Luteal progesterone production and regulation in the viviparous dogfish, Squalus acanthias

• Published in: Journal of Experimental Zoology
• Main Authors: Tsang, Paul, Callard, Ian P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1987
• Subjects: spiny dogfish; Squalus acanthias
• Online Access: http://dx.doi.org/10.1002/jez.1402410313; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjez.1402410313; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jez.1402410313

Abstract Although vertebrate viviparity has evolved in parallel on several occasions, the endocrine function of the post‐ovulatory follicle (corpus luteum) is only well understood in eutherian mammals. In this report we present evidence that the corpus luteum is a phylogenetically ancient endocrine organ, which secretes progesterone in response to pituitary hormones in a representative of the oldest extant jawed vertebrate (the dogfish, Squalus acanthias ). Corpora lutea from pregnant aplacental viviparous spiny dogfish, Squalus acanthias , were removed, weighed and incubated in Eagle's Basal Medium supplemented with glutamine and urea for between 4 and 8 h at 18°C in 95% oxygen and 5% carbon dioxide. Corpora lutea decreased in weight from early to late pregnancy. Using radioisotopic methods, progesterone was definitively identified as a product of stage C corpora lutea. Basal progesterone synthesis, measured by radiommunoassay, increased from 301 ± 11.8 pg/mg/ corpus luteum/4 h in stage A of pregnancy to 1,881 ± 162.7 at stage B, and decreased markedly as corpora lutea decreased in size (stage C, 179 ± 19.2; stage D, 12 ± 3.2). An aqueous extract equivalent to one twenty‐fifth of the gonadotropic ventral lobe of the pituitary markedly stimulated progesterone in the incubates of stage C corpora lutea but not other stages. Corpus luteum function as an endocrine organ appears to be an ancient mechanism which antedates the appearance of terrestrial vertebrates.