The influence of TSH and ACTH on purine and pteridine deposition in the skin of rainbow trout (Salmo gairdneri)

The specific activities (s.a.) and levels of skin purines and pteridines were determined in 1-year-old rainbow trout that were injected with [14C]glycine and treated for 20–28 days with bovine thyroid-stimulating hormone (TSH) or adrenocorticotropic hormone (ACTH). TSH increased significantly the s.a. and levels of guanine and hypoxanthine, but had no effect on these parameters for guanosine monophosphate (GMP), biopterin, 2-amino-4-hydroxypteridine (AHP), and ichthyopterin. The s.a. of isoxanthopterin (IXP) was significantly decreased. ACTH increased significantly the s.a. and levels of GMP, biopterin, AHP, IXP, and ichthyopterin. The s.a. and levels of guanine and hypoxanthine were not altered significantly. Thus TSH promotes purine synthesis with no significant change in the synthesis of most pteridines, while ACTH promotes pteridine synthesis with no significant change in purine synthesis. These observations on trout skin do not favour a previously advanced generalization that purine and pteridine biosynthetic pathways compete for a common substrate.