Immunomodulation by testosterone and corticosterone in toads: Experimental evidences from transdermal application

Area of Science:

• Comparative immunology
• Endocrinology
• Amphibian physiology

Background:

• Androgens and glucocorticoids are vital for vertebrate reproduction and immune function.
• In anurans, testosterone and corticosterone influence sexual behavior, reproduction, and immunity.

Purpose of the Study:

• To investigate the immunomodulatory effects of acute testosterone and corticosterone administration in male toads (Rhinella jimi).
• To assess the impact of these hormones on plasma bacterial killing ability and phytohemagglutinin-induced swelling response.

Main Methods:

• Male toads were treated with transdermal doses of testosterone (T) and corticosterone (CORT).
• Immune variables measured included plasma bacterial killing ability (BKA) and phytohemagglutinin (PHA) swelling response.
• Plasma hormone levels (T-DHT, CORT) were measured 1 hour post-treatment.

Main Results:

• Transdermal T and CORT increased plasma levels of respective hormones without dose-specific effects.
• Testosterone treatment did not alter BKA or PHA swelling response.
• Corticosterone treatment led to an earlier maximum PHA swelling response and a trend towards lower BKA.

Conclusions:

• Acute elevation of plasma corticosterone levels in male toads accelerates inflammatory resolution.
• Corticosterone suppresses non-cellular innate immune responses, impacting immune function in anurans.
• Testosterone does not appear to significantly modulate these specific innate immune parameters in this study.