Expression of sarcoplasmic-endoplasmic reticulum Ca-ATPase isoforms in masticatory muscles.
The aim of this study was to characterize the sarcoplasmic-endoplasmic reticulum Ca-ATPase (SERCA) isoforms in rabbit masticatory muscles compared with those in fast-twitch muscle. It was hypothesized that combined expression of the SERCA isoforms in fast- and slow-twitch muscles accounts for lower Ca-ATPase activity. SERCA was isolated by differential centrifugation, the isoforms were determined by ELISA, and the activity of each isoform was measured using a colorimetric method. Activity was tested for significance by anova, and the distribution of isoforms was assessed using the chi-square test (P < 0.05) and correlated to SERCA activity using Spearman's rank correlation. SERCA1 was predominant (90.5%) in fast-twitch muscle, whereas a mixture of SERCA isoforms was found in masticatory muscles: 62-78% was SERCA2, 20-37% was SERCA1, and the SERCA3 content was negligible. Depressor muscles showed a significantly higher content (77.8%) of SERCA2, and elevator muscles showed a higher content (35.4%) of SERCA1. Elevator muscles showed higher expression of SERCA2a (58%), and depressor muscles showed higher expression of SERCA2b (20%). The SERCA1 content was mainly SERCA1a and significantly higher for elevator muscles (33%), whereas depressor muscles showed a higher content of SERCA1b (4%). The SERCA1 content of fast-twitch muscle was mainly SERCA1a (88.5%). It is concluded that the mixture of different SERCA isoforms, along with a substantial content of SERCA2b, in masticatory muscles would support lower Ca-ATPase activity and calcium transport.
Biophysics Department, School of Dentistry, University of Buenos Aires, Buenos Aires, Argentina.
Gabriel A
GA
Sánchez
Pablo W
PW
Trinks
Susana B
SB
Richard
Daniel E
DE
Di Croce
Delia
D
Takara
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D007527:Isoenzymes / Q000032:analysis / Q000145:classification; D008297:Male; D008406:Masseter Muscle / Q000201:enzymology; D008410:Masticatory Muscles / Q000201:enzymology*; D018656:Muscle Fibers, Fast-Twitch / Q000201:enzymology; D018657:Muscle Fibers, Slow-Twitch / Q000201:enzymology; D009334:Neck Muscles / Q000201:enzymology; D011626:Pterygoid Muscles / Q000201:enzymology; D011817:Rabbits; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000032:analysis* / Q000145:classification; D013703:Temporal Muscle / Q000201:enzymology
D007527:Isoenzymes; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases
Ca-ATPase; masticatory muscles; sarcoplasmic reticulum; sarcoplasmic-endoplasmic reticulum Ca2+-dependent adenosine triphosphatase