The secretory pattern and source of immunoreactive prolactin in pregnant African (Loxodonta africana) and Asian (Elephas maximus) elephants

Yuki Yamamoto, Tatsuya Yamamoto, Natsuki Yuto, Thomas B. Hildebrandt, Imke Lueders, Gudrun Wibbelt, Osamu Shiina, Yasushi Mouri, Keisuke Sugimura, Sayuri Sakamoto, Saroch Kaewmanee, Kentaro Nagaoka, Gen Watanabe, Kazuyoshi Taya

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


The objective of the present study was to define the secretion of prolactin (PRL) in pregnant African and Asian elephants. Levels of immunoreactive (ir-) PRL in serum and placental homogenates were measured by a heterologous radioimmunoassay (RIA) based on an ovine and human RIA system, and the localization of ir-PRL in the placenta was detected by immunohistochemistry using anti-human PRL. Circulating ir-PRL clearly showed a biphasic pattern during pregnancy in African and Asian elephants. Serum levels of ir-PRL started to increase from the 4 - 6th month of gestation and reached the first peak level around the 11-14th month. A second peak of circulating ir-PRL levels was observed around the 18-20th month of gestation followed by an abrupt decline after parturition. In contrast, in a case of abortion of an African elephant, the second peak of ir-PRL was not observed, and the levels remained low for about four months until parturition. The weight of the fetus delivered at the 17th month of gestation was 23.5 kg, which was quite small compared with normal fetuses in previous reports. Ir-PRL was detected in placental homogenates, and immunolocalization was observed in trophoblasts in both the African and Asian elephants, indicating that the placenta is the source of ir-PRL during pregnancy in elephants. The present results clearly demonstrated that circulating ir-PRL shows a biphasic pattern during normal pregnancy and that the placenta appears to be an important source of circulating ir-PRL during pregnancy in both African and Asian elephants.

Original languageEnglish
Pages (from-to)105-111
Number of pages7
JournalJournal of Reproduction and Development
Issue number1
Publication statusPublished - 2012
Externally publishedYes


  • Female elephant
  • Fetal growth
  • Placenta
  • Pregnancy
  • Prolactin

ASJC Scopus subject areas

  • Animal Science and Zoology


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