AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 6 1478-R1483, Copyright © 1991 by American Physiological Society
Compartmental analysis and glomerular filtration in chick embryos
M. J. Murphy, S. C. Brown, N. B. Clark and J. Q. Feng
Department of Biology, State University of New York (SUNY), Agricultural and Technical College, Cobleskill 12043.
We have developed microtechniques that allow the determination of
compartmental fluid distribution and glomerular filtration rate in chick
embryos during three significant developmental periods: phase 1, the
developmental period when the mesonephros alone is functioning; phase 2,
periods of simultaneous meso/metanephric kidney function; and phase 3, the
period during late development when the metanephros completely replaces the
degenerated mesonephros. Water content of tissues is greater in younger
embryos (89.4 +/- 0.2%, day 10) compared with older animals (78.3 +/- 0.5%,
day 18). Although all major tissue components show an absolute increase in
mass during this period, the embryo proper increases at five times the rate
of the extraembryonic tissues. Glomerular filtration rate increases during
development from 0.61 +/- 0.08 ml/h at day 10 to 2.31 +/- 0.11 ml/h at day
18. Glomerular filtration rate scales to body mass with an allometric
exponent identical to adult birds only if total tissue mass (embryo +
membranes) is considered. Our data suggest that significant errors in
allometry will be encountered when scaling measurements are made on
embryonic or fetal amniotes without taking into consideration the
extraembryonic tissues.
