Abramowitz J, Campbell A R
Biochem Biophys Res Commun. 1983 Oct 31;116(2):574-80. doi: 10.1016/0006-291x(83)90562-4.
Forskolin at 25-100 microM elicited 10- to 15-fold stimulation of rabbit luteal adenylyl cyclase activity in the absence of guanine nucleotides. Addition of saturating concentrations of GTP or guanyl-5'-yl imidodiphosphate [GMP-P(NH)P] inhibited forskolin stimulation by 15-25% and 35-45%, respectively, in Na+-free media. The further addition of 8 microM [D-Ala2, Met5] enkephalin amide (Da-ENK) caused an additional 16-24% inhibition of activity in the presence of GTP plus forskolin, but did not alter enzymatic activity in the presence of forskolin alone or forskolin plus GMP-P(NH)P. Inhibition by guanine nucleotide alone or Da-ENK plus GTP was only observed in the presence of forskolin. Maximal inhibition by Da-ENK was observed at 25 microM forskolin. Da-ENK reduced the IC50 for GTP by 2.3-fold but did not alter the IC50 for GMP-P(NH)P. Addition of Na+ above 3 mM attenuated the inhibitory responses to GTP and GTP plus Da-ENK, but not to GMP-P(NH)P or GMP-P(NH)P plus Da-ENK. Above 100 mM, Na+ inhibited enzymatic activity in the presence of forskolin, forskolin plus GTP and forskolin plus GMP-P(NH)P in the absence and presence of Da-ENK. These findings suggest that the rabbit corpus luteum contains an inhibitory receptor for opiate peptides that couples to adenylyl cyclase.
在不存在鸟嘌呤核苷酸的情况下，25 - 100微摩尔的福斯高林能使兔黄体腺苷酸环化酶活性提高10至15倍。在无钠培养基中，加入饱和浓度的GTP或鸟苷 - 5'-基亚氨基二磷酸 [GMP-P(NH)P] 分别使福斯高林刺激作用抑制15 - 25% 和35 - 45%。进一步加入8微摩尔的 [D - Ala2, Met5] 脑啡肽酰胺（Da-ENK）在GTP加福斯高林存在时会使活性额外抑制16 - 24%，但在仅存在福斯高林或福斯高林加GMP-P(NH)P时不改变酶活性。仅在存在福斯高林时观察到单独鸟嘌呤核苷酸或Da-ENK加GTP的抑制作用。在25微摩尔福斯高林时观察到Da-ENK的最大抑制作用。Da-ENK使GTP的IC50降低2.3倍，但不改变GMP-P(NH)P的IC50。加入高于3毫摩尔的Na +会减弱对GTP和GTP加Da-ENK的抑制反应，但对GMP-P(NH)P或GMP-P(NH)P加Da-ENK无影响。高于100毫摩尔时，Na +在不存在和存在Da-ENK的情况下，在福斯高林、福斯高林加GTP和福斯高林加GMP-P(NH)P存在时抑制酶活性。这些发现表明兔黄体含有一种与腺苷酸环化酶偶联的阿片肽抑制性受体。
