Helman J, Kuyatt B L, Takuma T, Seligmann B, Baum B J
J Biol Chem. 1986 Jul 5;261(19):8919-23.
ATP-dependent Ca2+ transport was studied in basolateral membrane vesicles prepared from rat parotid gland slices incubated without or with agents which increase cyclic AMP. Isoproterenol (10(-5) M), forskolin (2 X 10(-6) M) and 8-bromocyclic AMP (2 X 10(-3) M) all increased ATP-dependent 45Ca2+ uptake 1.5- to 3-fold. The effect of isoproterenol was concentration-dependent and blocked by the beta-adrenergic antagonist propranolol. Enhanced uptake did not appear an artifact of vesicle preparation as apparent vesicle sidedness, 45Ca2+ efflux rates, specific activity of marker enzymes and equilibrium Ca2+ content were identical in vesicle preparations from control and 8-bromocyclic AMP-treated slices. Kinetic studies showed the ATP-dependent Ca2+ transport system in vesicles from 8-bromocyclic AMP-treated slices displayed a approximately 50% increase in Vmax and in Km Ca2+, compared to controls. The data suggest that physiological secretory stimuli to rat parotid acinar cells, which involve cyclic AMP, result in a readjustment of the basolateral membrane ATP-dependent Ca2+ pump.
在从大鼠腮腺切片制备的基底外侧膜囊泡中研究了ATP依赖的Ca2+转运，这些切片在无或有增加环磷酸腺苷（cAMP）的试剂存在下孵育。异丙肾上腺素（10(-5) M）、毛喉素（2×10(-6) M）和8-溴环磷酸腺苷（2×10(-3) M）均使ATP依赖的45Ca2+摄取增加了1.5至3倍。异丙肾上腺素的作用呈浓度依赖性，并被β-肾上腺素能拮抗剂普萘洛尔阻断。摄取增强并非囊泡制备的假象，因为在对照和8-溴环磷酸腺苷处理切片的囊泡制备中，明显的囊泡方向性、45Ca2+流出率、标记酶的比活性和平衡Ca2+含量均相同。动力学研究表明，与对照相比，来自8-溴环磷酸腺苷处理切片的囊泡中ATP依赖的Ca2+转运系统的Vmax和Km Ca2+增加了约50%。数据表明，对大鼠腮腺腺泡细胞的生理性分泌刺激涉及环磷酸腺苷，导致基底外侧膜ATP依赖的Ca2+泵重新调整。
