[Are Stannius corpuscles the parathyroid glands of teleost fishes? Ultrastructural, cytologic and immunocytochemical arguments].

Parathyrin of Stannius corpuscles (PCS), glands which are restricted to Holostei and Teleostei, is closely related to mammalian parathyrin (PTH) secreted by the parathyroids [( 6] to [9]). In unstimulated and stimulated CS we have shown the same structure and cellular types that are described in mammalian parathyroids. We observed three types of cells; the two sorts of cells already described [14] present such a difference of density (Fig. 1) that type I may be compared to chief dark cells and type II to chief light cells. The difference between these two forms was particularly marked in activated CS; a similar observation has been reported concerning PT [15]. Furthermore, we have detected a third type of cell present either singly in unactivated CS or in small groups between chief cells in activated CS. They showed all the characteristics of oxyphil cells [17]; they present an extremely dense cytoplasm with numerous mitochondria and a typical stellate form with cytoplasmic processes extending between chief cells (Figs. 2, 3). In CS of untreated eels, we have shown by means of indirect immunocytology (using an immunserum raised against the active fragment 1-34 bPTH) that the immunostained reaction product was limited to dilated cisternae and ribosomes of the rough endoplasmic reticulum and to most of the granules in all the chief cells (Figs. 4, 5). No immunoreaction was observed in Golgi area. Oxyphil cells did not present an immune localization of PCS. CS are structurally and cytologically similar to mammalian PT; furthermore their chief cells synthesize, stock and secrete a substance immunologically similar to mammalian PTH; the exact function of oxyphil cells has to be demonstrated.