Changes in intra- and extracellular Ca2+ concentration and prostaglandin E2 synthesis in osteoblasts of the femoral bone in experimental hyper- and hypothyroidism.

Subclinical form of hypothyroidism was not associated with considerable changes in Ca(2+) content in osteoblasts and blood plasma and in the content of ATP and prostaglandin E2. Activation of prostaglandin E2 synthesis in response to binding of extracellular Ca(2+) in osteoblasts in the absence of ATP was less pronounced (by 11%) compared to the control. Progression of hypothyroidism and development of clinical signs of the disease were accompanied by a decrease in Ca(2+) content in osteoblasts and plasma by 45 and 12%, respectively, and ATP content in osteoblasts by 30%, and by activation of prostaglandin E2 synthesis by 117%. Moreover, the synthesis of prostaglandins in response to binding of extra- and intracellular Ca(2+) also considerably changed. Hyperthyroidism (2 months) was characterized by a moderate decrease in plasma content of Ca(2+) by 15% and ATP by 25%, together with an increase in prostaglandin E2 level by 55.5%. The release of prostaglandin E2 in response to chelation of extracellular Ca(2+) increased even more markedly, but somewhat decreased in response to addition of 5 mM ATP due to compensation of metabolic acidosis.