title: Ryanodine receptor type 3 does not contribute to contractions in the mouse myometrium regardless of pregnancy.
abstract: Ryanodine receptor type 3 (RyR3) is expressed in myometrial smooth muscle cells (MSMCs). The short isoform of RyR3 is a dominant negative variant (DN-RyR3) and negatively regulates the functions of RyR2 and full-length (FL)-RyR3. DN-RyR3 has been suggested to function as a major RyR3 isoform in non-pregnant (NP) mouse MSMCs, and FL-RyR3 may also be upregulated during pregnancy (P). This increase in the FL-RyR3/DN-RyR3 ratio may contribute to the strong contractions by MSMCs for parturition. In the present study, spontaneous contractions by the myometrium in NP and P mice were highly susceptible to nifedipine but were not affected by ryanodine. Ca2+image analyses under a voltage clamp revealed that the influx of Ca2+through voltage-dependent Ca2+channels did not cause the release of Ca2+from the sarcoplasmic reticulum (SR). Cytosolic Ca2+concentrations ([Ca2+]cyt) in MSMCs were not affected by caffeine. Despite the abundant expression of large conductance Ca2+-activated K+channels in MSMCs, spontaneous transient outward currents were not observed in the resting state because of the substantive lack of Ca2+sparks. Quantitative PCR and Western blot analyses indicated that DN-RyR3 was strongly expressed in the NP myometrium, while the expression of FL-RyR3 and DN-RyR3 was markedly reduced in the P myometrium. The messenger RNA (mRNA) expression of RyR2 and RyR1 was negligible in the NP and P myometria. Moreover, RyR3 knockout mice may become pregnant and deliver normally. Thus, we concluded that none of the RyR subtypes, including RyR3, play a significant role in the regulation of [Ca2+]cytin or contractions by mouse MSMCs regardless of pregnancy.
authors.affiliation: Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, 467-8603, Japan.
authors.forename: Katsuhito
authors.initials: K
authors.lastname: Matsuki
authors.affiliation: Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, 467-8603, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Takemoto
authors.affiliation: Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, 467-8603, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, 467-8603, Japan.
authors.forename: Hisao
authors.initials: H
authors.lastname: Yamamura
authors.affiliation: Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto, 607-8414, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Ohya
authors.affiliation: Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takeshima
authors.affiliation: Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, 467-8603, Japan. yimaizum@phar.nagoya-cu.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Imaizumi
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009119:Muscle Contraction / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D009215:Myometrium / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011247:Pregnancy; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D012333:RNA, Messenger; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002110:Caffeine; D011188:Potassium; D002118:Calcium
keywords: Large conductance Ca2+-activated K+ channels; Myometrium; Ryanodine receptor type 3; Voltage-dependent Ca2+ channel