Nikula H, Huhtaniemi I
Department of Physiology, University of Turku, Finland.
Acta Endocrinol (Copenh). 1989 Sep;121(3):327-33. doi: 10.1530/acta.0.1210327.
The role of protein kinase C in modulation of the endocrine function of rat Leydig cells was studied. Percoll-purified rat Leydig cells were stimulated with hCG, forskolin, cholera toxin, pertussis toxin and 8-bromo-cAMP in the presence and absence of two activators of protein kinase C, 12-0-tetradecanoylphorbol 13-acetate (TPA) or 1-oleoyl-2-acetyl-sn-glycerol (OAG). The two activators had no effect on basal cAMP, but decreased hCG-stimulated, and increased cholera toxin- and forskolin-stimulated cAMP production. Cells pre-incubated with pertussis toxin showed enhanced rate of cAMP production in response to forskolin, but were no more responsive to TPA and OAG stimulation. These findings suggest that protein kinase C activation may on one hand inhibit the LH-receptor and Gs-protein coupling and on the other hand inhibit the Gi-protein mediated suppression of adenylyl cyclase activity. TPA and OAG effects on testosterone production were measured in the absence and presence of 8-bromo-cAMP stimulation. TPA enhanced basal testosterone production, but this effect was shifted to inhibition when steroidogenesis was stimulated by 8-bromo-cAMP. The OAG effect on testosterone production was inhibitory throughout the dose-response curve of 8-bromo-cAMP. The basal stimulation of testosterone production by TPA was probably due to a marginal increase of cAMP caused by inhibition of the Gi-protein, since a similar effect was observed by pertussis toxin, and thereafter TPA was without effect on testosterone. The inhibition of stimulated testosterone production by TPA and OAG indicates that protein kinase C activity also affects steroidogenesis at a step(s) beyound cAMP formation.
研究了蛋白激酶C在调节大鼠睾丸间质细胞内分泌功能中的作用。在存在和不存在两种蛋白激酶C激活剂，即12 - O - 十四烷酰佛波醇13 - 乙酸酯（TPA）或1 - 油酰 - 2 - 乙酰 - sn - 甘油（OAG）的情况下，用hCG、福斯高林、霍乱毒素、百日咳毒素和8 - 溴 - cAMP刺激经Percoll纯化的大鼠睾丸间质细胞。这两种激活剂对基础cAMP无影响，但降低了hCG刺激的cAMP生成，并增加了霍乱毒素和福斯高林刺激的cAMP生成。预先用百日咳毒素孵育的细胞对福斯高林刺激的cAMP生成速率增强，但对TPA和OAG刺激不再有反应。这些发现表明，蛋白激酶C激活一方面可能抑制LH受体和Gs蛋白偶联，另一方面可能抑制Gi蛋白介导的腺苷酸环化酶活性抑制。在不存在和存在8 - 溴 - cAMP刺激的情况下，测量了TPA和OAG对睾酮生成的影响。TPA增强了基础睾酮生成，但当8 - 溴 - cAMP刺激类固醇生成时，这种作用转变为抑制。在8 - 溴 - cAMP的整个剂量反应曲线中，OAG对睾酮生成的作用都是抑制性的。TPA对睾酮生成的基础刺激可能是由于Gi蛋白抑制导致cAMP略有增加，因为百日咳毒素也观察到类似的作用，此后TPA对睾酮没有影响。TPA和OAG对刺激的睾酮生成的抑制表明，蛋白激酶C活性在cAMP形成之外的一个或多个步骤也影响类固醇生成。
