Ca2+‐dependent cosecretion of adrenomedullin and catecholamines mediated by nicotinic receptors in bovine cultured adrenal medullary cells

Abstract

Bovine cultured adrenal medullary cells (4 × 10⁶) contained 4266.5 ± 370.0 fmol of immunoreactive adrenomedullin and 373.4 ± 32.6 mnol of catecholamines. Nicotinic (but not muscarinic) receptors mediated the Ca²⁺-dependent co-secretion of adrenomedullin and catecholamines, with the molar ratio of adrenomedullin/catecholamines secreted into the medium being equal to the ratio stored in the cells. The concentration-response curve of carbachol for adrenomedullin secretion (EC₅₀ 42 μM) was similar to that for catecholamine secretion (EC₅₀ 63 μM). Reverse phase HPLC analysis showed that immunoreactive adrenomedullins in the cells and secreted into the medium were both eluted exclusively at the position almost identical to synthetic human adrenomedullin[1–52]NH₂.