We aimed to study the impact of altered thyroid status on myocardial expression of electrical coupling protein connexin-43 (Cx43), the susceptibility of rats to ventricular fibrillation (VF) and the effects of antioxidant-rich red palm oil (RPO). Adult male and female euthyroid, hyperthyroid (treated with T3/T4), hypothyroid (treated with methimazole) Wistar rats supplemented or not with RPO for 6 weeks were used. Function of isolated perfused heart and VF threshold were determined. Left ventricular tissue was used for assessment of mRNA and protein levels of Cx43, its phosphorylated forms and topology. Protein kinase C signaling (PKC) and gene transcripts of some proteins related to cardiac arrhythmias were assessed. Hyperthyroid state resulted in decrease of total and phosphorylated forms of Cx43 and suppression of PKC-ε expression in males and females, decrease of Cx43 mRNA in females, decrease of VF threshold and increase of functional parameters in male rat hearts. In contrast, hypothyroid status resulted in the increase of total and phosphorylated forms of Cx43, enhancement PKC-ε expression in males and females, increase of Cx43 mRNA in females, increase of VF threshold and decrease of functional parameters in male rat hearts. Function of the heart was partially normalized by RPO intake, which also enhanced myocardial Cx43 and PKC-ε expression as well as increased VF threshold in hyperthyroid male rats. We conclude that there is an inverse relationship between myocardial expression of Cx43, including its functional phosphorylated forms, and susceptibility of male rat hearts to VF in condition of altered thyroid status. RPO intake partly ameliorated adverse changes caused by excess of thyroid hormones.

• Klíčová slova
• Cardiac arrhythmias, Connexin-43, PKC, Red palm oil, Thyroid hormones,
• MeSH
• aplikace orální MeSH
• konexin 43 antagonisté a inhibitory   genetika   metabolismus   MeSH
• krysa rodu Rattus MeSH
• messenger RNA antagonisté a inhibitory   genetika   metabolismus   MeSH
• myokard metabolismus   MeSH
• oleje rostlin aplikace a dávkování   farmakologie   MeSH
• palmový olej MeSH
• potkani Wistar MeSH
• srdce účinky léků   MeSH
• srdeční arytmie farmakoterapie   metabolismus   MeSH
• štítná žláza účinky léků   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• Gja1 protein, rat MeSH Prohlížeč
• konexin 43 MeSH
• messenger RNA MeSH
• oleje rostlin MeSH
• palmový olej MeSH

In this mini-review, we briefly present the data regarding the effect of extrinsic factors, i.e., innervation and thyroid hormones (TH) on myosin heavy chain genes and isoforms expression and consequently on muscle fiber type transitions. It has been well known that reduced neuromuscular activity, hyperthyroidism or mechanical unloading stimulate slow-to-fast fiber type transitions, while increased neuromuscular activity, hypothyroidism and higher mechanical loading result in fast to slow fiber type transitions. As there is a plethora of results on these topics, we focus mostly on data relevant to our experimental model of slow-to-fast muscle transformation following heterochronous intramuscular isotransplantation in rats with altered TH status.

• MeSH
• hormony štítné žlázy metabolismus   farmakologie   MeSH
• krysa rodu Rattus MeSH
• protein - isoformy metabolismus   MeSH
• regulace genové exprese účinky léků   fyziologie   MeSH
• těžké řetězce myosinu genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• hormony štítné žlázy MeSH
• protein - isoformy MeSH
• těžké řetězce myosinu MeSH

We studied the effect of regeneration, altered innervation and thyroid hormone (TH) levels on fiber type transitions in slow soleus (SOL) muscles grafted (GRAFT) into host extensor digitorum longus (EDLh) muscles of euthyroid (EU), hyperthyroid (HT) and hypothyroid (HY) Lewis strain rats. SOL muscles were excised from 3-week to 4-week-old inbred Lewis rats and intramuscularly transplanted into EDLh muscles of 2-month-old female rats of the same strain. The proportions of type 1, 2A, 2X and 2B fibers of GRAFT were determined by immunohistochemistry and compared with those of EDLh muscle and EDL and SOL muscles of the unoperated contralateral hind limb. After an average regeneration period of 6-7 months and after being reinnervated by the "fast" peroneal nerve of EDLh muscle, GRAFT was transformed into a fast muscle. However, the extent of GRAFT transformation varied with different TH states. In the EU rats, GRAFT contained about 95 % of fast fibers, among which type 2X and 2B fibers predominated (about 75 %). The transition toward fast muscle phenotype was more pronounced in HT status, where the fastest type 2B fibers predominated. On the contrary, in HY status, the slow to fast transformation was less pronounced, as GRAFT contained less type 2B and 2X but more type 2A and 1 fibers. We conclude that the type of innervation is the crucial factor for the slow to fast fiber type transitions in GRAFT, but the extent of muscle transformation is further modulated by altered TH status.

• MeSH
• časové faktory MeSH
• hormony štítné žlázy chemie   metabolismus   MeSH
• kosterní svaly cytologie   metabolismus   transplantace   MeSH
• krysa rodu Rattus MeSH
• potkani inbrední LEW MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• hormony štítné žlázy MeSH