Involvement of cholecalciferol metabolism in birds in the adaptation of calcium absorption to the needs during reproduction

Bär, A.; Cohen, A H; Edelstein, S.; Shemesh, Mordechai; Montecuccoli, Guilia; Hurwitz, S.

doi:10.1016/0305-0491(78)90254-7

Cited by 22 publications

(8 citation statements)

References 22 publications

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“…Therefore, it may be concluded that plasma Ca levels of laying hens is a strong regulator of this enzymatic system. This conclusion is in agreement with previous reports (Bar et al, 1978;Forte et al, 1983;Armbrecht and Forte, 1985;Martz et al, 1985;Elaroussi et al, 1993).…”

Section: Discussionsupporting

confidence: 95%

“…The main hormones controlling this balance are parathyroid hormone (PTH), calcitonin, and 1,25-dihydroxycholecalciferol [l,25(OH) 2 D 3 ] produced by the renal conversion of 25-hydroxycholecalciferol [25(OH)D 3 ] through the activity of the enzyme 25-hydroxycholecalciferol-1-hydroxylase (la-hydroxylase). In laying birds, increased Ca demands during the laying cycle are accommodated by an appropriate increase in intestinal Ca absorption (Bar et al, 1978) and a decrease in renal Ca excretion (DeLuca et al, 1990). Both renal la-hydroxylase activity and plasma l,25(OH) 2 D 3 concentrations are significantly higher during the active stage of eggshell calcification than in other stages (Abe et al, 1979).…”

Section: Introductionmentioning

confidence: 98%

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Calcium Homeostasis in the Laying Hen.

et al. 1994

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An experiment was carried out to investigate the effects of age of laying hens (young = 22 wk vs old = 120 wk) in maintaining Ca homeostasis during periods of Ca depletion then repletion with Ca. Plasma Ca and P, tibia breaking strength and percentage ash, renal 25-hydroxycholecalciferol-1-hydroxylase (1 alpha-hydroxylase), and parathyroid hormone (PTH)-stimulated adenylate cyclase activities were studied during 28 d of Ca depletion on a .08% Ca diet (LC) and 28 d of Ca repletion on a 3.75% Ca diet (HC). When laying hens on a HC diet were placed on a LC diet, plasma Ca and P, tibia breaking strength and ash percentage, and renal PTH-dependent adenylate cyclase activity were significantly depressed, but renal 1 alpha-hydroxylase activity was significantly stimulated. These changes were greater in the young hens than in the older hens; therefore an interaction between age and dietary Ca was found. These changes were of a lesser magnitude at 28 d of Ca depletion, probably due to the cessation of egg laying and to the desensitization of hormone-mediated function. 1 alpha-Hydroxylase activity was significantly less during the repletion period. The age effect was most pronounced for 1 alpha-hydroxylase, with the younger birds expressing significantly higher activity and ability to respond to hypocalcemia. There was a significant increase in kidney weights in Ca-deficient groups at 14 and 28 d of Ca depletion. It is concluded that younger hens have greater adaptive responses to Ca restriction than do older hens.

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Section: Discussionsupporting

confidence: 95%

Section: Introductionmentioning

confidence: 98%

Calcium Homeostasis in the Laying Hen.

et al. 1994

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“…Activity of 25-hydroxycholecalciferol-l-hydroxylase [25(OH)D 3 ]-l-hydroxylase of kidney is markedly increased in laying hens (Kenny, 1976;Castillo et al, 1977;Martz et al, 1985), which appears to be responsible for increased concentration of circulating 1,25-dihydroxycholecalciferol [l,25(OH) 2 D 3 ] (Castillo et al, 1979;Martz et al, 1985). This sterol hormone is thought to mediate the increased intestinal absorption of calcium and phosphorus that has been described in laying birds (Bar et al, 1978). Estrogen treatment of juvenile birds of either sex leads to an increase in renal [25-(OH)D 3 ]-l-hydroxylase activity and plasma l,25(OH) 2 D 3 levels similar to that observed in laying birds (Tanaka et al, 1976;Baksi and Kenny, 1977a;Pike et al, 1978;Martz et al, 1985;Sommerville et al, 1989).…”

Section: Introductionmentioning

confidence: 90%

“…The arrest of egg production by NCZ prevents the final stages of follicle maturation without total suppression of the ovary. Thus, estrogen and estrogen-dependent characteristics such as high plasma calcium and the presence of medullary bone are maintained under these conditions (Bar et al, 1978).…”

Section: Protocols For Physiological and Pharmacological Approachesmentioning

confidence: 99%

Adaptation of the Kidney During Reproduction: Role of Estrogen in the Regulation of Responsiveness to Parathyroid Hormone

et al. 1993

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Avian kidney function adapts during reproduction to provide the calcium required for eggshell formation. Adaptive changes in kidney function are 1) increased parathyroid hormone (PTH)-dependent adenylate cyclase activity; 2) elevated numbers of PTH receptors; and 3) increased synthesis of 1,25-dihydroxycholecalciferol. Because exogenous estrogen mimics these changes, this study explored the physiological role of estrogen in the regulation of kidney function by altering egg-laying status or levels of estradiol. In hens, treatment with the coccidiostatic drug, nicarbazin, led to cessation of egg laying with maintenance of the reproductive tract and of plasma estradiol and calcium. The PTH-dependent adenylate cyclase activity remained elevated (upregulated). However, when molting was induced by altering the photoperiod and diet, plasma estradiol, plasma calcium, and renal PTH-dependent adenylate cyclase activity all decreased. The depressed responsiveness to PTH was restored by administration of estradiol either during the molt or upon return to egg laying following the molt. When the estrogen antagonist, tamoxifen, was administered to laying hens, reproduction ceased and the PTH-dependent adenylate cyclase activity of renal membranes was decreased. In all three groups of nonlaying birds, the activity of kidney 25-hydroxycholecalciferol-1-hydroxylase was markedly decreased relative to that of laying hens irrespective of the amount of plasma estradiol. It was concluded that estrogen regulates the PTH-dependent adenylate cyclase system of avian kidney, whereas the activity of the 25-hydroxycholecalciferol-1-hydroxylase of kidney and thus, the synthesis of 1,25-hydroxycholecalciferol may be governed at least in part by the regulation of renal receptors for PTH by estrogen.

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“…The steroid hormone 1,25-dihydroxyvitamin D, [1,25(OH),D,] has long been known to regulate calcium metabolism in obvious target tissues including bone, kidney and the intestine. Other work carried out recently shows this hormone to be responsible for the upregulation or inhibition of a large number of genes affecting Correspondmce to: M.W.…”

Section: Introductionmentioning

confidence: 99%