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

Abstract

Subclinical form of hypothyroidism was not associated with considerable changes in Ca²⁺ 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 Ca²⁺ 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 Ca²⁺ 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 Ca²⁺ also considerably changed. Hyperthyroidism (2 months) was characterized by a moderate decrease in plasma content of Ca²⁺ 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 Ca²⁺ increased even more markedly, but somewhat decreased in response to addition of 5 mM ATP due to compensation of metabolic acidosis.