Effects of N,N,N′,N′-ethylenediaminetetramethylene phosphonic acid and 1-hydroxyethylidene-1,1-bisphosphonic acid on calcium absorption, plasma calcium, longitudinal bone growth, and bone histology in the growing rat

Absorptive and secretory capacities of six in situ intestinal loops of equal length were compared under the same calcium load and calcemic condition. The highest rate of calcium absorption was found in duodenum, colon, and proximal jejunum when loops were filled with 0.3 mM calcium, and in duodenum and proximal jejunum when filled with 10 mM luminal calcium. Secretory rates were in the following order: duodenum, jejunum, proximal jejunum, cecum, ileum, and proximal colon. Absorption of 0.3 mM calcium was decreased in all but the cecum and colon during hypercalcemia, and in duodenum, proximal jejunum, and colon during thyroparathyroidectomy-induced hypocalcemia. In contrast, calcium secretion was directly related to plasma calcium concentration and the length of the intestine. Functional resection of any part met with a compensatory increase in calcium absorption by the remaining segments, with the exception of the resection of the distal ileum with the large bowel. In conclusion, proximal small intestine exhibited the highest rate of absorption and secretion, but functional resection of this or any part did not affect the overall calcium absorption if luminal calcium was 10 mM. Moreover, enhanced secretion and reduced absorption during hypercalcemia were beneficial with respect to plasma calcium regulation.Key words: calcium, hypercalcemia, hypocalcemia, intestinal absorption, intestinal secretion.

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Longitudinal bone growth after sciatic denervation in rats

Journal of Bone and Joint Surgery - British Volume ◽

10.1302/0301-620x.70b2.3346314 ◽

1988 ◽

Vol 70-B (2) ◽

pp. 315-318 ◽

Cited By ~ 14

Author(s):

GL Garces ◽

ME Santandreu

Keyword(s):

Bone Growth ◽

Longitudinal Bone Growth

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Estrogen receptor specificity in the regulation of the skeleton in female mice

Journal of Endocrinology ◽

10.1677/joe.0.1710229 ◽

2001 ◽

Vol 171 (2) ◽

pp. 229-236 ◽

Cited By ~ 140

Author(s):

MK Lindberg ◽

SL Alatalo ◽

JM Halleen ◽

S Mohan ◽

JA Gustafsson ◽

...

Keyword(s):

Estrogen Receptor ◽

Estrogen Receptor Alpha ◽

Bone Growth ◽

Fat Content ◽

Mineral Density ◽

Trabecular Bone Mineral Density ◽

Longitudinal Bone Growth ◽

Female Mice ◽

Opposing Effects ◽

Er Alpha

There are two known estrogen receptors, estrogen receptor-alpha (ER alpha) and estrogen receptor-beta (ER beta), which may mediate the actions of estrogen. The aim of the present study was to compare fat content, skeletal growth and adult bone metabolism in female mice lacking ER alpha (ERKO), ER beta (BERKO) or both ERs (DERKO). We demonstrate that endogenous estrogens decrease the fat content in female mice via ER alpha and not ER beta. Interestingly, the longitudinal bone growth was decreased in ERKO, increased in BERKO, but was intermediate in DERKO females, demonstrating that ER alpha and ER beta exert opposing effects in the regulation of longitudinal bone growth. The effects on longitudinal bone growth were correlated with similar effects on serum levels of IGF-I. A complex regulation of the trabecular bone mineral density (BMD), probably caused by a disturbed feedback regulation of estrogen and testosterone, was observed in female ER-inactivated mice. Nevertheless, a partial functional redundancy for ER alpha and ER beta in the maintenance of the trabecular BMD was observed in the female mice at 60 days of age. Thus, ER alpha and ER beta may have separate effects (regulation of fat), opposing effects (longitudinal bone growth) or partial redundant effects (trabecular BMD at 60 days of age), depending on which parameter is studied.

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