Long-term prolactin exposure differentially stimulated the transcellular and solvent drag-induced calcium transport in the duodenum of ovariectomized rats.
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.
Tudpor
Kukiat
K
Department of Physiology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
Charoenphandhu
Narattaphol
N
Saengamnart
Wasana
W
Krishnamra
Nateetip
N
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002136:Calcium, Dietary / Q000008:administration & dosage*; D004386:Duodenum / Q000378:metabolism*; D005260:Female; D017136:Ion Transport / Q000187:drug effects; D009924:Organ Culture Techniques; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000378:metabolism* / Q000637:transplantation; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012997:Solvents / Q000494:pharmacology; D013997:Time Factors
D002136:Calcium, Dietary; D012997:Solvents; D011388:Prolactin; D002118:Calcium