Lindeman K S, Hirshman C A, Kuhl J S, Levitsky H I, Emala C W
Department of Anesthesiology/Critical Care Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21205, USA.
Biol Reprod. 1998 Nov;59(5):1108-15. doi: 10.1095/biolreprod59.5.1108.
To determine whether chronic oxytocin pretreatment inhibits adenylyl cyclase, we compared adenylyl cyclase activity in membranes prepared from cultured, immortalized rat myometrial cells that were untreated or pretreated for 24 h with oxytocin. Chronic oxytocin pretreatment (1 x 10(-5) M for 24 h) attenuated basal, guanosine triphosphate (1 x 10(-5) M)-, isoproterenol (1 x 10(-4) M)-, forskolin (1 x 10(-5) M)-, MnCl2 (20 mM)- or NaF (1 x 10(-2) M)-stimulated adenylyl cyclase activity by 27 +/- 5% to 39 +/- 11% (n = 6, p < 0.05). Oxytocin pretreatment for 2 h (n = 5) did not produce a significant effect. To understand the mechanism by which oxytocin pretreatment decreased activity of the adenylyl cyclase pathway, we compared effects of pretreatment with either oxytocin or phenylephrine on adenylyl cyclase activity and determined the effects of Gi inhibition and protein kinase C (PKC) depletion. Chronic (24 h) phenylephrine pretreatment (1 x 10(-4) M) had effects similar to those of oxytocin pretreatment (1 x 10(-5) M). PKC depletion with phorbol 12-myristate 13-acetate (1 x 10(-6) M, 41 h) prevented attenuation of adenylyl cyclase activity by oxytocin pretreatment (1 x 10(-5) M for 24 h). Inhibition of Gi by pertussis toxin pretreatment (1.25 microg/ml, 41 h) had no significant effect. These findings suggest that chronic oxytocin pretreatment desensitizes the adenylyl cyclase pathway by a cross-regulatory mechanism that involves activation of Gq and PKC.
为了确定慢性催产素预处理是否会抑制腺苷酸环化酶，我们比较了从培养的、永生化大鼠子宫肌层细胞制备的膜中腺苷酸环化酶的活性，这些细胞未处理或用催产素预处理24小时。慢性催产素预处理（1×10⁻⁵ M，持续24小时）使基础的、三磷酸鸟苷（1×10⁻⁵ M）、异丙肾上腺素（1×10⁻⁴ M）、福斯可林（1×10⁻⁵ M）、氯化锰（20 mM）或氟化钠（1×10⁻² M）刺激的腺苷酸环化酶活性降低了27±5%至39±11%（n = 6，p < 0.05）。催产素预处理2小时（n = 5）未产生显著影响。为了理解催产素预处理降低腺苷酸环化酶途径活性的机制，我们比较了催产素或去氧肾上腺素预处理对腺苷酸环化酶活性的影响，并确定了Gi抑制和蛋白激酶C（PKC）耗竭的作用。慢性（24小时）去氧肾上腺素预处理（1×10⁻⁴ M）的作用与催产素预处理（1×10⁻⁵ M）相似。用佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯（1×10⁻⁶ M，41小时）耗竭PKC可防止催产素预处理（1×10⁻⁵ M，持续24小时）导致的腺苷酸环化酶活性降低。百日咳毒素预处理（1.25微克/毫升，41小时）抑制Gi没有显著影响。这些发现表明，慢性催产素预处理通过涉及Gq和PKC激活的交叉调节机制使腺苷酸环化酶途径脱敏。
