Effects of oral propylthiouracil treatment on nitric oxide production in rat aorta

The effects of oral propylthiouracil (PTU) treatment on vascular nitric oxide (NO) production were studied in the rat aorta. Rats were fed a standard low fat diet with or without 0.1% PTU, for 2 or 4 weeks, or for 2 weeks with additional thyroxine injections. Concentration response curves were then constructed to phenylephrine (PE) in both endothelium‐intact and denuded aortic rings from these animals and after incubation with 0.1 mM L‐NGnitroarginine (L‐NOARG). In addition, expression of nitric oxide synthase (NOS) was analysed in sections of aorta from PTU‐treated and control rats using rabbit polyclonal antibodies to both inducible NOS (iNOS) and endothelial NOS (eNOS). Oral PTU treatment resulted in a significant reduction in both the maximum response (control, 0.53±0.02; 2 week PTU, 0.20±0.07; 4 week PTU, 0.07±0.02 g mg−1) and vessel sensitivity (EC50 values: control, 9.10×10−8±0.67; 2 week PTU, 7.45×10−7±1.15; 4 week PTU, 9.73×10−7±0.45 M) to PE in endothelium‐intact vessel rings, as compared to controls (P