[Ultrastructural and metabolic characteristics of the thyrocytes exposed to cyclophosphane]

Ultrastructural, morphometric and metabolic characteristics were studied in thyrocytes of 96 mice treated with immunosuppressing and cytostatic drug cyclophosphamide (CY), injected intraperitoneally every other day either for a short time (up to 6 days) in high doses (400 mg/kg) or for a long time (up to 70 days) in moderate doses (40 mg/kg). High doses of CY caused the reduction in thyrocyte height, NADH-diaphorase activity in their cytoplasm and protein content in the follicular colloid as compared to these parameters in a control group. The cisterns of rough endoplasmic reticulum (RER) underwent swelling and deformation with the loss of electron density of their contents. This was accompanied by mitochondrial swelling with matrix clarification and disorganization of cristae and an increase in the amount of cytoplasmic lipid droplets. Following long-term administration of CY in moderate doses the thyrocyte height exceeded that one in control group, while the NADH-diaphorase activity changed insignificantly and protein concentration in colloid increased. In the majority of thyrocytes the nucleus and major organelles retained their normal structure, while in some cells the cisterns of RER appeared dilated. Acid phosphatase activity was unchanged in both experimental groups. Thus, despite the approximately equivalent total CY dose in experimental groups, its damaging effect on thyrocytes was expressed much less in animals receiving the moderate doses of CY, that, probably, could be explained by the lack of CY cumulative effect and high rate of its metabolic degradation and clearance.