Müller-Suur R, Gutsche H U
Karolinska Institutet, Danderyd Hospital, Stockholm, Sweden.
J Nucl Med. 1995 Sep;36(9):1654-8.
Intrarenal handling of 99mTc-DMSA is still controversial, particularly in the existence of tubular reabsorption from the tubular fluid. Experiments were performed with micropuncture technique on the rat kidney in an attempt to elucidate this question.
The concentration profile of 99mTc-DMSA along the nephron was measured in fluid from Bowman's space of surface glomeruli and from the proximal and distal tubules collected by micropuncture. Superficial loops of proximal tubules were micropunctured and microperfused with 99mTc-DMSA or [99mTc] pertechnetate for 10 or 20 min at physiological flow rates; the recovery of activity was measured in the final urine.
Bowman's space urine contained only 14% of the 99mTc activity of arterial plasma, indicating low filtration of 99mTc-DMSA, likely due to high plasma protein binding. Tubular fluid-to-plasma activity ratios of 0.31 in the proximal tubules and 1.31 in the distal tubules suggest that 99mTc-DMSA is neither secreted nor reabsorbed along the nephron. Ninety-eight percent of the 99mTc-DMSA activity was recovered in the final ipsilateral urine, while only 0.5% was found in the urine of the contralateral kidney.
A low fraction of 99mTc-DMSA enters the tubule by glomerular filtration and is not reabsorbed from the tubular fluid. Thus, only peritubular extraction by the tubular cell is responsible for renal uptake of 99mTc-DMSA.
99mTc-DMSA在肾内的处理仍存在争议，特别是在肾小管液存在肾小管重吸收的情况下。为了阐明这个问题，我们用微穿刺技术对大鼠肾脏进行了实验。
通过微穿刺测量了99mTc-DMSA在肾小体Bowman囊腔、近端小管和远端小管液中的浓度分布。对近端小管浅表袢进行微穿刺，并以生理流速用99mTc-DMSA或高锝酸盐灌注10或20分钟；测量最终尿液中的放射性回收率。
Bowman囊腔尿液中仅含动脉血浆99mTc活性的14%，表明99mTc-DMSA滤过率低，可能是由于血浆蛋白结合率高。近端小管的肾小管液与血浆活性比为0.31，远端小管为1.31，这表明99mTc-DMSA在整个肾单位中既不分泌也不重吸收。99mTc-DMSA活性的98%在同侧最终尿液中回收，而对侧肾脏尿液中仅发现0.5%。
一小部分99mTc-DMSA通过肾小球滤过进入小管，且不从小管液中重吸收。因此，99mTc-DMSA的肾脏摄取仅由肾小管细胞的周缘摄取负责。
