Matozaki T, Sakamoto C, Nagao M, Baba S
Nihon Naibunpi Gakkai Zasshi. 1986 Jul 20;62(7):807-17. doi: 10.1507/endocrine1927.62.7_807.
To clarify the precise mechanism by which unrelated peptides, cholecystokinin or carbamylcholine, modulate the somatostatin binding, the effect of a phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) or a synthetic diacylglycerol analog, 1-oleyl-2-acetylglycerol (OAG) on [125I-Tyr1]somatostatin binding to pancreatic acinar cell membranes was examined. Pretreatment of pancreatic acini for 120 min at 37 degrees C with 100 ng/ml TPA maximally reduced subsequent labeled somatostatin binding to acinar membranes. The inhibitory effect of TPA on the somatostatin binding was dependent on the dose used, or the time and temperature of pretreatment. These effects of TPA were almost mimicked by the treatment of acini with OAG. Scatchard analysis of [125I-Tyr1]somatostatin binding demonstrated that the decrease in the labeled somatostatin binding induced by TPA or OAG pretreatment was due to the decrease in the maximum binding capacity without a significant change in the binding affinity. A specifically labeled single band of the Mr = 90 K obtained with a photoaffinity cross-linking study indicates that the somatostatin binding sites are the same somatostatin receptor as previously described. Moreover, the intensity of the Mr = 90 K band was dramatically decreased when acini were treated with increasing concentrations of TPA, a finding consistent with TPA-induced decrease in binding capacity. Such an inhibitory effect of TPA was abolished when pretreatment of acini with TPA was performed in the presence of Ca2+ chelating compounds such as EDTA and EGTA. Interestingly, the combined treatment of TPA and Ca2+ ionophore A23187 caused synergistic inhibition of the subsequent labeled somatostatin binding to acinar membranes, although Ca2+ ionophore itself almost failed to affect the somatostatin binding. These results suggest, therefore, that TPA or OAG can modulate somatostatin binding to its receptors on rat pancreatic acinar cell membranes, presumably through activation of Ca2+-activated, phospholipid-dependent protein kinase (protein kinase C) and the activated protein kinase C and intracellular Ca2+ mobilization presumably act to modulate pancreatic acinar somatostatin receptors synergistically.
为阐明不相关的肽、胆囊收缩素或氨甲酰胆碱调节生长抑素结合的确切机制，研究了佛波酯12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA）或合成二酰基甘油类似物1 - 油酰 - 2 - 乙酰甘油（OAG）对[125I - Tyr1]生长抑素与胰腺腺泡细胞膜结合的影响。在37℃下用100 ng/ml TPA预处理胰腺腺泡120分钟，可最大程度降低随后标记的生长抑素与腺泡细胞膜的结合。TPA对生长抑素结合的抑制作用取决于所用剂量、预处理时间和温度。用OAG处理腺泡几乎可模拟TPA的这些作用。对[125I - Tyr1]生长抑素结合进行Scatchard分析表明，TPA或OAG预处理诱导的标记生长抑素结合减少是由于最大结合能力降低，而结合亲和力无显著变化。光亲和交联研究获得的一条Mr = 90K的特异性标记单带表明，生长抑素结合位点与先前描述的生长抑素受体相同。此外，当用浓度递增的TPA处理腺泡时，Mr = 90K条带的强度显著降低，这一发现与TPA诱导的结合能力降低一致。当在Ca2 +螯合化合物如EDTA和EGTA存在下用TPA预处理腺泡时，TPA的这种抑制作用被消除。有趣的是，TPA和Ca2 +离子载体A23187联合处理对随后标记的生长抑素与腺泡细胞膜的结合产生协同抑制作用，尽管Ca2 +离子载体本身几乎不影响生长抑素结合。因此，这些结果表明，TPA或OAG可能通过激活Ca2 +激活的磷脂依赖性蛋白激酶（蛋白激酶C）来调节生长抑素与大鼠胰腺腺泡细胞膜上其受体的结合，并且激活的蛋白激酶C和细胞内Ca2 +动员可能协同作用来调节胰腺腺泡生长抑素受体。
