Platelets as a source of serum acid nitrophenylphosphatase

Lysosomal concept of platelet secretion--revisited

Certain morphological and biochemical aspects of platelet secretion are discussed. Based on own experiments and review of the literature a hypothesis is forwarded that platelet secretory granules or rather storage organelles can be viewed as secondary lysosomes participating in platelet endocytosis and exocytosis. Formation of the platelet thromboplastic activity, so called PF3, is linked to the platelet storage organelles disintegration and lypolysis during their exocytosis through the platelet plasma membrane.

Tissue damage in sickle cell disease as assessed by serum acid phosphatase

The extent of tissue damage caused by vaso-occlusion in sickle cell disease in those organs rich in acid phosphatase was assessed by measuring serum acid phosphatase in 33 patients with homozygous sickle cell disease Hb-SS (sicklers) and comparing the result with that of 31 persons with normal haemoglobin-AA (non-sicklers) matched for age and sex. The result showed a decrease in the level of total, labile and tartrate-resistant serum acid phosphatase in sicklers compared to non-sicklers, though the decrease is not statistically significant (p greater than 0.1). Though serum acid phosphatase is unlikely to be a useful index for the assessment of organ damage, the result is in consonance with reported decreases in other body secretions such as serum testosterone or aldosterone due to organ damage by vaso-occlusion of the micro-circulation by sickled red cells in sickle cell disease.

Elevated bone marrow acid phosphatase: the problem of false positives

Bone marrow acid phosphatase values were studied in 24 patients (12 men and 12 women) selected at random, including 6 at autopsy. False positive results were noted in 8 of the 18 patients who were alive and in all 6 patients studied at autopsy. The possible causes for these falsely elevated results are discussed. The bone marrow acid phosphatase is a test of poor specificity and should not be used as the sole test on which vital decisions regarding management of the patient are based.

Cytochemical localization of lysosomal enzymes in rat megakaryocytes and platelets

Platelets secrete lysosmal enzymes during the "platelet release reaction" early in clot formation. This study was undertaken to identify primary lysosomes of platelets and to detemine their origin in megakaryocytes. Using electron microscopy and cytochemistry, we localized two lysosomal enzymes, arylsulfatase and acid phosphatase, in megakaryocytes and platelets of normal and thrombocytopenic rats. In platelets and mature megakaryocytes, reaction product for both enzymes is confined to vesicles measuring 175-250 nm. These vesicles, which are primary lysosmes, first appear in the earliest recognizable megakaryocytes and increase in number during cellular maturation. In immature and maturing megakaryocytes, arylsulfatase and acid phosphatase can also be demonstrated in an organell similar to GERL (Golgi-endoplasmic reticulumlysosome), i.e., single smooth-surfaced cisternal with associated vesicles near the stacked Golgi cisternae. Scant reaction product for acid phosphatase is also sometimes seen in Golgi cisternae and endoplasmic reticulum. No reaction product was found in alpha-granules at any stage of megakaryocyte maturation, nor in alpha- or serotonin granules of platelets. Thus, our findings indicate that the primay lysosomes of megakaryocytes and platelets are small vesicles derived from GERL early in megakaryocyte differentiation. They can be indentified only after cytochemical staining and are distinct from both alpha- and serotonin granules.

Studies on human platelet granules and membranes

Images

Acid Phosphatase in Serum: Increase in Acute Myocardial Infarction

Ten consecutive cases of acute transmural myocardial infarction were accompanied by a rise of 50 to 400 percent in the serum acid phenylphosphatase. The increase in phosphatase began several hours after onset of symptoms and lasted 3 to 5 days. A similar rise was seen during the acute stages of other thromboembolic diseases. While the mechanism by which this acid hyperphenylphosphatasia occurs is not clear, platelets may play an important role.

Encrustation and atherosclerosis: the analogy between early in vivo lesions and deposits which occur in extracorporeal circulations

A study was made of the relation between the pattern and topography of thrombus formation in models of various vessel configurations coupled into extracorporeal shunts in swine and the development of atherosclerosis at corresponding sites on swine aortas. The pattern and distribution of deposits formed in the models were strikingly similar to the pattern and distribution of incipient atherosclerosis at comparable sites in the vascular tree. The earliest and only consistent component of the flow chamber deposits was the blood platelet. The platelet deposits would frequently stain with oil red O. The cholesterol level of washed human platelets was found to show a good correlation with that in the plasma. This evidence suggests that deposition of particulate matter (chiefly platelets), largely determined by the hydraulic factors, may be an important factor in the early, as well as later, stages of atherosclerosis.