Influence of Ovariectomy and Estradiol Treatment on Calcium Homeostasis During Aging in Rats

Abstract

Study was carried out an Wistar female rats to evaluate the consequences of ovariectomy and 17 beta-estradiol substitutive treatment during aging on bone. Ca metabolism and calciotropic hormones. Three groups of fifteen rats, mature, old and senescent (4-, 10-, and 28 month-old) female were fed a diet (6 g/100 g BW/day) containing 0.9% Ca and 0.8% Pi, Within each group, 10 rats were surgically ovariectomized (OVX). From day 1 until day 60 after OVX, they were subcutaneously injected with either 17 beta-estradiol (E: 10 micrograms/kg BW/48 h; n = 5) or with solvent alone (OVX; n = 5). Five other rats were sham operated (SH) and received solvent alone. Animals were put in balance 1 day per week to determine Ca and Pi intestinal apparent absorption and urinary pyridinium cross-links excretion was measured by HPLC. All rats were killed by exsanguination 60 days after OVX. Plasma was collected for measurement of intact parathyroid hormone (PTH), calcitonin (CT), insulin-like growth factor-1 (IGF-1), Ca and Pi. The success of OVX was confirmed at necropsy by observation of marked atrophy of the uterine horns. The right femur was collected, cleaned from adjacent tissue and used for mineral analysis. Despite correct matching for feeding, BW was significantly larger in 6 and 12 month-old OVX rats. OVX and 17 beta-estradiol had no significant effect upon plasma Ca, Pi and CT concentrations. Aging is associated with increased circulating PTH levels (pg/ml) (SH-6 months: 50.8 +/- 12.6; 12 months: 219.1 +/- 34.9; 30 months: 158.7 +/- 23.5; P < 0.05). Urinary and fecal Ca and Pi excretion in senescent animals were higher than in adult or old rats, thus resulting in a drastic fall in both intestinal apparent absorption and retention of Ca and Pi in 30 month-old animals. In each group, urinary pyridinium cross-links excretion and plasma osteocalcin concentration were higher in the OVX animals than in the controls, consistent with increased bone turnover in the estrogen deficient state. Both biochemical turnover markers were reduced in the estrogen-treated groups. In the same way, OVX increased and estrogen decreased the plasma IGF-1 levels. We conclude that 17 beta-estradiol prevents high turnover-induced osteopenia even in 30 month-old rats.

Effect of oligofructose or dietary calcium on repeated calcium and phosphorus balances, bone mineralization and trabecular structure in ovariectomized rats

“…Ca retention was not significantly lower following ovariectomy, indicating a lack of sensitivity of the metabolic balance to the small effects of oestrogen deficiency in adult rats. Reports on the effect of ovariectomy on Ca absorption are equivocal (Thomas et al 1988;O'Loughlin & Morris, 1994;Gaumet et al 1997), depending on the study design. In general, a significant loss of cancellous bone area is associated with a loss of Tb.N in ovariectomized rats (Kimmel, 1996;Kapadia et al 1998).…”

“…4). The better responsiveness of young, compared with aged rats may be explained by decreased intestinal and renal functions, known to be associated with ageing in the rat (Armbrecht et al 1980;Gaumet et al 1997), and by additional effects on mineral retention by increases in bone mass during growth. Urinary Ca increased with increasing dose of oligofructose, due to the higher apparent Ca absorption and not to increased bone resorption, as indicated by Ca balance (Table 3), femur Ca content (Fig.…”

Effects of Vitamin K2 (Menatetrenone) on Calcium Balance in Ovariectomized Rats

“…However, the results thereof are not always in agreement with those seen clinically (20,21). In this study, therefore, we investigated the effects of OVX on the Ca balance and whether vitamin K2 improves these changes in rats.…”

Treatment of Radix Dipsaci extract prevents long bone loss induced by modeled microgravity in hindlimb unloading rats

“…Furthermore, treatment with RDE not only led to a decrease in serum and urinary bone resorption markers (TRAP, NTx, CTx, and DPD) but also resulted in an increase in serum bone formation markers (BALP and OC). In addition, an increase in urinary Ca and P as well as a decrease in Ca and P absorption efficiency might contribute to the reduction of BMD (Gaumet et al, 1997). RDE could prevent the HLU-induced increase in urinary Ca and P. These effects of RDE and ALN treatment were consistent with the maintenance of bone mass by inhibiting bone remodeling in both groups.…”