Hypogonadism does not mediate urinary calcium loss in pituitary-grafted rats

Adler, Robert A.; Farrell, Mary E.; Krieg, Richard J.; Deiss, William P.

doi:10.1016/0026-0495(89)90071-1

Cited by 10 publications

(5 citation statements)

References 15 publications

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“…Anterior Pituitary Transplantation. The surgical procedure was modified from the methods of Adler et al (20) and Piyabhan et al (18). During diethyl ether anesthesia, the recipient rat was laid prone on the operating board.…”

Section: Surgery Anterior Pituitary (Ap) Transplantation Wasmentioning

confidence: 99%

“…Because several of the actions of prolactin on calcium metabolism, including stimulation of intestinal calcium transport (17), reduction in urinary calcium secretion (18), and enhancement of bone calcium deposition (18,19), are age-dependent, it would also be interesting to investigate the effect of prolactin in different age groups. To study a long-term effect of high physiological level of prolactin, we used an anterior pituitary transplant technique to induce sustained hyperprolactinemia (18,(20)(21)(22). After transplantation of pituitary glands under the renal capsule, pituitary tissues lacking hypothalamic peptides would stop producing hormones except for prolactin, which is normally under dopaminergic inhibitory regulation (23).…”

Section: Introductionmentioning

confidence: 99%

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Long-Term Prolactin Exposure Differentially Stimulated the Transcellular and Solvent Drag-Induced Calcium Transport in the Duodenum of Ovariectomized Rats

Tudpor

Charoenphandhu

Saengamnart

et al. 2005

Exp Biol Med (Maywood)

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Prolactin, having been shown to stimulate transcellular active and solvent drag-induced calcium transport in the duodenum of female rats, was postulated to improve duodenal calcium transport in estrogen-deficient rats. The aim of the present study was, therefore, to demonstrate the effects of long-term prolactin exposure produced by anterior pituitary (AP) transplantation on the duodenal calcium transport in young (9-week-old) and adult (22-week-old) ovariectomized rats. We found that ovariectomy did not alter the transcellular active duodenal calcium transport in young and adult rats fed normal calcium diet (1.0% w/w Ca) but decreased the solvent drag-induced duodenal calcium transport from 75.50 +/- 10.12 to 55.75 +/- 4.77 nmol.hr(-1).cm(-2) (P < 0.05) only in adult rats. Long-term prolactin exposure stimulated the transcellular active calcium transport in young and adult AP-grafted ovariectomized rats fed with normal calcium diet by more than 2-fold from 7.56 +/- 0.79 to 16.54 +/- 2.05 (P < 0.001) and 9.78 +/- 0.72 to 15.99 +/- 1.75 (P < 0.001) nmol.hr(-1).cm(-2), respectively. However, only the solvent drag-induced duodenal calcium transport in young rats was enhanced by prolactin from 95.51 +/- 10.64 to 163.20 +/- 18.03 nmol.hr(-1).cm(-2) (P < 0.001) whereas that in adult rats still showed a decreased flux from 75.50 +/- 10.12 to 47.77 +/- 5.42 nmol.hr(-1).cm(-2) (P < 0.05). Because oral calcium supplement has been widely used to improve calcium balance in estrogen-deficient animals, the effect of a high-calcium diet (2.0% w/w Ca) was also investigated. The results showed that stimulatory action of long-term prolactin on the transcellular active duodenal calcium transport in both young and adult rats was diminished after being fed a high-calcium diet. The same diet also abolished prolactin-enhanced solvent drag-induced duodenal calcium transport in young and further decreased that in adult AP-grafted ovariectomized rats. We concluded that the solvent drag-induced duodenal calcium transport in adult rats was decreased after ovariectomy. Long-term prolactin exposure stimulated the transcellular active duodenal calcium transport in both young and adult rats whereas enhancing the solvent drag-induced duodenal calcium transport only in young rats. Effects of prolactin were abolished by a high-calcium diet.

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Section: Surgery Anterior Pituitary (Ap) Transplantation Wasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Long-Term Prolactin Exposure Differentially Stimulated the Transcellular and Solvent Drag-Induced Calcium Transport in the Duodenum of Ovariectomized Rats

Tudpor

Charoenphandhu

Saengamnart

et al. 2005

Exp Biol Med (Maywood)

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“…The procedure was modified from the methods of Adler et al [15] and Charoenphandhu et al [14]. After diethylether anesthesia, a 1.0 cm paracostal incision was made to expose the left renal capsule of the recipient rat.…”

Section: Animalsmentioning

confidence: 99%

“…In the present study, the anterior pituitary (AP) transplantation technique was used to induce the sustained high physiological PRL levels of 90-100 ng/ml [15][16][17], which were comparable to the levels during pregnancy in humans and rats [1]. Within 15 days after two extra AP glands were transplanted from donors under the renal capsule of a recipient (i.e., distant from the hypothalamus), a continuous secretion of PRL from the AP allografts in the absence of the hypothalamic dopaminergic inhibition resulted in a sustained physiological hyperprolactinemia [16,18].…”

mentioning

confidence: 99%

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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“…The procedure was modified from the methods of Adler et al (1) and Tudpor et al (45). During diethylether anesthesia, a 1.0-cm paracostal incision was made to expose the left kidney, which was then covered with a warm sterile 0.9% NaCl-soaked gauze ready for transplantation.…”

Section: Ap Transplantationmentioning

confidence: 99%

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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Hypogonadism does not mediate urinary calcium loss in pituitary-grafted rats

Cited by 10 publications

References 15 publications

Long-Term Prolactin Exposure Differentially Stimulated the Transcellular and Solvent Drag-Induced Calcium Transport in the Duodenum of Ovariectomized Rats

Long-Term Prolactin Exposure Differentially Stimulated the Transcellular and Solvent Drag-Induced Calcium Transport in the Duodenum 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

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

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