Cho K W, Kim S H, Seul K H, Hwang Y H, Kook Y J
Department of Physiology, Jeonbug National University Medical School, Jeonju, South Korea.
Regul Pept. 1994 Jul 14;52(2):129-37. doi: 10.1016/0167-0115(94)90045-0.
Employing isolated perfused rabbit atrial model we have found that stretch-activated atrial natriuretic peptide (ANP) secretion takes place in two steps: release of ANP from myocytes into surrounding intercellular space, and then translocation of the released ANP into atrial lumen along with the extracellular fluid (ECF) translocated upon releasing the stretch. Ca2+, one of the most important factors regulating secretory processes, has been reported by many workers to have influence on the ANP secretion, but at large variance. In the present study, therefore, we undertook to clarify the influence of Ca2+ depletion on ANP secretion and further to define which of the two steps is affected by Ca2+ removal. Extracellular Ca2+ depletion resulted in increased basal secretion and in accentuated secretion of immunoreactive (ir) ANP in response to mechanical stimuli. The translocation of ECF increased in response to atrial stretch-and-release, but it was not affected by Ca2+ depletion. The irANP concentration in the extracellular space calculated as the amount of irANP secreted in relation to the ECF translocated significantly increased when extracellular Ca2+ was depleted. These results indicate that extracellular Ca2+ depletion accentuates the stretch-induced ANP secretion through the augmentation of ANP release into the interstitium without changes in the ECF translocation.
利用离体灌注兔心房模型，我们发现牵张激活的心房利钠肽（ANP）分泌分两步进行：ANP从心肌细胞释放到周围细胞间隙，然后随着牵张释放时细胞外液（ECF）的转运，释放的ANP转运至心房腔。钙离子是调节分泌过程的最重要因素之一，许多研究人员报道其对ANP分泌有影响，但差异很大。因此，在本研究中，我们致力于阐明钙离子耗竭对ANP分泌的影响，并进一步确定钙离子去除影响这两个步骤中的哪一步。细胞外钙离子耗竭导致基础分泌增加以及对机械刺激的免疫反应性（ir）ANP分泌增强。ECF的转运在心房牵张-释放时增加，但不受钙离子耗竭的影响。当细胞外钙离子耗竭时，以相对于转运的ECF分泌的irANP量计算的细胞外空间中irANP浓度显著增加。这些结果表明，细胞外钙离子耗竭通过增加ANP向间质的释放而不改变ECF转运，从而增强牵张诱导的ANP分泌。
