PARATHYROID ABLATION IN DYSTROPHIC HAMSTERS - EFFECTS ON CA CONTENT AND HISTOLOGY OF HEART, DIAPHRAGM, AND RECTUS FEMORIS

Cumulative evidence indicates that there is an increased accumulation of Ca in dystrophic muscle and that this may have a pathophysiological role in the progression of the dystrophic process. The accumulation may be related to a defect of the plasma membrane. Because parathyroid hormone (PTH) stimulates Ca influx into the cytosol, the chronic effects of surgical ablation of the parathyroid glands on muscle Ca, Mg, protein synthesis, histology and plasma creatine phosphokinase (CPK), Ca and Mg were studied in normal and dystrophic (BIO 14.6) hamsters. Thyroparathyroidectomized (TPTX) hamsters receiving replacement doses of L-thyroxine were killed at age 90 days, 55 days after TPTX. In dystrophic hamsters TPTX causes a marked reduction in muscle Ca accumulation, levels of plasma CPK and intensity of histological changes in the heart. These changes were independent of the levels of plasma Ca and were not observed in normal hamsters. PTH accentuates the dystrophic process, probably by enhancing the already increased Ca flux into muscle (apparently caused by defective sarcolemma). Normal secretion of PTH may have a deleterious effect in congenital or acquired conditions associated with altered plasma membranes.