| Popis: |
It is well established that a thrombocytopoiesis stimulating factor (TSF or thrombopoietin) is a major controlling factor of megakaryocytopoiesis and thus thrombocytopoiesis. During the past 30 years there have been intermittent periods of active research on the hormone, with most of the decisive work occurring during the past 15 years. It should be noted that the study has been difficult, largely because of the lack of suitable assays and stable sources of the hormone. Only during the past decade have reliable assays been developed and potent sources identified. Therefore, with these assays and sources, definitive studies on the presence and characterization of the hormone have now been published and will be discussed in this review. In this chapter, a model for megakaryocytopoiesis and its controUing factors, to include the megakaryocyte-colony stimuladng factor (meg-CSF) and thrombopoietin, are presented. Since thrombopoietin is the major controlling factor of in vivo blood platelet production, it will be considered in greater detail than the other factors. Its biology, mode of action, immunology, site of production, purification, and chemical characterization will be reviewed in some detail. Although the effects of thrombopoiedn on megakaryocytopoiesis appear to be similar to those of other humoral factors with their control of specific hematopoietic hneages, there are some aspects of platelet production mechanisms that need additional discussion, e.g., the effects of hypoxia and its ability to interrupt thrombocytopoiesis and the stimulating effects of erythropoietin and other growth factors on megakaryocytopoiesis and thrombocytopoiesis. The clinical aspects of thrombopoietin, to include several disease states that are known to be associated with increased or decreased thrombopoietin titers, will be briefly mentioned, along with a brief summary and views of its future in chnical medicine. |
