Nephrology Dialysis Transplantation, Vol 13, Issue 90003 19-22, Copyright © 1998 by Oxford University Press
A Canalejo, A HernAndez, Y Almaden, M Concepcion, A Felsenfeld, A Torres and M Rodriguez
High extracellular phosphorus directly increases parathyroid hormone (PTH)
secretion and gene transcription. The present study evaluates the effect of
high phosphorus diet on the parathyroid cell cycle in rats with normal
renal function. Rats were divided into two groups, receiving either a high
phosphorus diet (HPD, P=1.2%) or a normal phosphorus
diet (NPD, P=0.6%). The dietary calcium content was
0.6% in both diets. Rats were pair fed and sacrificed on days 0, 1, 5, 10
and 15 after initiation of the diet. The parathyroid glands were removed
and parathyroid cells dispersed for evaluation of cell cycle and apoptosis
by flow cytometry. Serum calcium, phosphorus, PTH and calcitriol were
measured. As compared with NPD, the ingestion of a HPD resulted in an
increased number of cells in the S phase of the cell cycle from day 1 to 10
(1.2±0.09% vs 0.6±0.04% for day
1, 1.2±0.11% vs 0.6±0.06% for
day 5 and 1.0±0.09% vs 0.5±0.04%
for day 10, P<0.01). By day 15, the percentage
of cells in the S phase in NPD and HPD were not different. In the rats fed
the HPD, serum PTH increased significantly from day 5 through 15
9P<0.01). Parathyroid cell apoptosis was
minimal and unaffected by the diet. At day 15, the parathyroid gland size
in HPD was increased by 27% as compared with NPD
(P<0.05). This increase should be attributed to
cell proliferation since parathyroid cell size remained unchanged. Serum
calcitriol and calcium were not significantly different in the two groups.
In HPD, and increase in serum phosphorus was observed only on day 1. The
results show that an HPD results in the stimulation of the parathyroid cell
cycle independently of changes in calcium and
calcitriol.Keywords: apoptosis; calcium; cell cycle;
parathyroid hormone; parathyroid hyperplasia; phosphorus
ORIGINAL ARTICLES
The effect of a high phosphorus diet on the parathyroid cell cycle
Unidad de Investigacion, Servicio de Nefrologia Hospital Universitario Reina Sofia, c/ Avda Menendez Pidal s/n, E-14004 Cordoba, Spain; Unidad de Investigacion, Servico de Nefrologia Hospital Universitario de Tenerife, Canarias, Spain; Department of Medicine, West Los Angeles VA Medical Center and UCLA, Los Angeles, CA, USA; Corresponding author
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