In the present paper we describe changes of anatomical parameters in inbred Lewis strain rats, namely their body weight, body weight gain per week, absolute and relative heart, thyroid gland and skeletal muscle weights, that are assumed to reflect experimentally altered thyroid status. The hyperthyroid state was induced by DL-thyroxine or Na 3,3',5-triiodo-L-thyronine, while methimazole was employed for inducing hypothyroidism. We have found that when compared to euthyroid rats, hypothyroidism resulted in a significantly lower body weight gain, absolute and relative heart weight and, in contrast, in a significant increase of absolute and relative thyroid gland weight. On the other hand, hyperthyroidism led to a significant increase of absolute and relative heart weight and to a significant reduction of absolute and relative thyroid gland weight. However, the body mass was not significantly altered in hyperthyroidism as compared with euthyroid rats. We conclude that our protocol leads to chronic hyper- or hypothyroidism as demonstrated by body, heart and thyroid gland weight changes. These anatomical data can thus be utilized as supplemental criteria for the assessment of the thyroid state of experimental rats., T. Soukup, G. Zachařová, V. Smerdu, I. Jirmanová., and Obsahuje bibliografii
We developed a new method for the quantitative determination of myosin heavy chain (MyHC) isoforms taking advantage of immunochemical differences and based on the ELISA principle. In the present paper we compare anal ysis of MyHC isoforms using the SDS-PAGE and the ELISA methods in the same samples of adult female inbred Lewis strain euthyroid, hyperthyroid and hypothyroid rats. In all thyroid states, the same composition and corresponding changes of MyHC isoforms were determined using both methodological approaches in the slow soleus and the fast extensor digitorum longus muscles. Our results showed that ELISA can be used for a “semi-quantitative” or “comparative” measurement of MyHC isoforms in multiple muscle samples, but that it is neither more exact no r faster compared to SDS-PAGE., Jan Říčný., and Obsahuje bibliografii a bibliografické odkazy
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 have analyzed the influence of altered thyroid hormone levels on changes of MyHC protein isoforms and their mRNA transcripts in the soleus muscle of 2-, 4- and 7-month-old euthyroid (EU), hypothyroid (HY) and hyperthyroid (TH) female inbred Lewis strain rats (methimazole and T3 treatment started 3 to 4 weeks after birth). We have found that the content of the dominant MyHC 1 isoform gradually increased in the EU rats and that this increase was more progressive in the HY rats at all three stages. On the other hand, in the TH rats the content of MyHC 1 isoform was the highest in the 2-month-old rats and it decreased with an increasing length of T3 treatment. The content of the minor 2a MyHC isoform followed the opposite pattern. In contrast to the protein isoforms, the MyHC mRNA transcripts remained at similar levels. Nevertheless, in general, the MyHC 1 mRNA level was decreased and MyHC 2a transcript increased in the TH rats, while the opposite changes occurred in the HY rats. Our results thus suggest that in the rat soleus muscle, both increased and decreased levels of thyroid hormones speed up the formation of an adult slow phenotype which is demonstrated by the precocious appearance of the slow MyHC 1 isoform, but opposite to the hypothyroid status, a longer T3 application promotes the expression of the faster MyHC 2a isoform., A. Vadászová-Soukup, T. Soukup., and Obsahuje bibliografii a bibliografické odkazy
a1_We analyzed fiber type composition of soleus and extensor digitorum longus (EDL) muscles of 3- to 19-month-old male and female inbred Lewis rats using histochemical demonstration of mATPase activity. The rats were divided into four groups of the mean age of 3, 6, 9 and 14 months. We found that the soleus muscle of 3-month-old rats contained significantly more of fast 2A fibers and less of slow type 1 fibers compared to older rats, while no significant difference was found between female and male rats at any age group. In contrast, we found no significant difference in the EDL fiber type composition among the age groups, but we found that the EDL muscle of female rats contained significantly less 2A fibers and more 2B fibers than that of male animals. Our results thus revealed an age difference in the soleus muscle and a sex difference in the EDL muscle among postnatal Lewis rats. The number of slow type 1 fibers in the soleus muscle varied between 87 and 100 % and that of 2A fibers between 13 and 0 %. In the EDL the percentage of type 1 fibers varied between 2.6 and 8.7 %, that of 2A fibers between 12.6 and 25.8 % and that of 2B fibers between 70.4 and 81.6 %. Both muscles thus exhibited a considerable degree of variability among individual animals even in the same age group. Furthermore, a comparison of the Lewis rats with literature data of other rat strains showed that the number of fast 2A fibers in the soleus muscle of 4-month-old and older animals decreased in this order: SHR > Lister Hooded > Fisher 344 > Sprague- Dawley > Wistar > WBN/Kob > Lewis strain, being almost 20 % in the SHR and less than 2 % in the Lewis rats. In contrast, the “fastest” composition (judged according to the percentage of the fastest 2B fibers) of the EDL muscle was demonstrated by Lewis, Wistar and Fisher 344 rats (about 75 %), while Sprague-Dawley and WBN/Kob rats contained only about 50 % of 2B fibers., a2_The percentage of slow type 1 fibers in the EDL was low in all strains (about 5 %). Our results thus show that the individual, age and sex as well as inter-strain differences in muscle fiber type composition should not be ignored when comparing results of different studies. We also demonstrated that the inbred Lewis strain appears to have more “specialized” muscle composition, as its soleus is the “slowest” and its EDL is the “fastest” among the routinely used rat strains., P. Novák, G. Zachařová, T. Soukup., and Obsahuje bibliografii a bibliografické odkazy
In order to re-evaluate the presence and relative quantity of 2b and 2x/d myosin heavy chain (MyHC) transcripts in rat slow soleus muscle by using real time RT-PCR we have compared the available relevant cDNA sequences and designed a new set of primers having similar melting temperatures, matching separate MyHC exons in the regions of maximal differences in MyHC coding sequences, and containing G or C at the 3́-end. These also yielded PCR products of corresponding length, which is an important requirement for real time RT-PCR quantification. The experiments were performed on 8- month-old inbred female Lewis strain rats used in our current study of regenerating transplanted muscles. The real time RT-PCR measurement confirmed the expression of all four MyHC mRNAs (type 1, 2a, 2x/d and 2b) in both fast extensor digitorum longus and slow soleus muscles, although in the soleus muscle of adult rats, only type 1 and 2a protein isoforms can be usually detected, J. Žurmanová, F. Půta, R. Stopková, T. Soukup., and Obsahuje bibliografii a bibliografické odkazy