Thymosin fraction 5 causes increased serum corticosterone in rodents in vivo.
McGillis. J P JP; Hall. N R NR; Vahouny. G V GV; Goldstein. A L AL
Key Findings
- Thymosin fraction 5 raises serum corticosterone in a dose‑dependent way in rodents
- Thymosin‑alpha‑1 alone does not affect corticosterone up to 100 µg dose
- The corticosterone increase only occurs when baseline levels are below ~80 ng/ml
Practical Outcomes
- If you’re using thymosin‑alpha‑1, you don’t need to worry about it spiking stress hormones. Avoid using crude thymosin fraction 5 if you want to keep cortisol-like hormones low, especially when your baseline stress hormone levels are already low.
Summary
Injecting the mixed peptide blend called thymosin fraction 5 makes stress hormone (corticosterone) go up in mice and rats, but the pure 28‑amino‑acid peptide thymosin‑alpha‑1 does not, even at high doses. The hormone boost only happens when the animal’s baseline levels are low.
Abstract
In these studies it was found that i.p. injection of thymosin fraction 5 (TF5) caused a dose-dependent increase in serum corticosterone in male Swiss Webster mice and in male Wistar rats. The maximum responses were seen at 1 and 2 hr, respectively. There was no effect on serum corticosterone in mice when Thymosin alpha 1 (a 28 amino acid peptide isolated from TF5) was injected i.p. at doses up to 100 micrograms. The steroidogenic effects of TF5 were seen only when the basal levels of serum corticosterone were low (less than 80 ng/ml). In studies in which the baseline levels in the animal colony were elevated (greater than 80 ng/ml), there were no steroidogenic effects, or they were minimal. These results suggest that some component of TF5 may influence pituitary adrenal function.
Study Information
pubmed
1985