Schjoldager B, Park J, Johnsen A H, Yamada T, Rehfeld J F
Department of Medical Physiology, Rigshospitalet, University of Copenhagen, Denmark.
Am J Physiol. 1991 Jun;260(6 Pt 1):G976-82. doi: 10.1152/ajpgi.1991.260.6.G977.
The protochordean octapeptide cionin is structurally a hybrid of mammalian cholecystokinin (CCK) and gastrin, and thus their possible common ancestor. To determine whether cionin behaves like CCK or gastrin, we examined its effect on canine fundic somatostatin cells and on porcine and bovine gallbladder muscles. Cionin released somatostatin with a potency (ED50 0.15 nM) and efficacy (14.8% of cell content) similar to that of CCK-8 (ED50 0.12 nM, efficacy 16.7%). The efficacies but not the potencies of CCK-8 and cionin differed from those of sulfated gastrin (0.12 nM, 9.7%), nonsulfated gastrin (0.20 nM, 9.4%), and nonsulfated CCK-8 (0.30 nM, 10.4%). CCK and gastrin stimulated contractions of porcine gallbladder muscle strips in a concentration-dependent manner with no differences in efficacy but with characteristic differences in potency. CCK-8 and cionin displayed similar potencies of ED50 2.0 and 2.6 nM; both were significantly different from the ED50 of 0.4 microM for sulfated gastrin and 2.3 microM for nonsulfated gastrin. CCK radioligand binding to membrane-enriched preparations of porcine and bovine gallbladder muscularis was specific and of high affinity. The equilibrium data revealed that binding of CCK and gastrin peptides best fit a single site. CCK-8 and cionin displayed similar affinities [Kd 0.5 nM (porcine), 0.5 nM (bovine, CCK) vs. Kd 0.8 and 0.9 nM (cionin), respectively]. These differed again significantly from Kd 0.6 and 1.5 microM (sulfated gastrin) and 0.7 and 0.2 microM (nonsulfated gastrin). The results show that cionin behaves like CCK rather than gastrin in mammals.
原索动物八肽cionin在结构上是哺乳动物胆囊收缩素（CCK）和胃泌素的杂交体，因此可能是它们的共同祖先。为了确定cionin的行为是否类似于CCK或胃泌素，我们研究了其对犬胃底生长抑素细胞以及猪和牛胆囊肌肉的影响。Cionin释放生长抑素的效力（ED50为0.15 nM）和效能（占细胞含量的14.8%）与CCK-8（ED50为0.12 nM，效能为16.7%）相似。CCK-8和cionin的效能而非效力与硫酸化胃泌素（0.12 nM，9.7%）、非硫酸化胃泌素（0.20 nM，9.4%）和非硫酸化CCK-8（0.30 nM，10.4%）不同。CCK和胃泌素以浓度依赖性方式刺激猪胆囊肌肉条的收缩，效能无差异，但效力有特征性差异。CCK-8和cionin的效力相似，ED50分别为2.0和2.6 nM；两者均与硫酸化胃泌素的ED50（0.4 microM）和非硫酸化胃泌素的ED50（2.3 microM）有显著差异。CCK放射性配体与猪和牛胆囊肌层富含膜的制剂的结合是特异性的且具有高亲和力。平衡数据显示，CCK和胃泌素肽的结合最符合一个位点。CCK-8和cionin显示出相似的亲和力[Kd分别为0.5 nM（猪）、0.5 nM（牛，CCK）与Kd 0.8和0.9 nM（cionin）]。这些又与Kd 0.6和1.5 microM（硫酸化胃泌素）以及0.7和0.2 microM（非硫酸化胃泌素）有显著差异。结果表明，在哺乳动物中cionin的行为类似于CCK而非胃泌素。
