The effect of oophorectomy on calcium homeotasis

Morris, H. A.; O’Loughlin, Peter; Mason, Richard; Schulz, SR

doi:10.1016/8756-3282(95)00289-p

Cited by 6 publications

(6 citation statements)

References 17 publications

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“…Calcium balance was reduced by oophorectomy as would be expected from previous studies in rats [7,9,12] and humans [1,3,[13][14][15][16]. The increase in calcium loss from the bowel in the OOX animals compared with the shamoperated animals was significantly greater.…”

Section: Discussionsupporting

confidence: 58%

“…The standard rat diet of 1% is achieved by supplementation with calcium carbonate and cannot be considered a natural rat diet. Previous studies have shown that OOX rats on a high calcium diet are in positive calcium balance [7,10] whereas postmenopausal women are in negative calcium balance [1,5]. Postmenopausal women have an average intake of 800 mg or approximately 0.05% of the dry weight of the diet [11].…”

Section: Discussionmentioning

confidence: 98%

“…Recently, it has been suggested that the major component of calcium balance to be affected with estrogen deficiency in growing rats is intestinal calcium secretion [7].…”

mentioning

confidence: 99%

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The Effect of Estrogen Deficiency on Calcium Balance in Mature Rats

Draper

Dick

Prince

1999

Calcified Tissue International

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The role of estrogen in the regulation of calcium balance is still poorly understood. A calcium balance study was performed to examine the effects of estrogen status in relation to fecal calcium loss as a component of bone loss after oophorectomy (OOX) in the mature rat. The components of the classic calcium balance were compared with calcium balance estimates obtained from whole body bone density. Six month or older Sprague Dawley rats were allocated to either a sham-operated or OOX group and fed a 0.1% calcium diet. The bone mineral density (BMD) and bone mineral content (BMC) were measured at baseline, 6 weeks, and 9 weeks. A calcium balance was done for 6 days before and 6 weeks post OOX. The fall in BMD from baseline to 9 weeks in the OOX group was significantly greater than in the sham-operated group. The calcium balance was more negative at baseline than at 6 weeks in both groups of animals because they had not adapted to the low calcium diet. However, the increase in calcium balance was significantly less in the OOX animals than in the sham-operated animals. The greater the rise in calcium balance from the baseline to the 6 weeks balance the less the fall in the calcium content of the whole body (Spearman correlation: r = 0.604 P = 0.008). The fall in fecal calcium, but not urine calcium or calcium consumed, was negatively correlated with the change in whole body BMC (Spearman correlation: fecal calcium r = -0.763 P = 0.001). Thus, the primary effect of estrogen deficiency on calcium balance in the mature rat appears to be calcium flux in the bowel, rather than renal calcium handling.

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Section: Discussionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 98%

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The Effect of Estrogen Deficiency on Calcium Balance in Mature Rats

Draper

Dick

Prince

1999

Calcified Tissue International

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“…These data indicate that urine calcium excretion by ovariectomized rats was high relative to the amount of calcium absorbed from the diet. A small but significant rise in the fasting urine calcium excretion following ovariectomy in the rat has recently been reported (Morris et al 1995). There was no effect of ovariectomy on intestinal calcium secretion in adult rats.…”

Section: Discussionmentioning

confidence: 99%

“…Ovariectomy in the rat leads to a reduction in bone density at a number of skeletal sites (Wronski et al 1988; Kalu et al 1989; Yamazaki & Yamaguchi, 1989) and in the young rat causes an increase in intestinal calcium secretion, leading to impaired calcium balance (O'Loughlin & Morris, 1994). The effect of ovariectomy on urine calcium excretion is currently controversial with no effect (Morris et al 1992; O'Loughlin & Morris, 1994), an inconsistent effect (Yamazaki & Yamaguchi, 1989) and an increase in urine calcium excretion (Morris et al 1995) having been reported. Net intestinal calcium absorption in rats fed a low calcium diet is impaired by ovariectomy (Kalu et al 1989); however, whether this impairment is the result of a reduction in true calcium absorption or increased intestinal calcium secretion is unclear.…”

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confidence: 99%

Oestrogen deficiency impairs intestinal calcium absorption in the rat

O’Loughlin

Morris

1998

The Journal of Physiology

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The effects of ovariectomy on the relationships between calcium consumption and calcium balance and its components were assessed in adult (10‐14 months) sham‐operated and ovariectomized (Ovx) rats fed a semi‐synthetic diet with the calcium content varying between 0·02 and 0·4 %. Adaptation to dietary calcium restriction was monitored for 47 days from commencement of a 0·02 % Ca diet. Response to 1,25‐dihydroxyvitamin D (20 ng kg−1 day−1) administration in sham and Ovx rats and oestradiol (E2) (20 μg kg−1 day−1) replacement in Ovx rats was assessed in rats fed a 0·05 % Ca diet. Ovx rats had lower intercepts for the relationships between calcium consumption and both calcium balance (P < 0·005) and intestinal calcium absorption (P < 0·005) compared with sham rats, but 1,25‐dihydroxyvitamin D was not reduced in Ovx rats. The magnitude of adaptation to dietary calcium restriction was unaffected by ovariectomy. Intestinal calcium absorption was stimulated by an equivalent amount in sham and Ovx rats following 1,25‐dihydroxyvitamin D administration, although this did not reach statistical significance for sham (sham, t= 1·91, n.s.; Ovx, t= 3·18, P < 0·05). Oestradiol replacement in Ovx rats induced a marked increase in intestinal calcium absorption (t= 8·25, P < 0·005), without stimulating circulating 1,25‐dihydroxyvitamin D levels and led to a marked increase in calcium balance (t= 6·89, P < 0·005). These data indicate that the impairment of intestinal calcium absorption following ovariectomy is not the result of reduced circulating 1,25‐dihydroxyvitamin D or reduced intestinal responsiveness to 1,25‐dihydroxyvitamin D. Moreover E2 stimulates intestinal calcium absorption probably by a direct effect on the intestine.

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Ionized Calcium and Bone Turnover in the Estrogen-Deficient Rat

Schulz

Morris

1999

Calcif Tissue Int

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The long-term effects of high bone resorption on blood ionized calcium and calciotropic hormone levels following oophorectomy in 6-month-old Sprague-Dawley female rats were investigated. Fasting urine and blood samples were collected from 16 sham and 16 oophorectomized (oophx) rats preoperatively and up to 130 days postoperatively. From 50 days postoperation, daily injections of 17-beta estradiol (E2) (20 microg/kg body weight) were administered subcutaneously to eight of the oophx rats. Urine hydroxyproline excretion (OHPrE) and serum osteocalcin were significantly elevated (P < 0.001) as a result of oophorectomy and normalized within 6 days of E2 replacement. Urine deoxypyridinoline and total serum alkaline phosphatase were significantly elevated (P < 0.001) following oophorectomy and suppressed to control levels after 37 days of E2 replacement. Blood ionized calcium was significantly reduced in oophx rats (P < 0.001) compared with sham rats and was normalized by E2 replacement at 55 days posttreatment. Serum 1,25 dihydroxyvitamin D (1,25(OHD)2D3) was significantly elevated (P < 0.001) in oophx rats and again was normalized by E2 at 55 days posttreatment. Serum parathyroid hormone (PTH) was unaffected by oophorectomy. These data indicate that despite increased bone resorption following oophorectomy, blood ionized calcium levels are decreased. The increased bone turnover in oophx rats was rapidly suppressed by E2 replacement before ionized calcium levels were normalized, suggesting a direct effect of estrogen on the modulation of bone cell activity. The depression of blood ionized calcium levels following oophorectomy, which is not mediated by calciotropic hormones, suggests an effect of estrogen on intestinal calcium absorption, renal handling of calcium, or a combination of both.

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The effect of oophorectomy on calcium homeotasis

Cited by 6 publications

References 17 publications

The Effect of Estrogen Deficiency on Calcium Balance in Mature Rats

The Effect of Estrogen Deficiency on Calcium Balance in Mature Rats

Oestrogen deficiency impairs intestinal calcium absorption in the rat

Ionized Calcium and Bone Turnover in the Estrogen-Deficient Rat

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