Wideman R F, Clark N B, Braun E J
Am J Physiol. 1980 Sep;239(3):F233-43. doi: 10.1152/ajprenal.1980.239.3.F233.
The effects of phosphate loading were examined in intact, parathyroidectomized (PTX), and PTX starlings infused with parathyroid extract (PTX +/- PTE). In intact starlings, there was no correlation between the filtered phosphate load and the quantity of phosphate excreted. Net secretion predominated at lower filtered loads (2.5-20 mu mol . kg-1 . min-1) but net reabsorption occurred at filtered loads between 20 and 35 mu mol . kg-1 . min-1. Phosphate-loaded PTX starlings reabsorb phosphate over a wide range of filtered loads (5-45 mu mol . kg-1 . min-1). Excretion was significantly correlated with the filtered load in PTX birds (r = 0.943). Phosphate loaded PTX + PTE starlings secreted phosphate when filtered loads ranged from 2.5 to 30 mu mol . kg-1 . min-1. Excretion also was significantly correlated with the filtered load in this group (r = 0.972). The results of these experiments indicate that a) variations in endogenous PTH release in intact starlings result in wide variations in the renal pattern of phosphate excretion during phosphate loading; b) net phosphate secretion rarely occurs during phosphate loading in PTX starlings, but always occurs in PTX + PTE starlings; and c) both phosphate secretion and phosphate reabsorption are limited by maximal tubular transport capacities. Additional evidence indicates that PTH inhibits tubular phosphate reabsorption in starlings.
在完整的、甲状旁腺切除的（PTX）以及注入甲状旁腺提取物的甲状旁腺切除的（PTX +/- PTE）欧椋鸟中研究了磷酸盐负荷的影响。在完整的欧椋鸟中，滤过的磷酸盐负荷与排泄的磷酸盐量之间没有相关性。在较低的滤过负荷（2.5 - 20 μmol·kg⁻¹·min⁻¹）时净分泌占主导，但在20至35 μmol·kg⁻¹·min⁻¹的滤过负荷时发生净重吸收。磷酸盐负荷的PTX欧椋鸟在很宽的滤过负荷范围（5 - 45 μmol·kg⁻¹·min⁻¹）内重吸收磷酸盐。PTX鸟的排泄与滤过负荷显著相关（r = 0.943）。当滤过负荷范围为2.5至30 μmol·kg⁻¹·min⁻¹时，磷酸盐负荷的PTX + PTE欧椋鸟分泌磷酸盐。该组的排泄也与滤过负荷显著相关（r = 0.972）。这些实验结果表明：a）完整欧椋鸟体内内源性甲状旁腺激素（PTH）释放的变化导致磷酸盐负荷期间肾脏磷酸盐排泄模式的广泛变化；b）PTX欧椋鸟在磷酸盐负荷期间很少发生净磷酸盐分泌，但PTX + PTE欧椋鸟总是发生净磷酸盐分泌；c）磷酸盐分泌和磷酸盐重吸收都受到最大肾小管转运能力的限制。额外的证据表明PTH抑制欧椋鸟肾小管对磷酸盐的重吸收。
