Effects of acute and chronic corticosterone treatments in the American Bullfrog wound healing

Glucocorticoid (GC) release is triggered by adverse stimuli that activate hypothalamus-pituitary-adrenal/interrenal (HPA/I) axis. Glucocorticoids may enhance or suppress immune functions depending on the level of elevation. In this study, we investigated the effects of transient and chronic increases of CORT on the wound healing of the American bullfrog. Frogs were submitted to a daily transdermal hormonal application that acutely elevated CORT plasma levels, or vehicle as a control. Other frogs were surgically implanted with a silastic tube filled with CORT that resulted in chronic elevation of CORT plasma levels or received empty implants as a control. A dermal biopsy was performed to create a wound and was photographed every 3 days. Individuals treated with transdermal CORT started healing faster than their control 32 days after the biopsy. Frogs that received CORT implants tended to heal slower than control subjects. Plasma bacterial killing ability (BKA) was not affected by treatme..., Animal maintenance and experimental groups
Forty adult male American bullfrogs (Lithobates catesbeianus) were bought from a local animal farm in the state of São Paulo, Brazil (Ranário Santa Clara, Santa Isabel, SP – 23°18’13.0”S 46°12’21.5”W) and brought into laboratory conditions at the University of São Paulo in October 2017 (Week 0). Animals were kept in individual plastic boxes (43.0 x 28.5 x 26.5 cm) inside a climatic chamber (FITOTRON 011 – Eletro-lab, São Paulo/SP/Brazil) with controlled photoperiod (12:12 LD, lights on 6 a.m.) and temperature (22±0.5°C.) Each individual box was equipped with a small container with water, and animals were weekly fed with 10 cockroaches (Nauphoeta cinerea). Seven days of habituation were given before experiments began.
Animals were weighed (0.01g) and had their snout-vent length (SVL) measured (0.01mm). Animals were randomly separated into four different groups of 10 animals each: 1) Transdermal application of CORT solution, 2) Transdermal applic...,