[Assay of nuclear triiodothyronine receptors in the precentral gyrus in patients with amyotrophic lateral sclerosis].

Abnormality in the receptor of the cell might have some bearing on the selective cellular damage in systemic degenerative diseases. In relation to deranged metabolic turnover of the folate cycle in amyotrophic lateral sclerosis (ALS), we have measured nuclear triiodothyronine receptors (NT3R) in the precentral gyrus, stored at -80 degrees C after autopsy, of 4 ALS patients and 8 patients with non-neurological diseases. Cell nuclei were separated in bulk from about 1 g of grey matter by the method of Løvtrup-Rein & McEwen, and T3-binding assay was carried out by the method of Silva et al. DNA was measured by the method of Giles & Myers based on Burton's method. Specific bindings comprised more than 85% of total bindings. Scatchard analysis showed that the maximal binding capacity, namely the density of NT3R was significantly reduced in ALS, compared to that of the controls. The dissociation constant, namely the affinity was not different between the two groups. The present investigation suggests that NT3R may be reduced in the motoneuron of ALS patients, although the result might merely indicate the loss of nerve cells from the ALS motor cortex. This point should be clarified, but the bulk separation of pure nerve cell nuclei from autopsied human brain has not so far been successful in our laboratory. Action of thyroid hormone in the mature brain has not fully been clarified. Meanwhile, some investigators suggest that the metabolic state of the central nervous system of ALS has a tendency of hypothyroidism. Therefore, the relevance of thyroid hormone to pathogenesis or pathophysiology of ALS will be an important subject in future study.