Investigations of the influence of the extra- and intracellular calcium source on secretory processes helps the understanding of the physiology and pathophysiology of secretion. The ratio of the two calcium sources in the activation of secretion depends on the type of secretory cell, on the character of the secretagogue stimulus and the phase of the secretory process. The use of intracellular sources of calcium in the early stage of secretion explains the lack of an inhibitory action of calcium current blockers on the function of some hormonal systems in short-term studies, e.g. the tyrotropic and somatotropic system, or on adrenocortical secretion. Conversely inhibition of some hormonal functions in the curse of prolonged inhibition of calcium currents indicates the importance of the inflow of calcium ions from the extracellular space into the cytosol during long-term regulation of secretion. The author gives an account of the results of investigations which by means of calcium ionophores or calcium current antagonists provide evidence of the importance of an extracellular calcium source in the control of secretion of some systems.

Keywords: Animals; Calcium /physiology/; Calcium Channels /physiology/; Cell Line; Hormones /metabolism/; Humans