[Participation of synaptotagmin in release of catecholamines in rat adrenal chromaffin cells].

Exocytosis is known to provide such a vital processes as the release of neurotransmitters in synaptic transmission or release of hormones during secretion. The main mechanism of exocytotic process occurs through the specialized protein complex called the SNARE-complex. Due to its activity the fusion of vesicular and plasma membrane occurs and fusion pore is formed through which a content of vesicles is released outside. It is believed that just synaptotagmins which are Ca2+ dependent proteins, responsible for initiation of the process of Ca(2+)-dependent exocytosis. Synaptotagmins are located at the membrane of the vesicles and can bind two or three Ca2+ ions. In our research, we studied the role of one of the most common isoform of synaptotagmines--synaptotagmin-1. For this we used an injection of antibodies arised to synaptotagmin-1 (anti-STg-1) into isolated rat adrenal chromaffin cells to depress the function of this protein. Catecholamine secretion was measured by amperometric method. Our results showed that an exclusion of synaptotagmin-1 function in tested cells resulted in significant suppression of secretion. These data allow us to conclude that synaptotagmin-1 is a key protein which is needed for Ca(2+)-dependent exocytosis in chromaffin cells.

[Ultrastructural characteristics of rat adrenal cortex cultured cells in the norm and after calcium ionophore A23187 and adrenocorticotropic hormone application]. / Osoblyvosti ul'trastruktury kul'tural'nykh klityn kory nadnyrkovykh zaloz shchura u normi ta pislia aplikatsiï kal'tsiievoho ionoforu A23187 ta adrenokortykotropnoho hormonu.

The ultrastructure of a fasciculata-reticularis zone cells of a rat adrenal cortex in norm, and after application of adrenocorticotropic hormone (ACTH) and calcium ionophore A23187 was investigated. In the control it has been revealed three types of cells which differed on the ultrastructure. ACTH or ionophore A23187 application resulted in disappearance of a difference in ultrastructure of cells of different types, also all cells got morphological attributes of accelerated steroidogenesis. The probable role of cells with different types of ultrastructure for fasciculata-reticularis zone function, and also prospective participation of calcium ions in ACTH influences on ultrastructure of a fasciculata-reticularis zone is discussed.

[Ultrastructural characteristics of lipid droplets in rat adrenocortical cells from zona fasciculata-reticularis]. / Osoblyvosti ul'trastruktury lipidnykh krapel' u klitynakh puchkovo-sitchastoï zony kory nadnyrkovykh zaloz shchura in vitro.

One day cultured adrenocortical cells from zona fasciculata-reticularis were used in morphological experiments. The electron-microscopic and imaging analysis methods were used for the investigation of intracellular ultrastructure of these cells. Experiments which conducted in control conditions, allowed us to allocate three types of cells which differed by ultrastructure of the mitochondria, lipid droplets, smooth endoplasmic reticulum and dense bodies. It was shown that lipid droplets with light and homogeneous matrix, met more often in cells with morphological attributes of high intensity of steroidogenesis. On the contrary, lipid droplets, with dark matrix and a dense edging, met more often in cells which having morphological attributes-of low intensity of steroidogenesis. Ionophore A23187 or adrenocorticotropic hormone application resulted in reduction of lipid droplets diameter and in simultaneous increase in density of their arrangement in cytoplasm. At the same time droplet matrix became light and homogeneous in all cells. Thus, the ultrastructure of lipid droplet matrix is sensitive to change of calcium ions concentration in cytoplasm. Processes which result in change of lipid droplet ultrastructure, probably, are connected to steroidogenesis, nevertheless, this question requires further investigation. The lipid droplets" ability to form morphological contacts with smooth endoplasmic reticulum, mitochondria, nuclear and cellular membranes is also discussed.