Compensatory increase in calcium extrusion activity of untreated lymphocytes from swine susceptible to malignant hyperthermia

Peter James O'Brien From the Department of Pathology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.

Search for other papers by Peter James O'Brien in
Current site
Google Scholar
PubMed
Close
 DVM, PhD, DVSc
,
Barbara I. Kalow From the Department of Pathology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.

Search for other papers by Barbara I. Kalow in
Current site
Google Scholar
PubMed
Close
 DVM, MSc
,
Nardia Ali From the Department of Pathology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.

Search for other papers by Nardia Ali in
Current site
Google Scholar
PubMed
Close
 MSc
,
Laurie A. Lassaline From the Department of Pathology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.

Search for other papers by Laurie A. Lassaline in
Current site
Google Scholar
PubMed
Close
, and
John H. Lumsden From the Department of Pathology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.

Search for other papers by John H. Lumsden in
Current site
Google Scholar
PubMed
Close
 DVM, MSc

Click on author name to view affiliation information

SUMMARY

We tested the hypothesis that lymphocytes from swine with susceptibility to malignant hyperthermia (mh) had calcium extrusion activity higher than unaffected swine. Cytoplasmic concentration of ionized calcium was determined by use of dual emission spectrofluorometry and measurement of the ratio of free to calcium-bound form of the fluorescent calcium dye indo-1. Net calcium accumulation and unidirectional calcium extrusion rate were dependent on intracellular calcium concentration. Calcium extrusion from calcium-loaded lymphocytes was monitored while calcium influx was inhibited by suspending the cells in calcium-free medium with a calcium chelator. Net calcium accumulation of untreated lymphocytes was monitored in calcium-replete medium. A novel method of calculation of ionized calcium was used. This method confirmed our previous findings of lower ionized calcium concentration (86 ± 40 and 370 ± 216 nmol/L; P < 0.01) and slower rates of calcium accumulation 39 ± 16 and 127 ± 52 nmol/L/min) in untreated lymphocytes from mh-susceptible swine compared with controls. These changes were attributable to calcium extrusion activity two- to three-fold higher in lymphocytes of mh-susceptible swine (154 ± 36 and 408 ± 47 nmol/L/min at 175 nmol/L; 972 ± 111 and 1,690 ± 505 nmol/L/min at 425 nmol/L). These data were compatible with our model of higher calcium extrusion activity being a compensatory adaptation of mh-susceptible swine lymphocytes to their hypersensitivity to stimuli that increase cytoplasmic calcium concentration.

SUMMARY

We tested the hypothesis that lymphocytes from swine with susceptibility to malignant hyperthermia (mh) had calcium extrusion activity higher than unaffected swine. Cytoplasmic concentration of ionized calcium was determined by use of dual emission spectrofluorometry and measurement of the ratio of free to calcium-bound form of the fluorescent calcium dye indo-1. Net calcium accumulation and unidirectional calcium extrusion rate were dependent on intracellular calcium concentration. Calcium extrusion from calcium-loaded lymphocytes was monitored while calcium influx was inhibited by suspending the cells in calcium-free medium with a calcium chelator. Net calcium accumulation of untreated lymphocytes was monitored in calcium-replete medium. A novel method of calculation of ionized calcium was used. This method confirmed our previous findings of lower ionized calcium concentration (86 ± 40 and 370 ± 216 nmol/L; P < 0.01) and slower rates of calcium accumulation 39 ± 16 and 127 ± 52 nmol/L/min) in untreated lymphocytes from mh-susceptible swine compared with controls. These changes were attributable to calcium extrusion activity two- to three-fold higher in lymphocytes of mh-susceptible swine (154 ± 36 and 408 ± 47 nmol/L/min at 175 nmol/L; 972 ± 111 and 1,690 ± 505 nmol/L/min at 425 nmol/L). These data were compatible with our model of higher calcium extrusion activity being a compensatory adaptation of mh-susceptible swine lymphocytes to their hypersensitivity to stimuli that increase cytoplasmic calcium concentration.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 48 48 10
PDF Downloads 20 20 2
Advertisement