Ultrastructural pathology of ozone-induced experimental parathyroiditis. IV. Biphasic activity in the chief cells of regenerating parathyroid glands.

Sequential development of electron miscrosopic changes in the rabbit parathyroid gland was monitered during induction of parathyroiditis by 48 hours of ozone 0.75 ppm dosage regimen. By 4 to 7 days, electron microscopy revealed prominence of polyribosomes, rough endoplasmic reticulum, Golgi complex, secretory granules, microtubules, and frequent infoldings of the plasma membrane. Presumable this was the stage of parathyroid hormone synthesis. Between 14 to 18 days, ultrastructural observations showed dilatation of rough endoplasmic reticulum with continuity with annulate lamellae, disaggregation of polyribosome attached to the rough endoplasmic reticulum, and accumulation of numerous solitary free ribosomes in the cytoplasm. The dilated portion of endoplasmic reticulum contained medium electron-dense granular material, which also appeared between the intercellular spaces. The medium electron-dense material assumed to condensed appearance of basal lamina bordering the intercellular matrix. On the basis of the present observation it was concluded that the second set of ultrastructural changes signify the stage of basal lamina reconstruction. The significance of these changes as reparative responses to the inflammatory stimuli was discussed.