牛腎上腺髓質中調控兒茶酚胺分泌之成分鑑定

Abstract

腎上腺髓質嗜鉻細胞能受乙醯膽鹼刺激而分泌兒茶酚胺。在分泌兒茶酚胺的同時，嗜鉻細胞也釋出如水溶性蛋白質、神經勝?及核?酸等分子。這些隨同兒茶酚胺釋出的分子具有回饋調控兒茶酚胺分泌的功能。本研究從牛腎上腺髓質粗抽取物，經由逆相高壓液相層析法的純化，獲得一能增加基礎分泌而抑制菸鹼刺激之分泌成分。此成分分子量小於 3000 Dalton，且經加熱處理或胰蛋白?作用後仍具有生物活性。但在pronase E處理後，其活性卻遭破壞。因此，此調控兒茶酚胺分泌之物質可能為勝?。於其作用機制的探討上，此調控物質能抑制因刺激菸鹼受器及高鉀溶液所引發的細胞內鈣離子濃度上升及45Ca2＋之攝取，而此物質本身卻可促進鈣離子濃度上升，但是對通透化細胞分泌腎上腺素沒有影響，根據以上的結果顯示此物質可能作用在鈣離子通道上。

Adrenal medulla chromaffin cells are stimulated by acetylcholine to secrete catecholamines. Together with catecholamines, other molecules such as soluble proteins, neuropeptides and neucleotides are also secreted from chromaffin cells. These molecules may modulate the secretory activity after being released. In this study, we have partially purified a component(s) from bovine adrenal medulla by reversed-phase high pressure liquid chromatography. This component possesed the activity to enhance basal secretion but inhibited DMPP-induced secretion from chromaffin cells. The activity was not lost after heat or trypsin treatment, but was destroyed by pronase E treatment. Our results suggest that the active substance is a peptide with a molecular weight smaller than 3000 Da. This component by itself increased the intracellular calcium concentration ([Ca2+]i) but inhibited DMPP- or high K+- induced [Ca2+]i rise. Futhermore, this active substance blocked DMPP- and high K+- induced 45Ca2+ uptake, and had no effect on Ca2+-dependent catecholamine secretion from digitonin-permeabilized chromaffin cells. It is likely that the active substance purified from bovine adrenal medulla affects secretion at step(s) before [Ca2+]i rise, possibly at calcium channels.