
studies of the changes in growth
and dna synthesis in the rat kidney
during experimentally induced
renal hypertrophy
there is a high rate of accumulation of
newly synthesized dna in the kidney after folic
acid injection, compared with the small increase
during the first few days after unilateral nephrectomy.
there is a large increase in the water content
of the kidney after folic acid which does not
occur after unilateral nephrectomy.  the changes
in the wet and dry weight and the rna and dna
content of the kidney have been compared after
administration of folic acid, unilateral nephrectomy
and unilateral nephrectomy followed by folic
acid 24 hr later in an attempt to study the nature
of these differences.  after unilateral nephrectomy
there was a steady increase in wet weight, dry
weight and rna content of the kidney, each parameter
reaching about 35 to 40% above normal by
14 days, by which time the dna content had increased
by only about 25%.  an increased rate of
dna synthesis was found between 2 and 4 days,
returning almost to normal by 7 days.  after folic
acid injection there were very large increases in
wet weight (60%), rna content (100%) and dna content
(70%) during the first 4 days accompanied by
a smaller increase in dry weight (30%).  thereafter
these parameters declined, relative to body weight,
returning almost to normal by 14 days.  the rate
of dna synthesis was greatly increased as early
as 24 hr after injection and reached a much higher
level than that found after unilateral nephrectomy,
before returning to the normal level by 7 days.
when unilateral nephrectomy was followed 24 hr
later by folic acid injection, the increases in
weight, nucleic acid content and rate of dna synthesis
were greater than at the corresponding
times after either treatment alone.  marked differences
were found in the labeling indices of kidney
cells after either unilateral nephrectomy or folic
acid injection.  the latter treatment resulted in very
large increases in all three zones of the kidney,
whereas after unilateral nephrectomy the responses
of the cortex and outer medulla were much lower,
with no significant increase in the inner medulla.
when both treatments were combined, the response
of the remaining kidney was similar to, though
more exaggerated than, that of the normal kidney
after folic acid injection.
