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Effects of the halothane-sensitivity gene on sarcoplasmic reticulum function
J R Mickelson1, E M Gallant, W E Rempel
1Department of Veterinary Biology, University of Minnesota, St. Paul 55108.
The American Journal of Physiology
|October 1, 1989
Summary
Pigs with the halothane-sensitivity gene show altered muscle responses. Their sarcoplasmic reticulum releases calcium faster and binds ryanodine with higher affinity, indicating a distinct heterozygote phenotype.
Area of Science:
- Physiology
- Molecular Biology
- Genetics
Background:
- Pigs heterozygous for the halothane-sensitivity gene display unique in vivo and in vitro muscle responses to halothane.
- Understanding the genetic basis of halothane sensitivity is crucial for animal health and research models.
Purpose of the Study:
- To investigate the functional characteristics of heavy sarcoplasmic reticulum (SR) in pigs with different halothane-sensitivity gene genotypes.
- To determine if heterozygous pigs exhibit a distinct phenotype regarding SR calcium release and ryanodine binding.
Main Methods:
- Isolation of heavy sarcoplasmic reticulum (SR) preparations from pig muscles across three genotypes (homozygous normal, heterozygous, homozygous sensitive).
- Measurement of calcium release rates from SR.
- Assessment of [3H]ryanodine binding affinity to SR to evaluate the ryanodine receptor.
Main Results:
- SR from homozygous halothane-sensitive pigs exhibited approximately twice the calcium release rate compared to homozygous normal pigs.
- In homozygous halothane-sensitive pigs, [3H]ryanodine binding to SR showed higher affinity (Kd = 70-90 nM) than in homozygous normal pigs (Kd = 265 nM).
- Heterozygous pigs displayed intermediate values for both calcium release rate and [3H]ryanodine binding affinity (Kd = 192 nM).
Conclusions:
- The study confirms a distinct heterozygote phenotype in pigs carrying one copy of the halothane-sensitivity gene, evidenced by altered SR calcium release and ryanodine binding.
- These findings suggest that the protein product of the halothane-sensitivity gene is closely linked to, or identical with, the sarcoplasmic reticulum calcium release channel-ryanodine receptor protein.