Ross C R, Diezi-Chomety F, Roch-Ramel F
Am J Physiol. 1975 Jun;228(6):1641-5. doi: 10.1152/ajplegacy.1975.228.6.1641.
The renal excretion of N'1-methylnicotinamide (NMN) was studied in the rat. Renal clearance experiments clearly demonstrated that: 1) NMN is secreted; 2)a tubularmaximum (Tm), 7 mumol/min per kg, could be reached; and 3)NMN secretion is inhibitedby a competitive inhibitor, mepiperphenidol. In free-flow micropuncture experiments, animals were infused with plasma concentrations of NMN ABOVE Tm; the TF/P NMNto TF/P inblin ratio for proximal and distal samples was 2.34 and 2.28, respectively, indicating that NMN is secreted in the proximal tubules and is not secreted orreabsorbed in the distal tubules. This finding was further confirmed by intratubularmicroinjections of ['14C]NMN into rats. In diuretic animals approxiamately 10%of the NMN injected into early proximal tubules was reabsorbed, but no reabsorption could be detected after distal injections. The nondiuretic animals showed no significant reabsorption of NMN. It was concluded that NMN transport is a carrier-mediated process and that reabsorption, if it occurs, plays only a minor role.
对大鼠体内N'-1-甲基烟酰胺（NMN）的肾排泄进行了研究。肾清除实验清楚地表明：1）NMN是被分泌的；2）可达到每千克每分钟7微摩尔的肾小管最大分泌率（Tm）；3）NMN的分泌受到竞争性抑制剂美哌隆的抑制。在自由流动微穿刺实验中，给动物输注高于Tm的血浆浓度的NMN；近端和远端样本的TF/P NMN与TF/P 肌酐比值分别为2.34和2.28，表明NMN在近端小管中被分泌，而在远端小管中既不被分泌也不被重吸收。将[¹⁴C]NMN经肾小管内微注射到大鼠体内，进一步证实了这一发现。在利尿动物中，注入早期近端小管的NMN约有10%被重吸收，但远端注射后未检测到重吸收。非利尿动物未显示出NMN有明显的重吸收。得出的结论是，NMN的转运是一个载体介导的过程，并且重吸收（如果发生的话）仅起次要作用。
