Johnson V, Spitzer A
Am J Physiol. 1986 Aug;251(2 Pt 2):F251-6. doi: 10.1152/ajprenal.1986.251.2.F251.
The isolated perfused kidney of the guinea pig has been used to assess the mechanism that accounts for the maintenance of the positive phosphate (Pi) balance during development. The kidneys obtained from mature guinea pigs (n = 25) had a glomerular filtration rate (GFR) of 0.48 +/- 0.04 ml/min (mean +/- SE), whereas those of the newborn (n = 20) had a GFR of 0.15 +/- 0.02 ml/min. These values compare favorably with those observed in intact animals. The fractional excretion of Na+ (FENa) was 3.8 +/- 0.7% in the mature kidneys and 4.7 +/- 0.7% in the newborn kidneys. The maximal tubular reabsorption of Pi (TmPi) by the newborn kidney was 24.3 +/- 2.8 micrograms/min. The filtered load at which the TmPi of the newborn was reached exceeds by 2.5-fold the filtered load of Pi encountered under physiological conditions. In the adult the TmPi was 53.9 +/- 2.6 micrograms/min. The filtered load at which the TmPi of the adult was reached is only slightly higher than the average normal filtered load of Pi. The TmPi/GFR was significantly higher (P less than 0.02) in the newborn (117.4 +/- 10.8 micrograms X min-1 X ml-1 GFR) compared with the adult (82.6 +/- 3.6 micrograms X min-1 X ml-1 GFR). Moreover, at any filtered load of Pi below Tm the newborn animals reabsorbed twofold more Pi per gram kidney weight than the adult (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
豚鼠的离体灌流肾脏已被用于评估在发育过程中维持正磷酸盐（Pi）平衡的机制。从成年豚鼠（n = 25）获得的肾脏肾小球滤过率（GFR）为0.48±0.04 ml/分钟（平均值±标准误），而新生豚鼠（n = 20）的GFR为0.15±0.02 ml/分钟。这些值与在完整动物中观察到的值相当。成年肾脏中Na+的分数排泄（FENa）为3.8±0.7%，新生肾脏中为4.7±0.7%。新生肾脏对Pi的最大肾小管重吸收（TmPi）为24.3±2.8微克/分钟。达到新生肾脏TmPi时的滤过负荷比生理条件下遇到的Pi滤过负荷高出2.5倍。成年动物的TmPi为53.9±2.6微克/分钟。达到成年动物TmPi时的滤过负荷仅略高于Pi的平均正常滤过负荷。与成年动物（82.6±3.6微克·分钟-1·毫升-1 GFR）相比，新生动物（117.4±10.8微克·分钟-1·毫升-1 GFR）的TmPi/GFR显著更高（P<0.02）。此外，在任何低于Tm的Pi滤过负荷下，新生动物每克肾脏重量重吸收的Pi比成年动物多两倍（P<0.01）。（摘要截断于250字）
