Follistatin concentrations in male sheep increase following sham castration/castration or injection of interleukin-1 beta.

Plasma follistatin (FS) concentrations were determined after castration (n = 5) or sham castration (n = 4) of mature rams. Both treatments resulted in a prolonged increase in FS between 7 and 19 h after surgery, which returned to pretreatment concentrations by 24 h. Tumour necrosis factor-alpha (TNF-alpha), a sensitive maker of an acute-phase response, was undetectable in plasma, indicating that the FS response was not induced by trauma due to surgery. In a second experiment, injection of castrated rams (n = 4) with ovine recombinant interleukin-1 beta, an acute-phase mediator, resulted in a sustained rise in FS concentrations within 4 h of injection. Plasma TNF-alpha concentrations increased transiently within 1 h of interleukin-1 beta injection, indicating that an acute-phase response had been initiated. Plasma follicle-stimulating hormone (FSH) concentrations were significantly decreased at 8 and 24 h after interleukin-1 beta injection, strongly suggestive of an inhibitory effect of increased FS concentrations on the secretion of FSH. Injection of castrated rams (n = 2) with a control preparation of recombinant interleukin-2 did not induce an acute-phase response, and plasma FS and FSH concentrations were unaffected. These data show that the testis is not a major source of circulating FS, that the increase in circulating FS following sham castration/castration is not due to an acute-phase response, but that conversely FS concentrations are modulated by the acute-phase mediator, interleukin-1 beta.