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首页> 外文期刊>American Journal of Physiology >Modulation by dietary sodium intake of melanocortin 3 receptor mRNA and protein abundance in the rat kidney.
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Modulation by dietary sodium intake of melanocortin 3 receptor mRNA and protein abundance in the rat kidney.

机译：饮食中大鼠肾脏中黑皮质素3受体mRNA和蛋白质丰度的钠摄入量调节。

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摘要

Gamma-melanocyte stimulating hormone (gamma-MSH) is a circulating natriuretic peptide hormone derived from proopiomelanocortin (POMC); its concentration in plasma and pituitary POMC mRNA abundance, increase in rats ingesting a high-sodium diet (HSD, 8% NaCl) compared with a low-sodium diet (LSD, 0.07% NaCl). RT-PCR of rat kidney RNA demonstrated reaction products of the expected size in both cortex and medulla for MC3-R, MC4-R, and MC5-R mRNA; no signal for MC1-R or MC2-R was detected. Relative to beta-actin or cyclophilin, abundance of the three receptor transcripts after 1 wk of the LSD was approximately equal in both cortex and medulla. After 1 wk of the HSD, mRNA abundance of MC4-R and MC5-R was unchanged, whereas that of MC3-R in medulla more than doubled, the ratio of MC3-R/beta-actin signal increasing from 0.38 +/- 0.04 on LSD to 0.84 +/- 0.04 on HSD (P < 0.001). No significant increase occurred in the cortex. The increase in MC3-R expression induced by dietary sodium was observed in inner medullary collecting duct (IMCD) cells isolated from the kidneys of HSD rats, suggesting that these cells were the major site of receptor expression in the medulla. Immunoblots of whole medullary and IMCD cell homogenates detected MC3-R immunoreactive protein; its expression was twice as great in samples from HSD vs. LSD rat kidneys, paralleling the increase in MC3-R mRNA abundance on the HSD. No changes in MC4-R or MC5-R protein expression were observed. Incubation of IMCD cell suspensions with increasing concentrations of gamma2-MSH led to increased cAMP accumulation, with values from rats on the HSD being roughly double the values from LSD rats. Intrarenal infusion of gamma2-MSH (500 fmol/min) increased sodium and cAMP excretion from the infused but not contralateral kidney of HSD rats, while having no effect in LSD rats. These data show that MC3-R is expressed in rat IMCD cells in a manner modulated by dietary sodium intake. Because MC3-R is the receptor with which gamma-MSH interacts, our findings suggest the existence of a sodium-regulating system, activated in response to a HSD, which increases urinary sodium excretion to balance the high-sodium intake.
机译：γ-黑素细胞刺激激素（gamma-MSH）是一种循环的利钠肽激素，源自proopiomelanocortin（POMC）;与低钠饮食（LSD，0.07％NaCl）相比，高钠饮食（HSD，8％NaCl）的大鼠血浆和垂体POMC mRNA丰度升高。大鼠肾RNA的RT-PCR证实了皮质和髓质中针对MC3-R，MC4-R和MC5-R mRNA的预期大小的反应产物。未检测到MC1-R或MC2-R的信号。相对于β-肌动蛋白或亲环蛋白，LSD 1周后三个受体转录物的丰度在皮质和延髓中均大致相等。在HSD 1周后，MC4-R和MC5-R的mRNA丰度保持不变，而髓质中MC3-R的mRNA丰度增加了一倍以上，MC3-R /β-肌动蛋白信号的比率从0.38 +/- 0.04增加在LSD上为0.84 +/- 0.04（在HSD上）（P <0.001）。皮质没有明显增加。在从HSD大鼠肾脏分离的内髓收集管（IMCD）细胞中观察到饮食钠诱导的MC3-R表达增加，表明这些细胞是髓质受体表达的主要部位。全髓和IMCD细胞匀浆的免疫印迹检测到MC3-R免疫反应蛋白;其表达在HSD大鼠肾脏样品中是LSD大鼠肾脏的两倍，与HSD中MC3-R mRNA丰度的增加平行。没有观察到MC4-R或MC5-R蛋白表达的变化。随着浓度增加的gamma2-MSH孵育IMCD细胞悬液导致cAMP积累增加，HSD上大鼠的值大约是LSD大鼠值的两倍。肾内输注gamma2-MSH（500 fmol / min）增加了HSD大鼠输注但非对侧肾脏的钠和cAMP排泄，而对LSD大鼠则无作用。这些数据表明，MC3-R在大鼠IMCD细胞中的表达受饮食钠摄入量的调节。因为MC3-R是与γ-MSH相互作用的受体，所以我们的发现表明存在一个钠调节系统，该系统可响应HSD激活，从而增加尿钠排泄以平衡高钠摄入量。

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