Pituitary adenylate cyclase-activating polypeptide, vasoactive intestinal polypeptide and their receptors: distribution and involvement in the secretion of Podarcis sicula adrenal gland

Abstract

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are regulatory neuropeptides of the hypothalamus-hypophyseal-adrenal axis, acting via the common receptors VPAC 1 and VPAC 2 and the selective PACAP receptor PAC 1 . In the adrenal glands of the Italian wall lizard, Podarcis sicula, the presence of VIP in chromaffin cells, and the VIP-stimulated release of catecholamine and aldosterone in vivo, was previously shown. To examine the localization of both peptides and receptors and their mRNAs in the adrenal gland of P. sicula, immunohistochemistry and in situ hybridization were performed: PACAP and its mRNA were detected in chromaffin cells, VPAC 1 was found associated with steroidogenic tissue, VPAC 2 and PAC 1 with chromaffin tissue. Using 'far western blot' technique, we showed the presence of specific binding sites for VIP/PACAP in the adrenal glands of the lizard. The effects of both VIP and PACAP on the adrenal cells of the lizard were examined in vitro in adrenal cell co-cultures: both VIP and PACAP enhanced catecholamine, corticosterone and aldosterone release from adrenal cell co-culture in a time-and dose-dependent manner. The catecholamine release was inhibited by PAC 1 antagonist and in VPAC 2 immunoneutralized adrenal cells. The effects of VIP and PACAP on aldosterone secretion were counteracted by VPAC 1 antagonist administration in vitro. Corticosterone secretion elicited by VIP was not blocked by VPAC 1 antagonist, while the PACAP-induced release of corticosterone was blocked by the antagonist. Overall, our investigations indicate that these neuropeptides of the secretin superfamily can act not only as neurotransmitters but also as autocrine and paracrine regulators on chromaffin and cortical cells, being important mediators of the non-cholinergic system in the lizard adrenal gland.

Pituitary Adenylate Cyclase-Activating Polypeptide and Its Receptors: 20 Years after the Discovery

“…In mammals, PACAP is found in the adrenal medulla (Shiotani et al, 1995), where it is contained both in chromaffin cells (Holgert et al, 1996) and in fibers (Frödin et al, 1995;Moller and Sundler, 1996;Tornøe et al, 2000). In the Italian wall lizard, Podarcis sicula, PACAP and its mRNA are detected in chromaffin cells, whereas in the frog adrenal gland, PACAP-LI is restricted to nerve fibers that contact either chromaffin cells or steroid-producing cells (Yon et al, 1993a;Valiante et al, 2008). It has been suggested that in the rat and dog adrenal gland, PACAP released from nerve endings contributes to neurally evoked catecholamine release (Fukushima et al, 2001a;Lamouche and Yamaguchi, 2003).…”

“…In adrenal chromaffin cells, PACAP exerts a stimulatory action on catecholamine secretion Isobe et al, 1993;Chowdhury et al, 1994;Guo and Wakade, 1994;Houchi et al, 1994;Perrin et al, 1995;Neri et al, 1996;Jorgensen et al, 2000;Fukushima et al, 2002;Douglas et al, 2008;Valiante et al, 2008). PACAP also stimulates the release of brain natriuretic peptide and enkephalins, two regulatory peptides that are cosequestered with catecholamines in chromaffin granules (Babinski et al, 1996;Hahm et al, 1998) as well as a 15-fold increase in VIP mRNA expression (Lee et al, 1999a).…”

Circulating non-immune IgG complexes in health and disease

“…The microassay based on the adsorption of total serum IgG on the Protein G-Sepharose beads was used for the isolation of the non-immune complexes and the adsorbed proteins were eluted from the beads directly on the nitrocellulose membrane [18][19][20][21]. The identification of the IgG-associated CD4 was performed by anti-CD4 monoclonals.…”

Sex steroid hormone secretion in the wall lizard Podarcis sicula testis: The involvement of VIP

“…The experiments were approved by institutional committees (Ministry of Health, Italy) and organized to minimize the number of animals used. The animals were sacrificed by decapitation after deep anesthesia with ketamine hydrochloride (Parke‐Davis, Berlin, Germany) 325 pg/g of body weight (Valiante et al, , ). Sexual maturity of each animal was determined by morphological parameters and by histological analysis (Agnese et al, ,b; Rosati et al, ).…”