{"title":"α - 1肾上腺素受体介导新生大鼠心肌细胞慢变性的研究","authors":"Hisakazu Kimura , Atsushi Miyamoto , Shin Kawana , Hideyo Ohshika","doi":"10.1016/0742-8413(93)90089-4","DOIUrl":null,"url":null,"abstract":"<div><p>1. In the present study, we investigated the effect of culture on <em>α</em><sub>1</sub>-adrenoceptors that mediate chronotropy and on <em>α</em><sub>1</sub>-adrenergic signal transduction in neonatal rat cardiac myocytes.</p><p>2. The spontaneous beating rate of neonatal rat myocytes after 3 or 7 days in culture was 37.4 ± 4.2 or 102.0 ± 4.3 beats min<sup>−</sup>, respectively. The <em>α</em><sub>1</sub>-adrenoceptor-mediated chronotropic effect of norepinephrine was positive at day 3 of culture. In contrast to day 3 of culture, the neonatal myocytes exhibited a negative chronotropic response to norepinephrine on day 7 of culture. Both of these effects of norepinephrine were completely abolished by prazosin.</p><p>3. The affinity (<em>K</em><sub>d</sub>) and/or density (<em>B</em><sub>max</sub>) of <em>α</em><sub>1</sub>-adrenoceptors labeled with [<sup>3</sup>H]prazosin in membranes from cultured myocytes were not significantly different between day 3 and day 7 of culture.</p><p>4. The expression of G<sub>s</sub>, G<sub>i</sub>, G<sub>q</sub> and G<sub>o</sub>, α-subunits in membranes from cultured myocytes was found to be significantly increased with the passage of culture time by immunoblot analysis. In contrast, no significant differences in G<sub>β</sub>-subunit expression were observed between day 3 and day 7 of culture.</p><p>5. Norepinephrine-stimulated inositol 1,4,5-trisphosphate production by radio-binding protein in neonatal myocytes after 7 days of culture was significantly higher than that of the day 3 counterpart.</p><p>6. No significant changes in phospholipid and cholesterol contents in membranes from neonatal myocytes were observed with longer culture times.</p><p>7. These results suggest that changes in the responsiveness to <em>α</em><sub>1</sub>-adrenergic stimulation from positive to negative chronotropy during culture of cardiac myocytes are mediated, at least in part, by functional alterations in the <em>α</em><sub>1</sub>-adrenergic signal transduction systems, including both G-protein expression and inositol 1,4,5-trisphosphate production.</p></div>","PeriodicalId":72650,"journal":{"name":"Comparative biochemistry and physiology. C: Comparative pharmacology","volume":"105 3","pages":"Pages 479-485"},"PeriodicalIF":0.0000,"publicationDate":"1993-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0742-8413(93)90089-4","citationCount":"8","resultStr":"{\"title\":\"Characterization of α1-adrenoceptors which mediate chronotropy in neonatal rat cardiac myocytes\",\"authors\":\"Hisakazu Kimura , Atsushi Miyamoto , Shin Kawana , Hideyo Ohshika\",\"doi\":\"10.1016/0742-8413(93)90089-4\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>1. In the present study, we investigated the effect of culture on <em>α</em><sub>1</sub>-adrenoceptors that mediate chronotropy and on <em>α</em><sub>1</sub>-adrenergic signal transduction in neonatal rat cardiac myocytes.</p><p>2. The spontaneous beating rate of neonatal rat myocytes after 3 or 7 days in culture was 37.4 ± 4.2 or 102.0 ± 4.3 beats min<sup>−</sup>, respectively. The <em>α</em><sub>1</sub>-adrenoceptor-mediated chronotropic effect of norepinephrine was positive at day 3 of culture. In contrast to day 3 of culture, the neonatal myocytes exhibited a negative chronotropic response to norepinephrine on day 7 of culture. Both of these effects of norepinephrine were completely abolished by prazosin.</p><p>3. The affinity (<em>K</em><sub>d</sub>) and/or density (<em>B</em><sub>max</sub>) of <em>α</em><sub>1</sub>-adrenoceptors labeled with [<sup>3</sup>H]prazosin in membranes from cultured myocytes were not significantly different between day 3 and day 7 of culture.</p><p>4. The expression of G<sub>s</sub>, G<sub>i</sub>, G<sub>q</sub> and G<sub>o</sub>, α-subunits in membranes from cultured myocytes was found to be significantly increased with the passage of culture time by immunoblot analysis. In contrast, no significant differences in G<sub>β</sub>-subunit expression were observed between day 3 and day 7 of culture.</p><p>5. Norepinephrine-stimulated inositol 1,4,5-trisphosphate production by radio-binding protein in neonatal myocytes after 7 days of culture was significantly higher than that of the day 3 counterpart.</p><p>6. No significant changes in phospholipid and cholesterol contents in membranes from neonatal myocytes were observed with longer culture times.</p><p>7. These results suggest that changes in the responsiveness to <em>α</em><sub>1</sub>-adrenergic stimulation from positive to negative chronotropy during culture of cardiac myocytes are mediated, at least in part, by functional alterations in the <em>α</em><sub>1</sub>-adrenergic signal transduction systems, including both G-protein expression and inositol 1,4,5-trisphosphate production.</p></div>\",\"PeriodicalId\":72650,\"journal\":{\"name\":\"Comparative biochemistry and physiology. 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C: Comparative pharmacology","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/0742841393900894","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
Characterization of α1-adrenoceptors which mediate chronotropy in neonatal rat cardiac myocytes
1. In the present study, we investigated the effect of culture on α1-adrenoceptors that mediate chronotropy and on α1-adrenergic signal transduction in neonatal rat cardiac myocytes.
2. The spontaneous beating rate of neonatal rat myocytes after 3 or 7 days in culture was 37.4 ± 4.2 or 102.0 ± 4.3 beats min−, respectively. The α1-adrenoceptor-mediated chronotropic effect of norepinephrine was positive at day 3 of culture. In contrast to day 3 of culture, the neonatal myocytes exhibited a negative chronotropic response to norepinephrine on day 7 of culture. Both of these effects of norepinephrine were completely abolished by prazosin.
3. The affinity (Kd) and/or density (Bmax) of α1-adrenoceptors labeled with [3H]prazosin in membranes from cultured myocytes were not significantly different between day 3 and day 7 of culture.
4. The expression of Gs, Gi, Gq and Go, α-subunits in membranes from cultured myocytes was found to be significantly increased with the passage of culture time by immunoblot analysis. In contrast, no significant differences in Gβ-subunit expression were observed between day 3 and day 7 of culture.
5. Norepinephrine-stimulated inositol 1,4,5-trisphosphate production by radio-binding protein in neonatal myocytes after 7 days of culture was significantly higher than that of the day 3 counterpart.
6. No significant changes in phospholipid and cholesterol contents in membranes from neonatal myocytes were observed with longer culture times.
7. These results suggest that changes in the responsiveness to α1-adrenergic stimulation from positive to negative chronotropy during culture of cardiac myocytes are mediated, at least in part, by functional alterations in the α1-adrenergic signal transduction systems, including both G-protein expression and inositol 1,4,5-trisphosphate production.
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