title: Correlation study of serum prolactin levels, pituitary weights, number and ultrastructure of pituitary lactotrophs in female Long-Evans rats.
abstract: Twenty-five female, 23-month-old Long-Evans rats were sacrificed for investigation of correlations between serum prolactin levels, pituitary weights, numbers and ultrastructural features of pituitary lactotrophs. Serum prolactin levels measured by radioimmunoassay varied from 7.1 ng/ml to 1,534.0 ng/ml. Pituitary weights ranged from 16.0 mg to 255.0 mg. Serum prolactin levels were increased when pituitary weights were high; statistical analysis revealed a correlation between the two. No significant correlation was evident between serum prolactin levels and lactotroph percentage and ultrastructure. Light microscopy revealed a large number of lactotrophs in almost every pituitary. Values for nuclear, cell and cytoplasmic areas, nuclear/cytoplasmic ratios and nucleolar diameters remained similar in the lactotrophs of all animals. Electron microscopy disclosed no lactotroph damage or vascular injury. Ultrastructural morphometry of lactotrophs in the pituitaries studied showed no major differences in cytoplasmic volume densities of endoplasmic reticulum, Golgi complex, mitochondria, secretory granules and lysosomes as well as secretory granule diameters. It is reasonable to conclude that elevations of serum prolactin levels are due to an increase in pituitary mass, resulting from accumulation of lactotrophs. Thus hyperprolactinemia appears to be secondary to an increase in the number of lactotrophs and not hyperactivity of individual cells.
authors.affiliation: Department of Pathology, St. Michael's Hospital, University of Toronto, Ontario, Canada.
authors.forename: R E
authors.initials: RE
authors.lastname: Baird
authors.forename: N E
authors.initials: NE
authors.lastname: Losinski
authors.forename: K
authors.initials: K
authors.lastname: Kovacs
authors.forename: M O
authors.initials: MO
authors.lastname: Thorner
mesh_terms: D000818:Animals; D002452:Cell Count; D005260:Female; D008854:Microscopy, Electron; D009929:Organ Size; D015388:Organelles / Q000648:ultrastructure; D010903:Pituitary Gland, Anterior / Q000033:anatomy & histology* / Q000166:cytology / Q000648:ultrastructure; D011388:Prolactin / Q000097:blood*; D051381:Rats; D013223:Statistics as Topic
chemical_list: D011388:Prolactin