Co-localization and secretion of parathyrin of Stannius corpuscles (immunoreactive parathyroid hormone) and of secretory glycoproteins including secretory protein-I in the European eel (Anguilla anguilla L.).

Until recently, teleosts were considered to be devoid of parathyroids. We showed recently that the corpuscles of Stannius, that structurally have features in common with the parathyroid gland, produce a molecule resembling mammalian parathyroid hormone (PTH). We refer to this molecule as parathyrin of corpuscles of Stannius (PCS). Parathyroid secretory protein-I (SP-I) is an acidic glycoprotein, probably identical to adrenal chromogranin A, that is co-stored and co-secreted with PTH. In the present study, PCS was localized in secretory granules of fresh water eels by immunocytochemistry. In addition, several glycoproteins were identified in these granules by periodic acid-Schiff staining and/or concanavalin A lectin binding. One of the glycoproteins that was positive with periodic acid-Schiff, but not with concanavalin A, cross-reacted with antisera to bovine parathyroid secretory protein-I. When the eels were made hypercalcemic by injecting calcium or pituitary extract, there was a coincidental translocation of the PCS, immunoreactive SP-I and the glycoproteins, suggestive that these granules were undergoing exocytosis. Immunoblot analysis of saline extract of the corpuscles of Stannius confirmed that immunoreactive SP-I was present in the tissue. It exhibited a molecular mass of about 55 kDa compared to about 70-80 kDa exhibited by mammalian SP-I when analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis.

Immunocytochemical detection in eel corpuscles of Stannius of a mammalian parathyroid-like hormone.

Stannius corpuscles of the eel synthesize and secrete a mammalian parathyroid-like hormone called parathyrin of CS (PCS). PCS has been localized in the cytoplasm of all cells in the corpuscles, detection being by indirect immunofluorescence with an antiserum anti-1-84 bovine hormone (PTH). The specificity of the reaction was demonstrated by inhibition of the fluorescent staining with 1-84 bovine PTH and the active fragment 1-34 of human PTH. Variations of the cellular localization of the PCS or a complete depletion of the hormonal content, in all cells, were observed in eels made hypercalcemic by Ca overloading. The secretory activity of the two types of CS cells may be regulated by the plasma Ca2+ concentration.

[Are Stannius corpuscles the parathyroid glands of teleost fishes? Ultrastructural, cytologic and immunocytochemical arguments]. / Les corpuscules de Stannius sont-ils les glandes parathyroïdes des poissons téléostéens? Arguments ultrastructuraux, cytologiques et immunocytochimiques.

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.

[Immunocytochemical detection in Stannius corpuscles of the eel (Anguilla anguilla L.) of a hormone similar to the mammalian parathyroid hormone]. / Détection immunocytochimique dans les corpuscules de Stannius de l'anguille (Anguilla anguilla L.) d'une hormone proche de l'hormone parathyroïdienne mammalienne.

In eels the parathyrin of the corpuscles of Stannius (PCS), mammalian parathyroid-like hormone, has been localized in the cytoplasm of all the cells in the corpuscles. This detection was done by indirect immunofluorescence with an antiserum anti 1-84 bovine parathormone. The specificity of the reaction was demonstrated by inhibition of the coloration obtained with the 1-84 bovine parathormone and the active fragment 1-34 of human parathormone. Variations of the cellular localization of the PCS or a complete depletion of the hormonal content were observed in eels made hypercalcaemic by calcium overloading.

[Calcitonin in the ultimobrancial body of Anguilla (Anguilla anguilla L.): cytologic localization by indirect immunofluorescence using human anti-salmon-calcitonin antibodies]. / Calcitonine du corps ultimobranchial d'anguilles (Anguilla anguilla L.): localisation cytologique par immunofluorescence indirecte à l'aide d'un anticorps humain anti-calcitonine de saumon.

The localization of intracellular calcitonin has been achieved by immunofluorescence in the cytoplasm of all cells forming the epithelium of the ultimobranchial body of eels, using a human antiserum against synthetic Salmon calcitonin I. The specificity of the reaction is demonstrated by inhibition with synthetic salmon calcitonin (S.C.T.); the fluorescence is not inhibited by synthetic human calcitonin (H.C.T.).