Evidence for the involvement of chromaffin cells in the stimulatory effect of tachykinins on corticosteroid secretion by the frog adrenal gland.

Abstract

The adrenal gland of the frog is innervated by a network of fibers containing two tachykinins (ranakinin and [Leu3,Ile7]neurokinin A), which both stimulate corticosteroid secretion from frog adrenal tissue. The aim of the present study was to determine the mode of action of tachykinins on the frog adrenal gland. Double immunolabeling of tissue sections with a monoclonal antibody to tyrosine hydroxylase and an antiserum to substance P showed that tachykinin-containing fibers are preferentially apposed onto chromaffin cells. Immunocytochemical labeling at the electron microscope level revealed that tachykinin-immunoreactive fibers establish close contacts only with adrenochromaffin cells. Ranakinin stimulated corticosterone and aldosterone secretion from perifused adrenal slices, but had no stimulative effect on dispersed adrenal cells. Cytoautoradiographic labeling of frog adrenal cells in primary culture with [3H]substance P revealed the existence of specific binding sites located exclusively on chromaffin cells. Microfluorimetric measurement of cytosolic calcium concentrations ([Ca2+]i) in cultured adrenal cells showed that ranakinin induced a dose-dependent increase in [Ca2+]i in chromaffin cells (ED50 = 2 x 10(-7) M). In contrast, ranakinin did not affect [Ca2+]i in adrenocortical cells. The present results indicate that in the frog adrenal gland, tachykinin-containing fibers make preferential contacts with chromaffin cells, and tachykinins directly activate chromaffin cells. These data suggest that the stimulative effect of tachykinins on corticosteroid secretion is mediated via presynaptic activation of adrenochromaffin cells.

Activation of EndothelinA Receptors in Frog Adrenocortical Cells Stimulates Both Calcium Mobilization from Intracellular Stores and Calcium Influx through L-Type Calcium Channels

“…Previous studies have shown that, in the frog adrenal gland, regulatory peptides such as ranakinin and pituitary AC-activating polypeptide exert an indirect corticotropic effect via activation of chromaffin cells (27,28). The present study demonstrates that ET-1 induces a direct stimulatory effect on frog adrenocortical cells.…”

In vitro effects of crude extracts of Parkia biglobosa (Mimosaceae), Stereospermum kunthianum (Bignoniaceae) and Biophytum petersianum (Oxalidaceae) on corticosteroid secretion in rat

“…stimulatory action of the peptide on catecholamine secretion [17][18][19]. Similarly, in the frog adrenal gland, tachykinininduced stimulation of corticosteroid production is mediated through activation of chromaffin cells [20]. In the present study, we found that the B. petersianum extract stimulated corticosterone and aldosterone secretion from adrenocortical fragments that were devoid of medullary tissue, indicating that the active compound(s) present in the extract did not act indirectly via stimulation of chromaffin cells.…”

Role of Neuromedins in the Regulation of Adrenocortical Function

“…As evidenced recently (Mazzocchi et al 1995), the aldosterone secretagogue effect of SP probably involves the stimulation of catecholamirie release by adrenal medulla chromaffin cells, and similar mechanisms may be involved in aldosterone secretagogue effects evoked by NKB. Moreover, evidences suggest that similar mechanism of tachykinins action on corticosteroid secretion being present in the frog adrenal gland (Kodjo et al 1995 a). Catecholamines, in turn, are able to modify secretory activity of adrenocortical cells (Bornstein et al 1990(Bornstein et al , 1991.…”