Revis N W
J Histochem Cytochem. 1979 Oct;27(10):1322-6. doi: 10.1177/27.10.512318.
Previous investigators have shown that prefixation and lead staining completely inhibit the activity of adenylate cyclase. Lead has also been shown to stimulate the nonenzymatic hydrolysis of AMP-PMP (the substrate for adenylate cyclase) after 30 min incubation. The present studies were performed to determine if the omission of prefixation would provide a better method for localizing adenylate cyclase in cardiac muscle. These studies were also performed to determine the effect of short incubation on the lead-induced nonenzymatic hydrolysis of AMP-PNP. In prefixed sections the reaction product was diffusely localized over the section. However, in unfixed sections the reaction product appeared only on the sarcolemma and sarcotubule system. Results are presented showing that short incubation (i.e., 5 min) prevents the nonenzymatic hydrolysis of AMP-PMP by lead. In biochemical studies lead (10(-3) M) was shown to completely inhibit the activity of this enzyme. However, in the presence of 4 micrograms phosphatidylinositol, lead inhibition of this enzyme was reduced to 50% of the control value. Based on this observation, it is suggested that approximately 50% of adenylate cyclase is present in sections of cardiac muscle exposed to 2 x 10(-3) M lead, which is presumably enough activity for demonstration of adenylate cyclase activity.
先前的研究人员已经表明，预固定和铅染色会完全抑制腺苷酸环化酶的活性。研究还表明，孵育30分钟后，铅会刺激AMP-PMP（腺苷酸环化酶的底物）的非酶促水解。进行本研究以确定省略预固定是否能提供一种更好的方法来定位心肌中的腺苷酸环化酶。这些研究还旨在确定短时间孵育对铅诱导的AMP-PNP非酶促水解的影响。在预固定的切片中，反应产物弥散地分布在切片上。然而，在未固定的切片中，反应产物仅出现在肌膜和肌小管系统上。结果表明，短时间孵育（即5分钟）可防止铅对AMP-PMP的非酶促水解。在生化研究中，铅（10⁻³ M）被证明能完全抑制该酶的活性。然而，在存在4微克磷脂酰肌醇的情况下，铅对该酶的抑制作用降至对照值的50%。基于这一观察结果，有人提出，暴露于2×10⁻³ M铅的心肌切片中约50%的腺苷酸环化酶存在，这可能具有足够的活性来证明腺苷酸环化酶的活性。
