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Acute metabolic effects of nitrogen mustard and thiotepa on rabbit articular cartilage and synovium
Abstract:
Metabolic alterations in immature rabbit joint tissue were examined following in vitro and in vivo exposure to the alkylating agents Thiotepa and nitrogen mustard. Brief exposure in vitro to either agent resulted in marked suppression of incorporation of radiolabeled precursors of protein, RNA, and glycosaminoglycan synthesis in articular cartilage, which was partially reversible after Thiotepa exposure. In vivo, nitrogen mustard has little effect on synovium and transient inhibitory effects on cartilage vital processes, whereas Thiotepa caused a prolonged inhibition of synovial metabolism with little effect on cartilage. Autoradiographic localization of labeled agents indicated that synovial tissue and cartilage were readily penetrated by nitrogen mustard, but only a few synovial lining cells and superficial chondrocytes were labeled with 35S-Thiotepa. Furthermore, trypsin significantly reduced labeling of cartilage with 14C-nitrogen mustard. These data suggest that alkylating agents differentially affect metabolic processes in joint tissues in vivo and that with Thiotepa, this interference occurs primarily in the synovium. The degree of interference is apparently dependent upon the time of exposure to the agents and the relative DNA-RNA synthetic activity of the joint tissue.
Insights
Alkylating agents Thiotepa and nitrogen mustard impact immature rabbit joint tissue metabolism differently. Thiotepa primarily affects synovial metabolism, while nitrogen mustard has minimal impact on synovium but transiently affects cartilage.
Area of Science:
- Biochemistry
- Pharmacology
- Orthopedics
Background:
- Alkylating agents are used in cancer therapy and can have toxic effects on various tissues.
- Understanding the specific effects of these agents on developing joint tissues is crucial for assessing potential long-term consequences.
Purpose of the Study:
- To investigate the metabolic effects of Thiotepa and nitrogen mustard on immature rabbit articular cartilage and synovium.
- To compare the in vitro and in vivo effects of these alkylating agents on joint tissue metabolism.
Main Methods:
- Exposure of immature rabbit joint tissues to Thiotepa and nitrogen mustard in vitro and in vivo.
- Measurement of radiolabeled precursor incorporation into protein, RNA, and glycosaminoglycan synthesis.
- Autoradiographic localization of labeled agents within synovial and cartilage tissues.
- Assessment of agent penetration and effects using enzymatic digestion (trypsin).
Main Results:
- In vitro exposure suppressed precursor incorporation in articular cartilage, with partial reversibility for Thiotepa.
- In vivo, nitrogen mustard had minimal effects on synovium but transiently inhibited cartilage metabolism.
- Thiotepa in vivo prolonged synovial metabolic inhibition with minor cartilage effects; agent penetration varied, with Thiotepa primarily labeling superficial cells.
Conclusions:
- Alkylating agents differentially impact joint tissue metabolism in vivo, with Thiotepa primarily affecting synovial metabolism.
- The extent of metabolic interference depends on exposure duration and the tissue's DNA-RNA synthetic activity.
- Differential penetration and cellular effects of Thiotepa and nitrogen mustard contribute to their distinct impacts on joint tissues.