Neurohormonal regulation of calcium in the cell

Neurohormone C (NC) is a glycopeptide isolated from bovine hypothalamus, which inhibits Ca-calmodulin (CaM)-dependent cAMP and cGMP phosphodiesterase (PDE) and is a regulator of Ca in the cell. Distribution of [⁴⁵Ca]CaCl₂ in the mitochondria and reticulum (SR) of heart and brain mitochondria and changes of Ca-binding proteins in these organelles under NC influence have been studied in the myocardium before and after isoproterenol-induced necrosis. Intraperitoneal administration of 80–100 mU of PDE inhibitory activity of NC to rats did not cause any noticeable changes in the protein content of intracellular organelles, but altered the affinity of certain proteins to⁴⁵Ca²⁺. This property of NC was especially noticable after isoproterenol necrosis. Necrotic injury of the myocardium induced Ca²⁺ storage in the mitochondria and SR of brain, and decreased the Ca²⁺ concentration in myocardial mitochondria. NC injection to the animals with necrosis was followed by Ca²⁺ release from all the studied organelles.