Opioid peptides mediate heat stress-induced immunosuppression during pregnancy

Hiroyuki Nakamura, Hirofumi Nagase, Masami Yoshida, Keiki Ogino, Toshio Seto, Kotaro Hatta, Ichiyo Matsuzaki

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


To clarify the involvement of the opioid system in enhanced immunosuppression induced by heat stress during pregnancy, we examined the effects of heat exposure and intraperitoneal administration of opioid receptor antagonist naloxone on β-endorphin (β-EP) in blood, pituitary lobes, and placenta as well as splenic natural killer cell activity (NKCA) and placental steroids in pregnant rats at 15-16 days gestation. Two-way analysis of variance revealed significant increases in blood β-EP induced by heat and naloxone and a significant interaction between heat and naloxone on blood β-EP and progesterone (P). Whereas heat reduced NKCA, intraperitoneal administration of naloxone reversed it. Significant increases in blood and placental β-EP induced by both heat and naloxone administration and a significant interaction on blood and placental β-EP was observed. These results suggest that immunosuppression produced by heat stress during pregnancy is mediated by the opioid system. A positive correlation between β-EP in blood and placenta during heat and naloxone administration suggests that increased placental β-EP during heat results in hypersecretion of β- EP into blood. P increased by heat during pregnancy may be involved in the immunosuppression.

Original languageEnglish
Pages (from-to)R672-R676
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number3 43-3
Publication statusPublished - Mar 1998
Externally publishedYes


  • Natural killer cell activity
  • Pituitary
  • Placenta
  • Progesterone
  • β-Endorphin

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


Dive into the research topics of 'Opioid peptides mediate heat stress-induced immunosuppression during pregnancy'. Together they form a unique fingerprint.

Cite this