AJP - Renal Physiology, Vol 251, Issue 5 822-F830, Copyright © 1986 by American Physiological Society
Handling of lysozyme in isolated perfused proximal tubules
J. T. Nielsen, S. Nielsen and E. I. Christensen
Isolated, perfused proximal tubules from rabbit were used to study the
luminal endocytic uptake, digestion, and transcellular transport of
125I-lysozyme. Ten tubules were perfused for 20 min with 125I-lysozyme and
[14C]inulin and then with tracer-free perfusate for additional 40 min
before fixation. The uptake and digestion of lysozyme was calculated per
millimeter tubule length. The transfer of intact lysozyme from perfusate to
the bath was measured and compared with the transfer of inulin. Five
tubules were processed for electron microscope autoradiography, and the
grain distribution was analyzed quantitatively. The results show that 2.7%
of the perfused amount of lysozyme was taken up, and 21.3% of the absorbed
protein was digested. The present experiments demonstrate that the transfer
of intact lysozyme from lumen to bath is not significantly different from
the transfer of inulin. The autoradiographic analysis showed that lysozyme
was localized mainly in endocytic vacuoles and lysosomes after 60 min of
perfusion.
