We have examined the changes of intercellular electrical coupling protein connexin-43 (Cx43) and of PKC-ε in heart atria of diabetic rats and/or after the treatment with triiodothyronine (T3 ). Diabetes was induced in Wistar-Kyoto rats by streptozotocin (50 mg/kg, i.v.) and atria were examined after 5 (acute stage) and 10 (chronic stage) weeks. T 3 (10 μg/100 g/day) was applied via a gastric tube for the last 10 days prior to the end of the experiments to non-diabetic and to the half of diabetic rats. Expression and phosphorylated status of Cx43, as well as expression of PKC-ε , were analyzed by Western blots using mouse monoclonal anti-Cx43 and rabbit polyclonal anti-PKC-ε antibodies. We found that the Cx43 expression was significantly increased after the treatment with T3 and in the acute diabetes. Both in diabetes and after T3 treatment the phosphorylation of Cx43 isoforms was markedly suppressed compared to the non-diabetic and T3-untreated controls. Such a down-regulation was less pronounced in diabetic rats after the T3-treatment. The expression of atrial PKC-ε was increased in diabetic rats. This increase was suppressed after T3 administration and the expression was decreased in T3-treated non-diabetic rats. We suggest that the reduced Cx43 phosphorylation in diabetic and hyperthyroid rats can deteriorate a cell-to-cell coupling and consequently facilitate a development of atrial tachyarrhythmia in diabetic or hyperthyroid animals., M. Mitašíková ... [et al.]., and Obsahuje seznam literatury
We evaluated the effects of exercise on the vascular constrictor responses to α-adrenergic stimulation in the db/db mice. Twenty male db/db and their age-matched wild-type (WT) mice were exercised (1 hour/day, five days a week). Mice were anesthetized 7 weeks later, thoracic aortae were mounted in wire myograph and constrictor responses to phenylephrine (PE, 1 nM-10 μM) were obtained. Citrate synthase activity measured in the thigh adductor muscle was significantly increased in db/db mice that were exercise trained. Maximal force generated by PE was markedly greater in db/db aortae and exercise did not attenuate this augmented contractile response. Vessels were incubated with inhibitors of nitric oxide synthase (L-NAME, 200 μM), endothelin receptors (bosentan, 10 μM), protein kinase C (PKC) (calphostin C, 5 μM), cyclooxygenase (indomethacin, 10 μM) or Rho-kinase (Y-27632, 0.1 μM). Only calphostin-C normalized the augmented PE-induced constriction in db/db and db/db- exercised mice to that observed in WT (p<0.05). Cumulative additions of indolactam, a PKC activator, induced significantly greater constrictor responses in aortic rings of db/db mice compared to WT and exercise did not affect this response. Our data suggest that the augmented vasoconstriction observed in the aorta of db/db mice is likely due to increased PKC activity and that exercise do not ameliorate this increased PKC-mediated vasoconstriction., M. Khazaei, F. Moien-Afshari, T. J. Kieffer, I. Laher., and Obsahuje bibliografii a bibliiografické odkazy