Gonadotropin production and release in female goldfish (Carassius auratus) after administration of pimozide and an LHRH analogue as studied by electron microscopy and radioimmunoassay

Functional changes of the LH-immunoreactive cells in adenohypophysis of the common carp (Cyprinus carpio) from rivers contaminated with estrogenic chemicals

The adverse effect of estrogenic chemicals on luteinizing hormone-immunoreactive (LH-ir) cells in the adenohypophysis of common carp (Cyprinus carpio) was examined using immunocytochemical and morphometric methods. Adult male fish were collected from two contaminated sites (Ishizu and Wada Rivers) and from a control pond at Agriculture, Food and Environmental Sciences, Research Center of Osaka Prefecture. The concentration of nonylphenol, bisphenol A and 17beta-estradiol in the Ishizu River was 3-4 times higher than that in the Wada River. The proportion and size of LH-ir cells were evaluated using the point-counting method by optical microscopy. In control carp, the proportion of LH-ir cells in the breeding season was significantly lower than in the pre- and post-breeding seasons. The same tendency was also found in Ishizu and Wada River carp, but without statistical significance. The proportion of LH-ir cells in Ishizu River carp was significantly lower than that of the control and the Wada River in all seasons. The LH-ir cells in control carp increased in size in the breeding season. LH-ir cells in Ishizu River carp were significantly (p<0.05) smaller than those in control fish, but not different from Wada River carp. A disturbance in the secretory function of LH-ir cells was found in carp from the Ishizu River; granulation and vacuolation were not in synchronization with those of control and Wada River fish. Our data suggest that the estrogenic chemicals in the Ishizu River interfere with functions of LH-ir cells directly or through the testis.

Investigation into the duality of gonadotropic cells of Mediterranean yellowtail (Seriola dumerilii, Risso 1810): immunocytochemical and ultrastructural studies

Two antisera against the follicle-stimulating hormone-like gonadotropin (FSH) of Mediterranean (M.) yellowtail, anti-My FSHa and anti-My FSHb, were obtained. Anti-My FSHa serum specifically recognized FSH cells and did not react with any other pituitary cell type, while anti-My FSHb serum recognized the alpha-subunit of the pituitary glycoprotein hormones and immunostained FSH, luteinizing hormone-like gonadotropin (LH), and thyrotropin (TSH) cells. Anti-My FSHa serum, together with a previously obtained anti-My LHbeta serum, were used to further investigate the duality of gonadotropic cells in M. yellowtail by light and electron microscopic immunocytochemistry; three immunologically different gonadotropic cell populations expressing FSH, LH, or both hormones, were revealed. The three cell populations had the same regional distribution in the pituitary gland: the proximal pars distalis, including the thin ring surrounding the pars intermedia. However, while FSH cells were found isolated or forming small clusters, LH cells formed strands or compact groups, and were more numerous than FSH cells. FSH/LH cells were scarce. At the ultrastructural level, vesicular, granular, and intermediate FSH, LH, and FSH/LH cells were found; secretory granules and globules, on the one hand, or conspicuous dilated cisternae of rough endoplasmic reticulum (or both) predominated, respectively, in these cell types. The production of either FSH or LH, or both hormones, was not reflected in the ultrastructural features of gonadotropic cells. Thus, a single morphological cell type of varying ultrastructure depending on the functional stage seemed to encompass all gonadotropic cells in M. yellowtail. All forms of FSH, LH, and FSH/LH cells were found in involution.

Gonadotropic and thyrotropic cells from the Mediterranean yellowtail (Seriola dumerilii; Risso, 1810): immunocytochemical and ultrastructural characterization

BACKGROUND

Gonadotropins GTH I and GTH II from the pituitary of Mediterranean (M.) yellowtail (Seriola dumerilii) were isolated and characterized, and antisera to the whole GTH II molecule (anti-My alpha,betaGTH II) and to its beta-subunit (anti-My betaGTH II) were obtained. At the light microscopic level, anti-My alpha,betaGTH II reacted with My betaGTH II-immunoreactive cells (GTH II cells), thyroid-stimulating hormone (TSH) cells, and a third cell population, which could have been GTH I cells. The aim of this study was the ultrastructural characterization of GTH and TSH cells in M. yellowtail using the immunogold method in order to provide a basis for future research into reproduction of this species.

METHODS

Pituitaries from mature male and female specimens reared in captivity were dissected out and processed for electron microscopy. The immunogold method was carried out by using anti-My alpha,betaGTH II, anti-My alpha,betaGTH II preabsorbed with the alpha subunit of the M. yellowtail GTH (My alphaGTH-subunit), anti-My betaGTH II, anti-human (h) alpha,betaTSH, and anti-h betaTSH sera to reveal gonadotropic and thyrotropic cells.

RESULTS

M. yellowtail gonadotropic cells were very heterogeneous with regard to their size, shape, and ultrastructural features. Cells were found with numerous, round, variably electron-dense, secretory granules and globules; others were found with their cytoplasm occupied mostly by dilated cisternae of rough endoplasmic reticulum (RER) and scarce secretory granules; and other intermediate cell forms were found that showed varying proportions of secretory granules and dilated RER. The secretory granules and globules were immunogold labeled with anti-My alpha,betaGTH II, and the reaction was weaker in the latter. A similar immunogold-labeling pattern was found with anti-My betaGTH II and with anti-My alpha,betaGTH II preabsorbed with the My alphaGTH-subunit, although some cells that showed the same ultrastructural features described above were not immunogold labeled and could have been GTH I cells. Thyrotropic cells had small, round, secretory granules of medium or high electron density that were immunogold labeled with anti-My alpha,betaGTH II, anti-h alpha,betaTSH, and anti-h betaTSH sera, but not with anti-My betaGTH II or anti-My alpha,betaGTH II serum preabsorbed with the My alphaGTH-subunit. All of the cell forms described for gonadotropes and thyrotropes were also found in a state of involution.

CONCLUSIONS

Gonadotropes that are of a single morphological type but that vary in ultrastructure are present in the pituitary of captive M. yellowtail. GTH II- and putative GTH I-producing cells were distinguishable from one another and from TSH cells by their different reactions to anti-My alpha,betaGTH II, anti-My betaGTH II, and anti-My alpha,betaGTH II preabsorbed with the My alphaGTH-subunit.

Stereological study of gonadotropes in the frog, Rana pipiens, after GnRH stimulation in vitro

Previous physiological results have indicated the existence of two releasable pools of gonadotropins in amphibian pituitaries: an acute releasable pool that appears independent of protein synthesis, and a storage pool involved in chronic release that depends on protein synthesis. To elucidate the ultrastructural localization of these pools and the morphological changes induced in gonadotrope cells after treatment with gonadotropin-releasing hormone, we carried out a morphometric study of immuno-identified gonadotrope cells using an in vitro superfusion system. Treatment with gonadotropin-releasing hormone induced a degranulation of small (110-255 nm) and medium (236-360 nm) secretory granules as well as hypertrophy of the endoplasmic reticulum and Golgi complex. Simultaneous incubation with gonadotropin-releasing hormone and cycloheximide inhibited the release of secretory granules although the endoplasmic reticulum and Golgi complex were hypertrophied. These morphological results strongly suggest: (1) that gonadotropin-releasing hormone induces degranulation and hypertrophy of the biosynthetic machinery in gonadotrope cells; and (2) that the activation of the endoplasmic reticulum and Golgi complex by stimulation with gonadotropin-releasing hormone is independent of protein synthesis, while the release of secretory granules is protein synthesis-dependent. In addition, the second or "storage" pool of gonadotropin is associated mainly with the small and medium secretory granules.

Isolation and characterization of carp prolactin

Prolactin (PRL) was extracted with acid-acetone from common carp (Cyprinus carpio) pituitary glands and purified by gel filtration on Sephadex G-75, ion-exchange chromatography on DEAE-cellulose, and reversed-phase high-performance liquid chromatography (HPLC) on TSK-gel TMS 250 with a yield of 0.7 mg/g wet tissue. At each stage of purification, fractions were monitored by HPLC on TSK-gel ODS 120T and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Carp PRL was almost equipotent with ovine PRL in retaining plasma Na concentrations in the hypophysectomized killifish, Fundulus heteroclitus. Immunocytochemistry at both the light and electron microscopic levels revealed that carp PRL antiserum specifically stained cells in the goldfish rostral pars distalis. No cross reaction with putative growth hormone (GH) cells in the proximal pars distalis was observed. The specificity of the carp PRL antiserum was confirmed by immunoblot studies. Although immunostaining of both carp and salmon PRL was observed, there was no cross reaction to GHs from these species. Carp PRL had a sole N-terminal residue of valine, a molecular weight of 23 kDa in SDS-PAGE, and an isoelectric point of 7.3 by gel electrofocusing. Based on these results, together with the knowledge of physicochemical properties of salmon and tilapia PRLs, we propose a standard procedure for isolation of fish PRLs.