GTP cyclohydrolase 1 inhibition attenuates vasodilation and increases blood pressure in rats

Brett M. Mitchell, Anne M. Dorrance, R. Clinton Webb

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


GTP cyclohydrolase 1 is the rate-limiting enzyme in production of tetrahydrobiopterin, a necessary cofactor for endothelial nitric oxide synthase. We tested the hypothesis that inhibition of tetrahydrobiopterin synthesis impairs endothelium-dependent relaxation and increase blood pressure in rats. 2,4-Diamino-6-hydroxypyrimidine (DAHP), a GTP cyclohydrolase 1 inhibitor, was given in drinking water (∼120 mg·kg-1·day -1) to male Sprague-Dawley rats for 3 days. Systolic blood pressures were measured (tail-cuff procedure) for 3 days before and each day during DAHP treatment. Blood pressure was significantly increased after DAHP treatment (122 ± 2 vs. 154 ± 3 mmHg before and after DAHP, respectively; P < 0.05). Endothelium-intact aortic segments from pentobarbital sodium-anesthetized rats were isolated and hung in organ chambers for measurement of isometric force generation. Aortas from DAHP-treated rats exhibited a decreased maximal relaxation to ACh compared with controls [% relaxation from phenylephrine (10-7 M)-induced contraction: DAHP 57 ± 6% vs. control 79 ± 4%; P < 0.65]. Relaxation responses to A-23187 were also decreased in aortas from DAHP-treated rats compared with controls. Incubation with sepiapterin (10-4 M, 1 h), which produces tetrahydrobiopterin via a salvage pathway, restored relaxation to ACh in aortas from DAHP-treated rats. Superoxide dismutase significantly increased ACh-induced relaxation in aortas from DAHP-treated rats, whereas catalase had no effect. Endothelium-independent relaxation to sodium nitroprusside in aortas from DAHP-treated rats was not different from control rats; however, nitric oxide synthase inhibition increased sensitivity to sodium nitroprusside in aortas from DAHP-treated rats. These results support the hypothesis that GTP cyclohydrolase 1 inhibition decreases relaxation and increases blood pressure in rats.

Original languageEnglish (US)
Pages (from-to)H2165-H2170
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number5 54-5
StatePublished - Nov 2003


  • Endothelium
  • Experimental hypertension
  • Nitric oxide synthase
  • Tetrahydrobiopterin

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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