Thymic proliferative response during different physiological states: A comparative study

O. A. Habbal*, I. M. McLean, M. F. Abu-Hijleh

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Objective-To study the thymic proliferative response during different physiological states to distinguish those changes due to alterations in steroid hormone secretion from those resulting from the presence of spermatozoa and/or early conceptual products in the female reproductive tract. Method-Using mature female rats of an inbred AO(RT1u) strain, observations on the thymus were made at 24 hour intervals during the oestrous cycle, early pseudopregnancy and early syngeneic pregnancy. Each daily group contained a minimum of 6 animals. Results-During the oestrous cycle, a significant mid-cycle increase of thymocyte proliferation occurred during dioestrus which peaked on day 2, and as a repetitive response may be a preparation for a coital challenge. This response may be oestrogen-dependent since oestrogen levels begin to increase during early dioestrus. The induction of pseudopregnancy generates a comparable but delayed increase in thymic proliferative activity. Since thymocyte proliferation and oestrogen secretion both peak on day 3 of pseudopregnancy, such a response may indeed also be oestrogen-dependent. After syngeneic mating, there was a significant depression in thymic proliferative activity on day 3 followed by a significant increase on day 5 compared with the same days of pseudopregnancy. Conclusion-This initial depression of proliferative activity may be induced by the immunosuppressive action of seminal plasma, to safeguard the preimplantation conceptus while the day 5 increase in cellular proliferation suggests a response to implantation.

Original languageEnglish
Pages (from-to)15-24
Number of pages10
JournalSultan Qaboos University Medical Journal
Issue number1
Publication statusPublished - Jan 2000


  • Implantation
  • Oestrous cycle
  • Pseudopregnancy
  • Seminal fluid
  • Thymus

ASJC Scopus subject areas

  • Medicine(all)


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