Multiple calcium channels are required for pituitary adenylate cyclase-activating polypeptide-induced catecholamine secretion from bovine cultured adrenal chromaffin cells

Abstract

The effects of L-, N-, P- and Q-type calcium channel antagonists and (+/-)-BayK-8644 on catecholamine release induced by pituitary adenylate cyclase-activating polypeptide (PACAP-27) were investigated in bovine cultured adrenal chromaffin cells. PACAP-27 induced the release of 4-15% of the total cellular catecholamines over 7 min, with an EC50 of 20 nM and the effect approaching maximum at 100 nM. Catecholamine release was fully dependent on the presence of extracellular calcium. The dihydropyridine nitrendipine which inhibits L-type calcium channels inhibited PACAP-27-induced secretion in a concentration dependent manner with an inhibition of 20-30% at 1 microM. In contrast, (+/-)-BayK-8644, which prolongs the opening of L-type calcium channels produced a concentration-dependent increase in PACAP-27-induced catecholamine release with 1 microM increasing release by 40-60%. Blockade of N-type calcium channels with omega-conotoxin GVIA reduced release by 5-15%. Block of P-type channels with low concentrations of omega-agatoxin IVA (< or = 30 nM) had no significant effect on release, while higher concentrations (100-300 nM) which block Q-type channels reduced release by up to 15%. omega-Conotoxin MVIIC, an antagonist of Q-type calcium channels and also of N- and P-type channels, inhibited release in a concentration-dependent manner with a near maximum effect of 30-50% produced by 300 nM. The combination of omega-conotoxin GVIA and omega-agatoxin IVA reduced release by 40-50%. Addition of omega-conotoxin MVIIC (300 nM) to the combination of omega-conotoxin GVIA (10 nM) and omega-agatoxin IVA (100 nM) did not inhibit catecholamine release more than with omega-conotoxin GVIA and omega-agatoxin IVA alone, indicating that 100 nM omega-agatoxin IVA was sufficient to block the Q-type calcium channels. When nitrendipine was used together with omega-conotoxin GVIA, omega-agatoxin IVA and omega-conotoxin MVIIC, catecholamine release induced by 20 nM or 100 nM PACAP-27 was reduced by 70-85%. Taken together these results suggest that influx of calcium through multiple different voltage-sensitive calcium channels mediate PACAP-27-induced catecholamine release from bovine chromaffin cells, and that L-, N- and Q-channels contribute to this response.

Proadrenomedullin N-Terminal 20 Peptide (PAMP), Acting Through PAMP(12–20)-Sensitive Receptors, Inhibits Ca 2+ -Dependent, Agonist-Stimulated Secretion of Human Adrenal Glands

“…The results of the present study confirm the pivotal role played by Ca 2ϩ channels in the secretory activity of adrenal cells, 23 inasmuch as BAYK-8644, an agonist of the highvoltage-activated L-type Ca 2ϩ channels, 24 evoked a clear-cut secretory response of both human ZG and AM cells. They also clearly demonstrate that PAMP completely reversed the secretory response of both cell types to BAYK-8644 and K ϩ , thereby strongly suggesting that PAMP acts on the human adrenal glands exclusively by inhibiting agonist-elicited Ca 2ϩ influx.…”

Differential Calcium Regulation of Proinflammatory Activities in Human Neutrophils Exposed to the Neuropeptide Pituitary Adenylate Cyclase-Activating Protein

“…In these cells, calcium mobilization has been linked to mechanisms, which are cAMP/PKA and PLC/PKC dependent, cAMP/PKA and PLC independent, and ryanodine/caffeine dependent (4). Calcium influx through L-, N-, and Q-type calcium channels has also been reported (39). In hemopoietic cells, PACAP has been reported to have both pro-and antiinflammatory properties (40).…”

Pituitary Adenylate Cyclase-Activating Polypeptide Induces a Sustained Increase in Intracellular Free Ca2+Concentration and Catecholamine Release by Activating Ca2+Influx via Receptor-Stimulated Ca2+Entry, Independent of Store-Operated Ca2+Channels, and Voltage-Dependent Ca2+Channels in Bovine Adrenal Medullary Chromaffin Cells

“…Tanaka et al (1996) reported that the activation of L-type Ca 2ϩ channels by PACAP is due to a membrane depolarization that depends on PKC-mediated Na ϩ influx in bovine adrenal chromaffin cells. O'Farrell and Marley (1997) analyzed the contributions of various types of VOC to PACAP-induced CA release using the specific blockers of VOC subtypes, and suggested the involvement of L-, N-, and Q-type of VOC. Thus, the contribution of VOC to the PACAP-induced Ca 2ϩ influx was considered a possible mechanism for the Ca 2ϩ influx induced by PACAP in adrenal chromaffin cells.…”

“…For example, several studies have shown that PACAP activates VOC in porcine (Isobe et al, 1993), bovine (Tanaka et al, 1996;O'Farrell and Marley, 1997), and canine (Geng et al, 1997) chromaffin cells. On the other hand, PACAP stimulated cAMP-mediated Ca 2ϩ influx in rat (Przywara et al, 1996) and bovine (Perrin et al, 1995) adrenal chromaffin cells and activated Ca 2ϩ influx through a pathway coupled with phospholipase C (Taupenot et al, 1999) with both adenylate cyclase and phospholipase C in PC12 cells (Osipenko et al, 2000).…”