title: Hypothyroidism changes adrenoceptor- and muscarinic receptor-mediated blood pressure responses.
abstract: Hypothyroidism was induced by the administration of 0.03% methimazole to drinking water for 1, 2 or 6 weeks to study whether there is a change in adrenoceptor- and muscarinic receptor-mediated blood pressure responses in hypothyroid rats. After 1, 2 and 6 weeks of treatment, the pressor response to norepinephrine was progressively suppressed, and after 6 weeks a significant suppression was observed as compared to control. The depressor response induced by isoprenaline, acetylcholine or sodium nitroprusside was not significantly different between control and hypothyroid rats at any time. The pressor response induced by N(G)-nitro-L-arginine (L-NOARG), an inhibitor of nitric oxide (NO) synthase, was significantly reduced in hypothyroid rats after 1, 2 or 6 weeks of treatment, and the magnitude of the reduction was almost the same for three groups. These results indicated that hypothyroidism causes a time-dependent decrease in pressor responses mediated by alpha-adrenoceptors, but a time-independent decrease in those induced by L-NOARG, and suggest that a progressive decrease in alpha-adrenoceptor-mediated pressor responses occurs in hypothyroidism; however, the decrease in basal NO production and/or release in the peripheral vasculature already occurs in hypothyroid rats at an early stage of the disease.
authors.affiliation: Second Department of Physiology, School of Medicine, Showa University, Hatanodai 1-5-8, Shinagawa-ku, Tokyo 142-8555, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Iwata
authors.forename: Hideo
authors.initials: H
authors.lastname: Honda
authors.forename: Hitomi
authors.initials: H
authors.lastname: Matsuda
authors.forename: Miwa
authors.initials: M
authors.lastname: Kondo
authors.forename: Jun
authors.initials: J
authors.lastname: Taniguchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Miwa
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kumasaka
authors.forename: Hiroko
authors.initials: H
authors.lastname: Moroe
authors.forename: Yoko
authors.initials: Y
authors.lastname: Notoya
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D007037:Hypothyroidism / Q000139:chemically induced / Q000503:physiopathology*; D008297:Male; D008713:Methimazole / Q000633:toxicity; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011941:Receptors, Adrenergic / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000502:physiology*
chemical_list: D011941:Receptors, Adrenergic; D011976:Receptors, Muscarinic; D008713:Methimazole; D009638:Norepinephrine