Age-related changes in sarcoplasmic reticulum Ca(2+)-ATPase and alpha-smooth muscle actin gene expression in aortas of normotensive and spontaneously hypertensive rats.
The expression of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase gene and the SR Ca2+ pump function were investigated in thoracic aortas of 5- and 17-week-old normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). The relative level of the two isoforms of SR Ca(2+)-ATPase mRNA expressed in the aorta (i.e., SERCA 2a and SERCA 2b) was determined by quantitative S1 nuclease protection analysis and normalized to the level of alpha-smooth muscle (alpha-Sm) actin mRNA. The level of alpha-Sm actin mRNA itself was normalized to the level of 18S ribosomal RNA using slot-blot hybridization assays. Total SR Ca2+ pump activity was estimated by measuring the rate of oxalate-supported Ca2+ uptake in homogenates. At 5 weeks, the amount of SERCA 2a and SERCA 2b mRNA, normalized to 18S ribosomal RNA, and the ratio of alpha-Sm actin mRNA to 18S RNA were identical in SHR and WKY rats. The Ca2+ pump activity was similar in the two strains of rats at 5 weeks. From 5 to 17 weeks, the amount of SERCA 2a mRNA increased in both strains while the level of SERCA 2b mRNA remained constant. The Ca2+ pump activity was unchanged in SHRs and tended to decrease in WKY rats. Accordingly, the change in the ratio of the SR Ca(2+)-ATPase mRNA isoforms does not appear to influence SR function. The level of alpha-Sm actin mRNA and SERCA 2a mRNA increased in parallel from 5 to 17 weeks in both strains.(ABSTRACT TRUNCATED AT 250 WORDS)
Le Jemtel
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INSERM U275-LOA, ENSTA-Ecole Polytechnique, Palaiseau, France.
Lambert
F
F
Levitsky
D O
DO
Clergue
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M
Anger
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M
Gabbiani
G
G
Lompré
A M
AM
D000199:Actins / Q000235:genetics* / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D001013:Aorta, Thoracic / Q000201:enzymology / Q000378:metabolism*; D015152:Blotting, Northern; D000252:Calcium-Transporting ATPases / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D006973:Hypertension / Q000235:genetics* / Q000378:metabolism; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*
D000199:Actins; D012333:RNA, Messenger; D000252:Calcium-Transporting ATPases