Cellular localization of endothelial alkaline phosphatase reaction product and enzyme protein in the myocardium.

Abstract

Myocardial capillary endothelial cells, arteriolar endothelial cells, and the arterial adventitia show positive alkaline phosphatase (AP) enzyme reaction and immunoreactivity in both rat and human heatts. In guinea pigs, however, capillary endothelial staining is discontinuous and arterial adventitia is negative. The ultrastructural correlate of discontinuous capillary staining is a pronounced labeling of pericytes in guinea pig heart and relatively weak endothelial staining. In rat and human heart, enzyme reaction products are localized mainly on plasma membranes and cytotic vesicles of endothelial cells.Comparison of two strains of rat reveals a more dense deposition of enzyme reaction product along the luminal and particularly along the abluminal plasma membrane of SpragueDawley rats than of Wistar rats. Quantitative analysis of immunogold labeled anti-AP antibody density confiims the pronounced polarity of capillary endothelial cell labeling in Sprague-Dawley rats. More than 80% of total endothelial AP protein in Sprague-Dawley rats is localized over the abluminal plasma membrane and basal lamina, as compared with less than 30% in Wistar rats. Moreover, the total endothelial cell labeling is almost sixfold higher in SpragueDawley than in Wistar rats. Total endothelial labeling and proportion of labeling on the abluminal endothelial plasma membrane in human hearts is intermediate between the two strains of rat. The strain and species differences in enzyme distribution could provide important information concerning enzyme function. (JHstochem Cytochem 41:1813-1821, 1993)

Pericytes resident in postnatal skeletal muscle differentiate into muscle fibres and generate satellite cells

“…AP is broadly expressed in many pre-and postnatal tissues, and in different cell types such as osteoblasts 37 , embryonic stem cells 38 , bone marrow stroma cells 39 , liver and kidney cells 40 , granulocytes 41 and B cells 42 ; however, in postnatal mouse striated muscles, AP is expressed only by vessel-associated cells, in both endothelial cells and pericytes, as previously reported 9,[14][15][16] , and exhaustively confirmed in this work through a variety of histochemical and immunochemical methods. Most importantly, by using virtually all possible experimental approaches, we demonstrated that both AP and Cre expression are invariably absent in quiescent satellite cells, as well as in proliferating and differentiating myogenic cells in vitro or in vivo, even after cardiotoxin-induced damage.…”

“…In preliminary studies, we examined in great detail the expression of AP in postnatal and adult skeletal muscle. AP expression is robust and widespread in tissues such as intestine, bone and liver, whereas it is restricted to the micro-vasculature of other tissues, such as striated muscles, in many species [14][15][16] including human 9 . We performed extensive immunofluorescence, confocal analysis on adult and juvenile skeletal muscle to confirm AP expression in vessel-associated cells.…”

Characterization of rat heart alkaline phosphatase isoenzymes and modulation of activity

“…Autofluorescence of vascular tissue did not allow us to visualize ALP in blood vessels. Nevertheless, the presence of Int-ALP in the human vascular compartment of different organs has already been reported by Domar et al (12) and the presence of Tn-ALP in both the heart vascular compartment and muscle has already been reported by Schultz-Hector et al (5). Müller et al (23) reported an increase of ALP activity, after a single injection of isoprenaline into the right atrium, particularly on the Schwann cell and its membranes, membranes enveloping nerve axons, the sarcolemma of the muscle cell and the fibrocyte cell surface.…”

“…Although we have used a polyclonal antibody against P-ALP and Int-ALP, only Int-ALP was detected since rats do not express P-ALP (2,5). A 60-min incubation was performed with the secondary antibody (donkey anti-goat IgG-FITC, sc-2024, from Santa Cruz Biotechnology, diluted 1/200) at room temperature.…”

“…More recently, it has been proposed that ALP regulates lipid transport (4). ALP expression in vascular endothelia of small arterioles in the Characterization of rat heart alkaline phosphatase www.bjournal.com.br brain and heart, which normally do not mineralize, could contribute to vascular hardening and calcification that could, in turn, be related to vascular aging and vascular disease (1,5).…”