Guntupalli J, Delaney V, Weinman E J, Lyle D, Allon M, Bourke E
Department of Medicine, University of Texas Medical School, Houston 77025.
Am J Physiol. 1991 Aug;261(2 Pt 2):F227-37. doi: 10.1152/ajprenal.1991.261.2.F227.
The effects of maleic acid on renal phosphate (Pi) transport were examined by clearance and brush-border membrane vesicle (BBMV) transport studies. In normal rats, maleic acid 50 mg.kg body wt-1.h-1 increased the phosphaturia (P less than 0.001). Intraperitoneal administration of a similar dose of maleic acid decreased the BBMV uptake of Pi but not glucose. In rats fed a low-phosphate diet (0.03%), the maleic acid-induced phosphaturia was blunted, but the inhibitory effect on the BBMV transport of Pi persisted. In chronic parathyroidectomized rats fed a low-phosphate diet, where the filtered load of Pi was higher than in the previous groups, the phosphaturia was abolished, but the inhibition of the BBMV transport of Pi was sustained. Both the in vitro incubation of BBMVV and in vivo administration of maleic acid were associated with a competitive inhibition of Pi transport. These studies indicate that the maleic acid-induced phosphaturia is expressed at the apical membrane entry step of Pi, and the enhanced distal tubular reabsorption accounts for the lack of phosphaturia in dietary Pi deprivation.
通过清除率和刷状缘膜囊泡（BBMV）转运研究，检测了马来酸对肾磷酸盐（Pi）转运的影响。在正常大鼠中，马来酸50mg·kg体重-1·h-1可增加磷酸盐尿（P<0.001）。腹腔注射相似剂量的马来酸可降低BBMV对Pi的摄取，但不影响葡萄糖的摄取。在喂食低磷饮食（0.03%）的大鼠中，马来酸诱导的磷酸盐尿减弱，但对BBMV Pi转运的抑制作用仍然存在。在喂食低磷饮食的慢性甲状旁腺切除大鼠中，Pi的滤过负荷高于先前各组，磷酸盐尿消失，但对BBMV Pi转运的抑制作用持续存在。BBMV的体外孵育和马来酸的体内给药均与Pi转运的竞争性抑制有关。这些研究表明，马来酸诱导的磷酸盐尿在Pi的顶端膜进入步骤中表现出来，而远端肾小管重吸收增强是饮食中Pi缺乏时磷酸盐尿缺乏的原因。
