AJP - Renal Physiology, Vol 256, Issue 1 13-F17, Copyright © 1989 by American Physiological Society
Correlation of structure and function in developing proximal tubule of guinea pig
L. W. Welling, A. P. Evan, V. H. Gattone 2nd, S. Rollins, R. Saunders, F. J. Kaskel and A. Spitzer
Laboratory and Research Services, Veterans Administration Medical Center, Kansas City, Missouri 64128.
Unlike the case in rat, rabbit, and other species in which nephron
formation continues into the newborn period, nephrogenesis in the guinea
pig is completed well before the time of birth. Therefore, the marked
increase in proximal tubule reabsorption that occurs during the postnatal
period in that species can be attributed entirely to an increase in the
absorptive capacity of existing nephron units. The purpose of the present
morphometric studies was to correlate that change in proximal tubule
function with changes in the apical and basolateral cell membrane surface
areas. The apical and basolateral membrane surface densities were found to
be approximately equal to each other and to remain constant throughout
development. Because of increasing tubule volume, however, both membranes
doubled in size between 1 and 3 wk of age and eventually increased by a
factor of 3.5 in the adult. At the same time, there was little change in
the length of tight function complexes measured in the plane of the luminal
surface. Using previously published functional data and tubule length data,
a good correlation was found between absolute absorption and total
basolateral membrane surface area throughout the entire period of
development in proximal tubules. Absorption per unit area of basolateral
membrane was approximately 0.55, 0.41, 0.56, and 0.42 X 10(-6)
nl.min-1.micron-2 in the 1st, 2nd, and 3rd wk, and in adult animals,
respectively, and thus was similar to that reported for proximal tubule
segments of adult rabbit and juvenile to adult rat.
