Acute Effect of Prolactin on Bone 45Ca Accumulation in Rats.

Krishnamra, Nateetip; Seemoung, J; Limlomwongse, Liangchai

doi:10.1507/endocrj.44.257

Cited by 13 publications

(8 citation statements)

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“…Puntheeranurak et al (40) in 2006 showed that, after Ovx, prolactin-enhanced bone calcium deposition in trabecular bones of adult rats was diminished, but cortical bones were not studied. Because the 45 Ca kinetic technique was a highly sensitive method that could detect the vertebral and sternal calcium turnover within 60 min after prolactin administration (28,29), the present findings (Fig. 5), therefore, reliably indicated a persistent lack of prolactin action on tibia and femur after Ovx.…”

Section: Discussionsupporting

confidence: 56%

“…On the other hand, a 1-mo period was sufficient to show the effects of prolactin alone or prolactin plus estrogen depletion on bone calcium deposition (28,39,40). Indeed, using short-term 45 Ca kinetic technique, prolactin actions on bone calcium metabolism were seen in Ͻ2 h, suggesting that it affected the rapidly exchangeable calcium pool (29).…”

Section: Discussionmentioning

confidence: 99%

“…Other pituitary hormones were not secreted due to the absence of the respective stimulatory hypothalamic hormones. In the 45 Ca kinetic study, which was a sensitive method to detect 45 Ca deposit in bone and exchangeable bone calcium pool (19,29), high plasma prolactin levels were obtained by subcutaneous injection, because an abrupt increase in prolactin level was required at the start of the experiment (day 14 in Fig. 1).…”

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confidence: 99%

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High-calcium diet modulates effects of long-term prolactin exposure on the cortical bone calcium content in ovariectomized rats

Charoenphandhu

Tudpor²,

Thongchote³

et al. 2007

American Journal of Physiology-Endocrinology and Metabolism

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High physiological prolactin induced positive calcium balance by stimulating intestinal calcium absorption, reducing renal calcium excretion, and increasing bone calcium deposition in female rats. Although prolactin-induced increase in trabecular bone calcium deposition was absent after ovariectomy, its effects on cortical bones were still controversial. The present investigation, therefore, aimed to study the effect of in vivo long-term high physiological prolactin induced by either anterior pituitary (AP) transplantation or 2.5 mg/kg prolactin injection on cortical bones in ovariectomized rats. Since the presence of prolactin receptors (PRLR) in different bones of normal adult rats has not been reported, we first determined mRNA expression of both short- and long-form PRLRs at the cortical sites (tibia and femur) and trabecular sites (calvaria and vertebrae) by using the RT-PCR. Our results showed the mRNA expression of both PRLR isoforms with predominant long form at all sites. However, high prolactin levels induced by AP transplantation in normal rats did not have any effect on the femoral bone mineral density or bone mineral content. By using 45Ca kinetic study, 2.5 mg/kg prolactin did not alter bone formation, bone resorption, calcium deposition, and total calcium content in tibia and femur of adult ovariectomized rats. AP transplantation also had no effect on the cortical total calcium content in adult ovariectomized rats. Because previous work showed that the effects of prolactin were age dependent and could be modulated by high-calcium diet, interactions between prolactin and these two parameters were investigated. The results demonstrated that 2.0% wt/wt high-calcium diet significantly increased the tibial total calcium content in 9-wk-old young AP-grafted ovariectomized rats but decreased the tibial total calcium content in 22-wk-old adult rats. As for the vertebrae, the total calcium contents in both young and adult rats were not changed by high-calcium diet. The present results thus indicated that the adult cortical bones were potentially direct targets of prolactin. Moreover, the effects of high physiological prolactin on cortical bones were age dependent and were observed only under the modulation of high-calcium diet condition.

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Section: Discussionsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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High-calcium diet modulates effects of long-term prolactin exposure on the cortical bone calcium content in ovariectomized rats

Charoenphandhu

Tudpor²,

Thongchote³

et al. 2007

American Journal of Physiology-Endocrinology and Metabolism

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“…Over 300 effects of its biological activity have been demonstrated in various animal species (Dróżdż et al, 1998;Nicoll, 1980;Ryszka et al, 2002;Wang et al, 2007;Scotti et al, 2008). The study also demonstrated that it influences calcium management (Krishnamara et al, 1993(Krishnamara et al, , 1997Krishnamara and Taweerathitan, 1995;Tanrattana et al, 2004).…”

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confidence: 95%

The influence of prolactin on bone mineral density (BMD) and some biochemical markers of ovariectomized rats

Dolińska¹,

Suszka-Świtek²,

Drăgan³

et al. 2010

CZECH J ANIM SCI

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ABSTRACT:A model of postmenopausal osteoporosis was used in the study. 107 days after ovariectomy the animals were subcutaneously applied 1.0 IU PRL/kg BM or 1.0 IU calcitonin/kg BM for 7 days in single doses. The application of the preparations started again 80 days after the first application. After 194 days the animals were narcotized, blood was collected, and lumbar (L2-L4) and femoral bones were prepared. The material obtained was subjected to densitometric analysis of bone mineral density (BMD). In ovariectomized rats the loss of osseous tissue was observed only in the lumbar bone. The application of prolactin to ovariectomized rats caused an increase in the mineral density of the lumbar bone up to a BMD value equal to that of the control group which had not been subjected to ovariectomy (control healthy group -SHAM). Similar results were obtained in the case of calcitonin. An increase in osteocalcin concentration and activity of isoenzyme alkaline phosphatase (BAL), with a decrease in the activity of isoenzyme acid phosphatase (TRAP) was observed in experimental groups compared to control ones.

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“…However, the direct effect of PRL on osteoblasts to enhance bone turnover was complicated by its indirect actions through hyperprolactinemiainduced hypogonadism, which in turn induced chronic estrogen deficiency [8,9]. Moreover, the PRL-enhanced calcium absorption may indirectly contribute to the increase in bone calcium deposition, as previously suggested by the 45 Ca kinetic and histomorphometric techniques [10][11][12]. Nevertheless, the effects of PRL on bone were mostly confined to the trabecular sites [13], e.g., sternum, vertebrae, and trochanter, because a 2-week exposure to high physiological PRL altered calcium deposition or the total calcium content in these bones, but not in the tibia and femur of adult rats [6,14].…”

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confidence: 92%

High Physiological Prolactin Induced by Pituitary Transplantation Decreases BMD and BMC in the Femoral Metaphysis, but Not in the Diaphysis of Adult Female Rats

2008

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High physiological prolactin (PRL) stimulated intestinal calcium absorption and renal calcium uptake in mammals. Previous histomorphometric study revealed a significant increase in bone turnover in the trabecular part of the PRL-exposed long (cortical) bone; however, whole-bone densitometric analysis was unable to demonstrate such effect. We therefore studied differential changes in bone mineral density (BMD) and contents (BMC) of the femoral diaphysis and metaphysis in adult female rats exposed to high PRL induced by anterior pituitary (AP) transplantation. The estrogen-dependent effects of PRL on the femur were also investigated. We found that chronic exposure to PRL had no effect on BMD or BMC of the femoral diaphysis, which represented the cortical part of the long bone. It is interesting that 7 weeks after an AP transplantation, BMD and BMC of the femoral metaphysis were significantly decreased by 8% and 14%, respectively. Ovariectomy (Ovx) for 2, 5, and 7 weeks also decreased BMD and BMC in the femoral metaphysis, but not in the diaphysis. However, the AP transplantation plus Ovx (AP+Ovx) produced no additive effects. Nevertheless, 2.5 µg/kg 17β-estradiol (E2) supplementation abolished the osteopenic effects of both Ovx and AP+Ovx on the femur. As for the L5-6 vertebrae, BMD and BMC were not affected by PRL exposure, but were significantly decreased by Ovx and AP+Ovx, and such decreases were completely prevented by E2 supplementation. It could be concluded that high physiological PRL induced a significant osteopenia in the trabecular part, i.e., the metaphysis, of the femora of adult female rats in an estrogen-dependent manner. Since PRL had no detectable effect on the vertebrae, the effects of PRL on bone appeared to be site-specific.Key words: diaphysis, femur, metaphysis, prolactin, vertebrae.Prolactin (PRL), as a calcium-regulating hormone, has been reported to stimulate intestinal calcium absorption, enhance renal calcium reabsorption, and induce high bone turnover in nonmated female rats [1][2][3]. By regulating calcium mobilization in these target organs during pregnancy and lactation, the high physiological PRL of 75-300 ng/ ml increases calcium availability for fetal growth and milk production [4]. Moreover, the basal PRL level of 7-10 ng/ ml was required for the maintenance of normal bone turnover and duodenal calcium absorption in rats [5,6].It has been shown that PRL acted directly on the intestinal absorptive cells to enhance calcium absorption [3]. In bone, osteoblasts but not osteoclasts strongly expressed functional PRL receptors (PRLR), indicating that bone was also a target of PRL [7]. However, the direct effect of PRL on osteoblasts to enhance bone turnover was complicated by its indirect actions through hyperprolactinemiainduced hypogonadism, which in turn induced chronic estrogen deficiency [8,9]. Moreover, the PRL-enhanced calcium absorption may indirectly contribute to the increase in bone calcium deposition, as previously suggested by the 45 Ca kinetic and histomorphometri...

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Acute Effect of Prolactin on Bone 45Ca Accumulation in Rats.

Cited by 13 publications

References 49 publications

High-calcium diet modulates effects of long-term prolactin exposure on the cortical bone calcium content in ovariectomized rats

High-calcium diet modulates effects of long-term prolactin exposure on the cortical bone calcium content in ovariectomized rats

The influence of prolactin on bone mineral density (BMD) and some biochemical markers of ovariectomized rats

High Physiological Prolactin Induced by Pituitary Transplantation Decreases BMD and BMC in the Femoral Metaphysis, but Not in the Diaphysis of Adult Female Rats

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