PMID- 8046643
OWN - NLM
STAT- MEDLINE
DCOM- 19940901
LR  - 20191210
IS  - 0022-3751 (Print)
IS  - 1469-7793 (Electronic)
IS  - 0022-3751 (Linking)
VI  - 476
IP  - 2
DP  - 1994 Apr 15
TI  - Relaxation in rabbit and rat cardiac cells: species-dependent differences in 
      cellular mechanisms.
PG  - 279-93
AB  - The roles of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase and Na(+)-Ca2+ 
      exchange in Ca2+ removal from cytosol were compared in isolated rabbit and rat 
      ventricular myocytes during caffeine contractures and electrically stimulated 
      twitches. Cell shortening and intracellular calcium concentration ([Ca2+]i) were 
      measured in indo-1-loaded cells. Na(+)-Ca2+ exchange was inhibited by replacement 
      of external Na+ by Li+. To avoid net changes in cell or SR Ca2+ load during a 
      twitch in 0 Na+ solution, intracellular Na+ (Na+i) was depleted using a long 
      pre-perfusion with 0 Na+, 0 Ca2+ solution. SR Ca2+ accumulation was inhibited by 
      caffeine or thapsigargin (TG). Relaxation of steady-state twitches was 2-fold 
      faster in rat than in rabbit (before and after Na+i depletion). In contrast, 
      caffeine contractures (where SR Ca2+ accumulation is inhibited), relaxed faster 
      in rabbit cells. Removal of external Na+ increased the half-time for relaxation 
      of caffeine contractures 15- and 5-fold in rabbit and rat myocytes respectively 
      (and increased contracture amplitude in rabbit cells only). The time course of 
      relaxation in 0 Na+, 0 Ca2+ solution was similar in the two species. Inhibition 
      of the Na(+)-Ca2+ exchange during a twitch increased the [Ca2+]i transient 
      amplitude (delta[Ca2+]i) by 50% and the time constant of [Ca2+]i decline (tau) by 
      45% in rabbit myocytes. A smaller increase in tau (20%) and no change in 
      delta[Ca2+]i were observed in rat cells in 0 Na+ solution. [Ca2+]i transients 
      remained more rapid in rat cells. Inhibition of the SR Ca(2+)-ATPase during a 
      twitch enhanced delta[Ca2+]i by 25% in both species. The increase in tau after TG 
      exposure was greater in rat (9-fold) than in rabbit myocytes (2-fold), which 
      caused [Ca2+]i decline to be 70% slower in rat compared with rabbit cells. The 
      time course of [Ca2+]i decline during twitch in TG-treated cells was similar to 
      that during caffeine application in control cells. Combined inhibition of these 
      Ca2+ transport systems markedly slowed the time course of [Ca2+]i decline, so 
      that tau was virtually the same in both species and comparable to that during 
      caffeine application in 0 Na+, 0 Ca2+ solution. Thus, the combined participation 
      of slow Ca2+ transport mechanisms (mitochondrial Ca2+ uptake and sarcolemmal 
      Ca(2+)-ATPase) is similar in these species. We conclude that during the decline 
      of the [Ca2+]i transient, the Na(+)-Ca2+ exchange is about 2- to 3-fold faster in 
      rabbit than in rat, whereas the SR Ca(2+)-ATPase is 2- to 3-fold faster in the 
      rat.(ABSTRACT TRUNCATED AT 400 WORDS)
FAU - Bassani, J W
AU  - Bassani JW
AD  - Department of Physiology, Loyola University School of Medicine, Maywood, IL 
      60153.
FAU - Bassani, R A
AU  - Bassani RA
FAU - Bers, D M
AU  - Bers DM
LA  - eng
GR  - HL-30077/HL/NHLBI NIH HHS/United States
PT  - Comparative Study
PT  - Journal Article
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - England
TA  - J Physiol
JT  - The Journal of physiology
JID - 0266262
RN  - 0 (Carrier Proteins)
RN  - 0 (Sodium-Calcium Exchanger)
RN  - 3G6A5W338E (Caffeine)
RN  - 9NEZ333N27 (Sodium)
RN  - EC 7.2.2.10 (Calcium-Transporting ATPases)
RN  - SY7Q814VUP (Calcium)
SB  - IM
MH  - Action Potentials/physiology
MH  - Animals
MH  - Caffeine/pharmacology
MH  - Calcium/metabolism
MH  - Calcium-Transporting ATPases/metabolism
MH  - Carrier Proteins/physiology
MH  - Electric Stimulation
MH  - Fluorescence
MH  - Heart/drug effects/*physiology
MH  - In Vitro Techniques
MH  - Male
MH  - Myocardial Contraction/drug effects/*physiology
MH  - Myocardium/*cytology/enzymology
MH  - Rabbits
MH  - Rats
MH  - Rats, Sprague-Dawley
MH  - Sarcoplasmic Reticulum/enzymology
MH  - Sodium/metabolism
MH  - Sodium-Calcium Exchanger
MH  - Species Specificity
PMC - PMC1160440
EDAT- 1994/04/15 00:00
MHDA- 1994/04/15 00:01
PMCR- 1994/04/15
CRDT- 1994/04/15 00:00
PHST- 1994/04/15 00:00 [pubmed]
PHST- 1994/04/15 00:01 [medline]
PHST- 1994/04/15 00:00 [entrez]
PHST- 1994/04/15 00:00 [pmc-release]
AID - 10.1113/jphysiol.1994.sp020130 [doi]
PST - ppublish
SO  - J Physiol. 1994 Apr 15;476(2):279-93. doi: 10.1113/jphysiol.1994.sp020130.