Browsing by Subject "Steroid secretion"

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    Paracrine control of steroid hormone secretion by chromaffin cells in the adrenal gland of lower vertebrates
    (F. Hernández y Juan F. Madrid. Universidad de Murcia. Departamento de Biología Celular e Histología, 1998) Mazzocchi, G.; Gottardo, G.; Nussdorfer, G. G.
    The adrenal glands of lowe r vertebrates display a notable intermingling between steroidogenic and chromaffin tissues, which increases from Pisces to Al'es. As in mammals, adrenal chromaffin cells contain and release, in addition to catechol amines, serotonin and several peptides, which may affect the secretory acti vity of steroidogeni c cells in a paracrine manner. Stimulatory molec ul es in c lud e se roto nin , arg inin e-va so tocin. tachykinin s, vasoac ti ve intestinal peptide , pituita ry adenylate cyclase-acti vating peptide and calcitonin generelated peptide: inhibitory molec ul es are dopamine, somatotropic hormone-release inhibiting hormone and ga lanin . Epin ephrine and no repinephrine appe ar to stimulate steroid sec retion in Aves and to inhibit it in Pisces, while their ac tion in Amphibia is controversial. Likewise . atri a l natriureti c peptide exe rts an antisec re ta gog ue ac ti o n in Amphibia and a ma rk ed secretagogue effe ct in Pisces and Aves. The effects of opioids (enkephalins and endorphins) have scarcely been in vesti ga ted a nd th e findin gs obt a ined a re hi g hly qu esti o nabl e. Compared with the ama zin g ma ss of in vestigations carried out in mammals, studies in lower ve rtebrates a re few, and in large part pe rformed in Amphibia and Al'es. It appears that much further work has to be done by comparati ve endocrinologists to fully clari fy the physiolog ica l relevance of th e functi onal interactions between chromaffin and steroidogeni c cells in the adrenal glands of lower vertebrates.
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    The role of neuromedin B in the regulation of rat pituitary-adrenocortical function
    (Murcia : F. Hernández, 1996) Malendowicz, L.K.; Macchi, C.; Nussdorfer, G.G.; Nowak, M.
    The effects of a 7-day administration of neuromedin B (NMB) andlor ( ~ ~D-rphe~12,)-b ornbesin, an NMB-receptor antagonist (NMB-A) on the function of pituitary-adrenocortical axis were investigated in the rat. NMB raised the plasma concentration of aldosterone, without affecting that of ACTH or corticosterone; the simultaneous administration of NMB-A prevented the effect of NMB. Neither NMB nor NMB-A treatments induced significant changes in adenohypophysis and adrenal weights, nor in the average volume of zona glomerulosa and zona reticularis cells. NMB-A administration lowered the volume of zona fasciculata cells, an effect annulled by the concomitant NMB administration. Our results suggest that NMB specifically stimulates aldosterone secretion, and that endogenous NMB or NMB-like peptides exert a tonic stimulating action on the growth of zona fasciculata cells.