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The mammalian hypophysial pars tuberalis: a comparative immunocytochemical study.
General and Comparative Endocrinology
|November 1, 1984
Summary
The function of the pituitary pars tuberalis (PT) is unclear, but this study found gonadotropes and thyrotropes are common in mammals. However, many PT cells in some species remain unidentified, suggesting unknown functions.
Area of Science:
- Endocrinology
- Comparative Anatomy
- Cell Biology
Background:
- The function of the hypophysial pars tuberalis (PT), present in most vertebrates, remains largely unknown.
- Previous studies suggested hormone-containing cells exist in the PT, but comprehensive characterization across species was lacking.
Purpose of the Study:
- To characterize the secretory cell composition of the mammalian pituitary pars tuberalis (PT) using immunocytochemistry.
- To identify the types and distribution of hormone-producing cells within the PT across diverse mammalian species.
Main Methods:
- Immunocytochemistry was employed to analyze PT tissue from eight mammalian species: mouse, rat, guinea pig, rabbit, sheep, rhesus monkey, baboon, and human.
- A panel of 21 antisera targeting pituitary hormones including GH, PRL, ACTH, beta-endorphin, LH, FSH, and TSH was used to identify specific cell types.
Main Results:
- Gonadotropes were identified in the PT of all studied species and were the predominant cell type in humans, baboons, rhesus monkeys, sheep, guinea pigs, rabbits, and mice.
- Thyrotropes were detected in all species except sheep, being the predominant cell type in rats but less abundant than gonadotropes in others.
- While most PT cells were identified as gonadotropes or thyrotropes, a significant proportion of PT cells in rhesus monkeys, sheep, guinea pigs, rabbits, and mice did not react with any antisera, indicating their function is unknown.
Conclusions:
- The mammalian PT generally contains gonadotropes and thyrotropes, with other pituitary cell types being rare or absent.
- In humans, baboons, and rats, the majority of PT cells are identifiable, whereas in several other species, a substantial population of PT cells remains immunocytochemically uncharacterized, pointing to potential novel functions.
- The presence of follicles in the PT of most species, with non-reactive luminal contents, further suggests functions beyond the secretion of known adenohypophysial hormones.