Platelets, acid phosphatase

The adult male prostate contains abundant acid phosphatase which it secretes into the semen. The production of this enzyme is governed by the circulating levels of androgenic hormones. Castration or estrogen administration markedly reduces the prostatic urinary acid phosphatase of males. Other organs such as the liver, kidney, spleen, red cells and platelets also contain significant amounts of acid phosphatase. 

The substrate phenyl phosphate, which is hydrolyzed by the serum acid phosphatases originating from many tissues, has been used in most of the published studies. Total serum acid phenylphos-phatase is elevated in diseases of the liver, disease of bone such as Paget s disease, and several blood dyscrasias, especially those involving platelets (99>100). 

Babson proposed a-naphthyl phosphate as an essentially specific substrate for the activity of prostatic acid phosphatase in serum (104). However Marshall, Price, and Amador found that this substrate is not specific for the prostatic enzyme because urine of human females contain 50 times more acid a-naphthyl phosphatase than male serum and 50% as much activity as male urine. Platelets have significant activity and the serum activity can increase to abnormal values following clotting. These workers also observed elevated activities in females with skeletal metastases of the breast. In 50 hospitalized male patients who had no evidence of prostatic cancer and 25 hospitalized female patients, the incidence of false positive results was 12%, a magnitude sufficient to preclude meaningful clinical interpretation (105). 

Lysis of formed blood elements other than erythrocytes may produce elevations in serum or plasma constituents. Platelet breakdown during blood collection can introduce enzymes into the plasma (Z3). Aldolase activity is very high in platelets (Dl), and elevations of acid phosphatase in myeloproliferative disease are probably the result of platelet lysis (B6). 

The slight but definite elevations of serum acid phosphatase activity in conditions such as thrombocytopenia (02, Zl), Gaucher s disease (T6, T8), or various myeloproliferative diseases (B6) indicate the possibility that platelets, the marrow, and the reticuloendothelial system may also be sources of acid phosphatase. These aspects will be discussed more fully later in the review. 

The remaining half of the sample collected in the silicone-treated glassware was transferred to ordinary glass and allowed to clot at room temperature for 30 minutes, as is usually done to obtain serum for acid phosphatase determinations. The mean values and their standard deviations for serums from platelet-poor plasma from various groups of subjects were as follows in Bodansky units 28 normal women, 0.094 0.009 23 normal men, 0.109 0.021. The corresponding values for ordinary serum acid phosphatase were 0.226 0.13 and 0.278 0.27. It appeared, therefore, that approximately 60% of the acid phosphatase in serum arises from the liberation of this enzyme from platelets as a result of clotting. 

In essence, then, these investigators felt that the plasma acid phosphatase activity, unobscured by in vitro destruction of platelets, could reflect the contribution of acid phosphatase from in vivo platelet destruction in various types of thrombocytopenias. To summarize, in thrombocyto-... 

However, Cooley and Cohen (C9) studied nine cases of idiopathic thrombocytopenic purpura in. which they failed to find any consistent correlation between the plasma acid phosphatase activities and platelet counts. Cohen et al. (C6) had shown that this condition could be classi-fifed into two major types, destructive and nondestructive, comprising 80% and 20%, respectively, of the total. In sequential studies of their various patients, Cooley and Cohen (C9) did not find any increased plasma acid phosphatase activity in those showing the destructive type, although in two cases of nondestructive (hypoplastic) thrombocytopenias, the plasma acid phosphatase activities were usually normal or low. Cooley and Cohen (C9) also found that in a group of eight patients with secondary (nondestructive) thrombocytopenias with nearly normal platelet life-spans (mostly 5-7 days) the plasma acid phosphatase levels tended to be low and to be correlated with the platelet count. 

The term myeloproliferative disorders has been applied to all those conditions which are characterized by proliferation of cells in bone marrow or in other sites of extramedullary blood formation. The overgrowth is self-perpetuating and involves one or more lines of bone marrow elements (myelocytic, erythrocytic, megakaryocytic) and cells like fibroblasts derived from the reticulum. We have already mentioned some of these conditions, for example, chronic granulocytic leukemia and myeloid metaplasia, in connection with our discussion on the relationship between serum acid phosphatase and the platelet count. 

The acid phosphatases include all phosphatases that hydrolyze phosphate esters with an optimum pH of less than 7.0. They are present in the lysozymes of the secretory epithelial cells. Although acid phosphatase is produced primarily by the prostate gland, it is also found in erythrocytes, platelets, leukocytes, bone marrow, bone, liver, spleen, kidney, and intestine. 

Time (months) N Hemoglobin (g/dL) Platelets (xl03/mm3) Acid Phosphatase (U/L)... 

Nncleotidase Acid lahUe snhunit of IGFBP Acid phophatase, tartrate resistant Acid phosphatase, prostatic Actin heta (from platelets)... 

Polasek J, Duckert F (1971) Diagnosis of quinine hypersensitivity, use of platelet factor 3 and acid phosphatase availability tests. Acta Haematol (Basel) 45 35 364 Provost TT, Jillson OF (1967) Ethylenediamine contact dermatitis. Arch Dermatol 96 231-234... 

The acid phosphatase (ACP) method, developed by Bellavite et al. [151], is based on acid phosphatase platelet activity. Acid phosphatase is a stable enzyme present in platelets. This method is similar to the LDH method. It uses regular PRP and the same Triton-X to completely lyse attached platelets. But in this test, a different enzyme (acid phosphatase) is measnred. On addition of p-nitrophenyl phosphate snbstrate, acid phosphatase converts the snbstrate into p-nitrophenol, which can be easily measnred by a photospectrometer at a wavelength of 405 nm. Side-by-side comparison of both DCH and ACP assays snggests that the ACP assay is better than the LDH assay in terms of reproducibility [152]. 

Similar observations regarding differences between the lysosomal and microsomal acid phosphatase have been reported in blood platelets (Walter et al., 1971 Kaulen and Gross, 1971). The lysosomal acid phosphatase of pig blood platelets splits preferentially yS-glycerophosphate, having a pH optimum at 5.1 and is relatively more stable at 50°C. The microsomal enzyme has a higher specificity for p-nitrophenyl phosphate, having a pH optimum at 6.0 and is less stable at 50 C. 

A group of enzymes which hydrolyse phosphate esters at optimal pHs of below 7.0. Acid phosphatases are found in erythrocytes, platelets, liver, spleen, bone and, in males, in the prostate gland. Prostatic acid phosphatase constitutes about one third of the total acid phosphatase activity present in serum from normal male subjects. 

Zieve, P.D. and Solomon, H.M., The effect of hematoporphyrin and light on human platelets. 3. Release of potassium and acid phosphatase,/. Cell Physiol., 68, 109,1966. 

Registration of adverse effects with Lorenzo s oil has been hampered by the absence of controlled trials. In 22 patients treated for at least 12 months, although Lorenzo s oil did not seem to be beneficial, there were possible adverse effects, such as mild increases in liver enzymes (55%), thrombocytopenia (55%), gastrointestinal complaints (14%), and gingivitis (14%). Furthermore, there were falls in hemoglobin concentration and leukocyte count, and an increase in the plasma alkaline phosphatase concentration the reduction in platelet count did not result in hemorrhage (1). Whether some of the adverse effects of Lorenzo s oil are due to low concentrations of essential fatty acids or caused by reduced dietary fat intake is not known. 

Salvidio, E., Biochemical aspects of blood platelets (peptidase, nucleotidase, acid and alkaline phosphatase activity in normal subiects, during menstruation and in some hemorrhagic disorders). Acta Haematol. 11, 301-308 (1954). 

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