title: Failure of short term stimulation to reduce sarcoplasmic reticulum Ca(2+)-ATPase function in homogenates of rat gastrocnemius.
abstract: To examine the effect of short term intense activity on sarcoplasmic reticulum (SR) Ca2+ sequestering function, the gastrocnemius (G) muscles of 11 anaesthetized male rats (weight, 411 +/- 8 g, X +/- SE) were activated using supramaximal, intermittent stimulation (one train of 0.2 msec impulses per sec of 100 msec at 100 Hz). Homogenates were obtained from stimulated white (WG-S) and red (RG-S) tissues, assayed for Ca2+ uptake and maximal Ca2+ ATPase activity and compared to contralateral controls (WG-C, RG-C). Calcium uptake (nmoles/mg protein/min) determined using Indo-1 and at [Ca2+]i concentrations between 300-400 nM was unaffected (p > 0.05) by activity in both WG (6.14 + 0.43 vs 5.37 + 0.43) and RG (3.21 + 0.18 vs 3.07 + 0.20). Similarly, no effect (p > 0.05) of contractile activity was found for maximal Ca2+ ATPase activity (mumole/mg protein/min) determined spectrophotometrically in RG (0.276 + 0.03 vs 0.278 + 0.02). In WG, Ca2+ ATPase activity was 15% higher in WG-S compared to WG-C (0.412 + 0.03 vs 0.385 + 0.04). Repetitive stimulation resulted in a reduction in tetanic tension of 74% (p < 0.05) by 2 min in the G muscle. By the end of the stimulation period, ATP concentration was reduced (p < 0.05) by 57% in the WG and by 47% in the RG.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Kinesiology, University of Waterloo, Ontario, Conada.
authors.forename: J
authors.initials: J
authors.lastname: Dossett-Mercer
authors.forename: H
authors.initials: H
authors.lastname: Green
authors.forename: E R
authors.initials: ER
authors.lastname: Chin
authors.forename: F
authors.initials: F
authors.lastname: Grange
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D003401:Creatine / Q000378:metabolism; D004558:Electric Stimulation; D006003:Glycogen / Q000378:metabolism; D007291:Inosine Monophosphate / Q000378:metabolism; D007773:Lactates / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000201:enzymology* / Q000378:metabolism
chemical_list: D007773:Lactates; D010710:Phosphates; D011773:Pyruvates; D010725:Phosphocreatine; D007291:Inosine Monophosphate; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006003:Glycogen; D000252:Calcium-Transporting ATPases; D003401:Creatine; D002118:Calcium