Mickelson J R, Ervasti J M, Litterer L A, Campbell K P, Louis C F
Department of Veterinary PathoBiology, University of Minnesota, St. Paul 55108.
Am J Physiol. 1994 Jul;267(1 Pt 1):C282-92. doi: 10.1152/ajpcell.1994.267.1.C282.
The content of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase, transverse tubule dihydropyridine receptor (DHPR), and SR ryanodine receptor (RyR) was determined in muscle of pigs homozygous for the normal RyR allele and homozygous or heterozygous for the malignant hyperthermia-susceptible (MHS) RyR allele. Total muscle membranes isolated from 1-day-old pigs of the three different genotypes did not differ in the content of any of these proteins. However, at 28 days of age, crude membranes and total muscle homogenates from homozygous MHS pigs exhibited only 61-81% of the [3H]PN 200-110 or [3H]ryanodine binding of identical preparations isolated from normal pigs; these MHS membranes also contained only 50% of the normal content of each of the DHPR subunits. The crude membranes and muscle homogenates from heterozygous pigs were intermediate to both types of homozygotes in terms of [3H]PN 200-110 binding, [3H]ryanodine binding, and the content of the DHPR subunits. However, membrane preparations enriched in triadic junctional proteins isolated from 3- to 4-mo-old pigs of the three different genotypes did not differ in their [3H]PN 200-110 binding, [3H]ryanodine binding, or Ca(2+)-ATPase activities. We conclude that, although the stoichiometry of the RyR to DHPR is not altered, the presence of the MHS RyR allele during muscle development results in a decreased relative content of these two proteins. This is probably due to a lower junctional membrane content and may be an important ultrastructural consequence of the altered sarcoplasmic Ca2+ regulation in MHS muscle.
在正常兰尼碱受体（RyR）等位基因纯合以及恶性高热易感（MHS）RyR等位基因纯合或杂合的猪肌肉中，测定了肌浆网（SR）Ca(2+) - ATP酶、横小管二氢吡啶受体（DHPR）和SR兰尼碱受体（RyR）的含量。从三种不同基因型的1日龄仔猪分离得到的总肌膜，这些蛋白质的含量没有差异。然而，在28日龄时，纯合MHS猪的粗膜和总肌肉匀浆中，[3H]PN 200 - 110或[3H]兰尼碱结合量仅为从正常猪分离得到的相同制剂的61 - 81%；这些MHS膜中每个DHPR亚基的正常含量也仅为50%。杂合猪的粗膜和肌肉匀浆在[3H]PN 200 - 110结合、[3H]兰尼碱结合以及DHPR亚基含量方面介于两种纯合子之间。然而，从三种不同基因型的3至4月龄猪分离得到的富含三联体连接蛋白的膜制剂，其[3H]PN 200 - 110结合、[3H]兰尼碱结合或Ca(2+) - ATP酶活性没有差异。我们得出结论，尽管RyR与DHPR的化学计量没有改变，但在肌肉发育过程中MHS RyR等位基因的存在导致这两种蛋白质的相对含量降低。这可能是由于连接膜含量较低，并且可能是MHS肌肉中肌浆Ca2+调节改变的一个重要超微结构后果。
