under conditions that stimulate increased feeding. These observations indicate alkaline phosphatase may play a role during whitefly feeding.
It has been demonstrated that dephosphorylation of the ferredoxin component of the mitochondrial 25-hydroxyvitamin D3-1-hydroxylase, as a result of a PTH-cAMP mediated activation, involves a protein phosphatase activity. However, the nature and properties of this phosphatase are uncertain. It has been proved that alkaline phosphatase, a magnesium dependent enzyme, could dephosphorylate in vitro the ferredoxin component of the 25-hydroxyvitamin D3-1-hydroxylase. Moreover, some evidence of mitochondrial localization of some alkaline phosphatases has been published. Although the existence of a levamisole inhibitable alkaline phosphatase activity has been described in renal cells, its role remains to be elucidated. In the present work, the existence of an alkaline phosphatase in mitochondrial membrane preparations from LLC-PK1 cells has been described. This alkaline phosphatase is magnesium dependent and levamisole inhibitable. Preparations of mitochondrial membrane from LLC-PK1 cells also showed 25-hydroxyvitamin D3-1-hydroxylase (1-hydroxylase) and 25-hydroxyvitamin D3-24R-hydroxylase (24-hydroxylase) activities being both enzymes responsive to the 8Br-cAMP mediated regulation. The 8Br-cAMP not only stimulated the 1-hydroxylase and inhibited the 24-hydroxylase activities but also increased the mitochondrial alkaline phosphatase activity. In the same way, the levamisole (specific inhibitor of some alkaline phosphatases) inhibited the mitochondrial alkaline phosphatase and also the 1-hydroxylase activity. In addition, the inhibition of mitochondrial alkaline phosphatase by levamisole avoids the effect of 8Br-cAMP on the 1-hydroxylase and 24-hydroxylase activities. On the other hand, the mitochondrial alkaline phosphatase and the 1-hydroxylase activities showed similar behaviour with respect to the magnesium concentrations in the incubation medium. Taking these results together it could be possible to suggest the implication of the Mg(2+)-dependent mitochondrial alkaline phosphatase activity found in LLC-PK1 cells in the regulation of the 1,25(OH)2D3 and 24,25(OH)2D3 synthesis.
Alkaline phosphatase (EC 3.1.3.1) bound to trophoblastic cells in rat placenta is activated by Mg2+ and inhibited by Zn2+ in the same way as is found with partially purified soluble alkaline phosphatase in the same tissue (PetitClerc, C., Delisle, M., Martel, M., Fecteau, C. & Brière, N. (1975) Can. J. Biochem. 53, 1089-1100). In studies done with tissue sections (6-10 micron), it is shown that alkaline phosphatase activity and labelling of active sites by orthophosphate are lost during incubation with ethanolamine at pH 9.0. Addition of Mg2+ causes total recovery of catalytic activity and active sites labelling. Zn2+ displaces and replaces at the Mg2+ binding sites. The affinity for both ions is similar, and dissociation of Zn2+ from the enzyme is a very slow process, even in the presence of Mg2+. The Zn2+-alkaline phosphatase and Mg2+-alkaline phosphatase, which only differ by the ion bound to an apparent modulator site, have the same catalytic activity at pH less than 7.0, but the Zn2+ species has little activity at alkaline pH. Phosphorylation of the enzyme by orthophosphate indicates that with both enzyme species phosphoryl intermediate does not accumulate at alkaline pH. These results suggest that with orthophosphate, the phosphorylation step is rate determining for both enzymes, and that Zn2+ affects this step to a much greater extent. It is proposed that Zn2+ and Mg2+ regulate alkaline phosphatase in rat placenta. The concentration of both ions in maternal serum and placenta suggest that such a mechanism could exist in vivo.
The present study sought to test whether inhibition of phosphotyrosine phosphatases (PTPs) would stimulate proliferation and differentiation of normal bone cells, and whether the PTP inhibitor-mediated effects would be blocked by protein tyrosine kinase (PTK) inhibitors. Three inhibitors [phenylarsine oxide (PAO), orthovanadate (VO(4)), and molybdate (MoO(4))] and two normal human bone cells with different basal differentiation status (i.e., mandible- and vertebra-derived bone cells) were used. Cell proliferation was determined with [(3)H]thymidine incorporation, and confirmed by cell counting. Bone cell differentiation was assessed by increases in alkaline phosphatase (ALP) specific activity and collagen synthesis. The three test PTP inhibitors each stimulated [(3)H]thymidine incorporation in both human bone cell types in a biphasic, dose-dependent manner with optimal doses of 20 nM PAO, 1 microM VO(4) and 2 microM MoO(4), respectively. These PTP inhibitors at mitogenic doses each significantly and reproducibly increased ALP specific activity and collagen synthesis. To determine whether the stimulatory effects of PTP inhibitors could be blocked by PTK inhibitors, the effects of tyrphostin A51 and erbstatin, two potent PTK inhibitors, on the actions of PTK inhibitors on [(3)H]thymidine incorporation and ALP specific activity were evaluated. Both tyrphostin A51 and erbstatin, which by themselves alone significantly inhibited human bone cell proliferation and increased ALP specific activity, completely abolished the stimulatory effects of each of the three test PTP inhibitors on bone cell proliferation and ALP specific activity. In conclusion, these findings confirm the premise that inhibition of PTP activities in normal human bone cells could lead to increases in cell proliferation and differentiation, effects that are independent of basal differentiation status of the cells. More importantly, this study demonstrates for the first time that the stimulatory actions of the PTP inhibitor on bone cell proliferation and ALP could be blocked by a PTK inhibitor, suggesting that the osteogenic effects of PTP inhibitors may depend on PTK activities, presumably to increase basal tyrosyl phosphorylation level. Accordingly, one should interpret results of studies using PTK inhibitors with caution in that an inhibition by a PTK inhibitor does not necessarily indicate the requirement of PTK activities, as it could also suggest involvement of an inhibition of PTPs.
The alkaline phosphatase isoenzymes in 105 patients with stage D carcinoma of the prostate who entered the National Prostatic Cancer Study were analyzed and these values were correlated to clinical response. Only patients with at least 3 measurements of alkaline phosphatase were evaluated. In 91% of patients with metastatic bone disease, bone alkaline phosphatase was elevated. Those patients with higher pre-treatment levels of alkaline phosphatase generally showed a poorer response to therapy. The results of alkaline phosphatase isoenzyme estimation indicate that these biological markers may be used in the evaluation of patients with metastatic prostatic cancer to predict and monitor their response to chemotherapy. The evaluation of bone and liver alkaline phosphatase isoenzymes in earlier stages also may be valuable.
This report deals with quantitative and qualitative investigations of alkaline phosphatase in two unrelated infants with the severe infantile form of hypophosphatasia. Both affected infants had no detectable leukocyte alkaline phosphatase activities and both sets of parents and one sibling tended to have low but variable leukocyte enzyme activities. Normal duodenal juice alkaline phosphatase activity was present in the one patient in whom it was measured and a wide range of variation in enzymic activity was observed in the stools. There was no significant difference in the stool enzyme activity between both patients with hypophosphatasia (42.01 +/- 9.77 U) and control infants (40.55 +/- 6.29 U). However, the heterozygous parents had values significantly lower than the control adults (2.10 +/- 0.47 as compared with 19.10 +/- 4.44 U). Intestinal bacteria did not contribute significantly to the stool alkaline phosphatase activity. Enzyme activity was present in the bile of one of the patients and nearly absent in that of the other. Three "inducers" of alkaline phosphatase were given to both patients (phenobarbital, vitamin A, and corticosteroid). No clinical improvement or rise in serum alkaline phosphatase activity was observed during the trial of therapy with these agents. However, a significant increase in the activity of serum acid phosphatase was demonstrated during the course of vitamin A administration, suggesting an in vivo action of vitamin A on the lysosomes through decreasing the stability of the membrane and releasing acid phosphatase to the serum. Quantitative determination of tissue alkaline phosphatases from autopsy tissues was highly variable: no activity was found in bone, lungs, or spleen of either infant; there was a discrepancy in liver and kidney alkaline phosphatase values (zero in one patient and present in the other) and activity was present in the intestinal mucosa of both. Qualitative analysis of kidney, liver, and intestinal alkaline phosphatase revealed some differences between the patients and control subjects in heat inactivation and phenylalanine inhibition (Table 3). Starch gel electrophoresis of the liver preparation of one patient disclosed a single band which had greater mobility than that of six control subjects matched for age. Liver extracts from a premature and from full term newborns showed two bands. The single band of the patient's liver enzyme corresponded to the newborn's fast moving component. In addition, the intestinal enzyme prepared from the same patient had an extra band when compared with age-matched control subjects.
Fifteen of 36 hyperthyroid patients had elevation in serum alkaline phosphatase activity. There was no difference in mean thyroxine (T4), triiodothyronine (T3), age, or duration of illness between the groups with high alkaline phosphatase and normal alkaline phosphatase levels. After treatment, serum alkaline phosphatase levels rose as T4 levels declined; at 3 months, the mean serum alkaline phosphatase value rose from 7.1 Bodansky units to 10.3 Bodansky units (P less than 0.005), while the mean T4 value fell from 18 microgram/dl to 7.2 microgram/dl (P less than 0.005). In some patients, serum alkaline phosphatase values have remained elevated for more than 1 year, despite continued normality in thyroid variables. Before therapy, isoenzyme patterns analyzed by polyacrylamide gel electrophoresis were qualitatively normal. As therapy was instituted, the isoenzyme patterns changed markedly, with increased amounts of bone alkaline phosphatase appearing in the serum as T4 levels were declining and total alkaline phosphatase was rising. Thyroid tissue homogenates from patients with Graves' disease were found to have very low levels of alkaline phosphatase activity and an isoenzyme pattern quite distinct from that found in the serum.
The changes in serum alkaline phosphatase that are of main diagnostic importance result from increased entry of enzyme into the circulation. This results from increased osteoblastic activity in bone disease, and increased synthesis of alkaline phosphatase by hepatocytes in hepatobiliary disease. The liver and bone forms of alkaline phosphatase are differently-glycosylated forms of a single gene product. The main value of their specific estimation is found in patients in whom bone and liver diseases co-exist, for example, as a result of cancer. Abnormal expression of genetically-distinct alkaline phosphatase isoenzymes is valuable in monitoring cancers, particularly germ-cell tumors. These isoenzymes include Regan and Nagao isoenzymes, which correspond respectively to normal placental and placental-like alkaline phosphatases, and the Kasahara isoenzyme which appears to result from re-expression of a fetal intestinal alkaline phosphatase gene.