title: Ultrastructural characteristics of two distinct gonadotropes (GTH I- and GTH II-cells) in the pituitary of rainbow trout Oncorhynchus mykiss.
abstract: The salmonid pituitary produces two chemically distinct gonadotropins (GTHI and GTHII). Ultrastructural characteristics of GTHI- and GTHII-producing cells were studied in the trout pituitary with electronmicroscopic immunocytochemistry using antisera against salmon GTHIβ- and IIβ-subunits. In pituitaries from vitellogenic fish, GTHI-cells were characterized by numerous dilated cisternae of the granular endoplasmic reticulum (GER) and a small number of Iβ-positive granules (diameter, 100-300 nm), whereas GTHIIβ-immunoreactivity was found on granules (diameter, 200-400 nm) and large globules (diameter, 500-4000 nm) in apparently different cells (GTHII-cells). Distinct cellular distributions of GTHI and GTHII were maintained during gametogenesis, although morphological characteristics of GTHI- and GTHII-cells overlapped each other due to changes in number and size of the granules, globules and cisternae of the GER. Interestingly, the globules in the GTHI-cells were immunonegative for GTHIβ, although in the GTHII-cells they were always stained with GTHIIβ-antiserum. These results confirm that GTHIβ and GTHIIβ are synthesized in distinctly different cell-types in the salmonid pituitary and indicate that morphological characteristics cannot be used to distinguish these two cell-types.
authors.affiliation: Department of Anatomy, Showa University School of Medicine, Tokyo, 142, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Naito
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.forename: M
authors.initials: M
authors.lastname: Nozaki
authors.forename: P
authors.initials: P
authors.lastname: Swanson
authors.forename: H
authors.initials: H
authors.lastname: Kawauchi
authors.forename: Y
authors.initials: Y
authors.lastname: Nakai