Simultaneous monitoring of cytosolic free calcium and exocytosis at the single cell level.

Abstract Quinacrine, a fluorescent basic molecule, accumulates in secretory granules of pituitary cells, as was revealed by its colocalization with immunoreactive prolactin. Thus quinacrine fluorescence may be used to monitor secretory activity at the single cell level. Rat pituitary cells in primary culture were loaded with quinacrine and stimulated with physiological secretagogues, such as thyrotrophin-releasing hormone or bradykinin, which induced a multiphasic lowering of fluorescence, corresponding to the loss of quinacrine contained in exocytosed granules.

Peptides of the neurointermediary lobe of rat pituitary stimulate GH secretion in vitro.

alpha-MSH and other fragments of ACTH are potent stimulators of GH release in vivo. The action of such peptides and of extracts of the neurointermediary lobe (NIL) of rat pituitary, a source of endogenous MSH-related peptides, on GH release was investigated in vitro. Peptides with the core sequence of alpha-MSH stimulate GH secretion by primary cultures of rat anterior pituitary cells; however, both the absolute and the relative potencies of these peptides exclude the involvement of melanotropic receptors comparable in specificity to the extrapituitary receptors for these hormones.