Physiological role of atrial natriuretic polypeptides on lactation

ICR小鼠出生后血浆A型心钠素(ANP)浓度显著高于妊娠期和处女对照组。持续升高至哺乳期第15天(L15)。出生当天，心肌细胞ANP免疫反应性(IR)和ANP颗粒数较妊娠期和处女对照组有所下降，然后开始持续升高，直到第15天。本研究结果提示ANP在哺乳期可能起重要作用，提示ANP的合成和释放较为活跃。分娩当天，催产素(OX)被释放。因此，我们得出一个假设，OX可能在分娩时和哺乳期刺激ANP的释放，ANP的释放可能通过乳腺受体影响乳腺功能。关于ANP家族多肽的进化，与人ANP或B型ANP(BNP)相比，鳗鱼V型ANP(VNP)在犬冠状动脉中表现出较强的血管扩张活性，提示该分子可能存在于哺乳动物中。在进化过程中，ANP家族多肽可能在哺乳动物中具有新的作用，除了它们的保守作用外，还作为一种控制乳腺功能的活动。此外，还研究了最近从人中发现的鱼源性多肽-肾上腺髓质素-2对猪冠状动脉的扩张反应。对目前关于垂体-心房-乳腺轴的假说有进一步研究的必要，特别是从进化的角度。

Plasma A-type atrial natriuretic peptide(ANP) concentration after delivery in ICR mice was significantly higher than those during pregnancy and in virgin controls. It continued to increase until the 15th day of lactation (L15). On the day of delivery, ANP- immunoreactivity(IR) and the number of ANP-granules in the cardiocytes decreased compared to those during pregnancy and to those in virgin controls, and then they both began to increase continually until L15. The present results may suggest the significant role of ANP during lactation, suggesting active synthesis and release of ANP. On the day of delivery, Oxytocin(OX) is released. Thus, we get a hypothesis that OX may stimulate ANP release at the delivery and during the lactation and released ANP may affect mammary function through the receptors in the mammary gland. Concerning the evolution of ANP family peptides, eel V-type ANP (VNP) showed potent vasodilatory activity in canine coronary artery compared with human ANP or B-type ANP (BNP), suggesting a possible occurrence of this molecule in the mammals. During evolution, ANP family peptides may have a novel role in mammals as a control activity on mammary function in addition to their conservative role. In addition, vasodilatory response of a fish-origin peptide found recently from human, adrenomedullin 2 in porcine coronary artery was also studied. Further studies on the present hypothesis on pituitary-atrium-mammary gland axis are necessary especially from evolutional aspect.