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lüll Two-step stimulation of intestinal Ca(2+) absorption during lactation by long-term prolactin exposure and suckling-induced prolactin surge Charoenphandhu N; Nakkrasae LI; Kraidith K; Teerapornpuntakit J; Thongchote K; Thongon N; Krishnamra NAm J Physiol Endocrinol Metab 2009[Sep]; 297 (3): E609-19During pregnancy and lactation, the enhanced intestinal Ca(2+) absorption serves to provide Ca(2+) for fetal development and lactogenesis; however, the responsible hormone and its mechanisms remain elusive. We elucidated herein that prolactin (PRL) markedly stimulated the transcellular and paracellular Ca(2+) transport in the duodenum of pregnant and lactating rats as well as in Caco-2 monolayer in a two-step manner. Specifically, a long-term exposure to PRL in pregnancy and lactation induced an adaptation in duodenal cells at genomic levels by upregulating the expression of genes related to transcellular transport, e.g., TRPV5/6 and calbindin-D(9k), and the paracellular transport, e.g., claudin-3, thereby raising Ca(2+) absorption rate to a new "baseline" (Step 1). During suckling, PRL surge further increased Ca(2+) absorption to a higher level (Step 2) in a nongenomic manner to match Ca(2+) loss in milk. PRL-enhanced apical Ca(2+) uptake was responsible for the increased transcellular transport, whereas PRL-enhanced paracellular transport required claudin-15, which regulated epithelial cation selectivity and paracellular Ca(2+) movement. Such nongenomic PRL actions were mediated by phosphoinositide 3-kinase, protein kinase C, and RhoA-associated coiled-coil-forming kinase pathways. In conclusion, two-step stimulation of intestinal Ca(2+) absorption resulted from long-term PRL exposure, which upregulated Ca(2+) transporter genes to elevate the transport baseline, and the suckling-induced transient PRL surge, which further increased Ca(2+) transport to the maximal capacity. The present findings also suggested that Ca(2+) supplementation at 15-30 min prior to breastfeeding may best benefit the lactating mother, since more Ca(2+) could be absorbed as a result of the suckling-induced PRL surge.|Animals[MESH]|Animals, Suckling[MESH]|Caco-2 Cells[MESH]|Calcium/*metabolism[MESH]|Duodenum/drug effects/metabolism[MESH]|Electric Stimulation[MESH]|Female[MESH]|Humans[MESH]|Intestinal Absorption/*drug effects/physiology[MESH]|Intestinal Mucosa/drug effects/metabolism/physiology[MESH]|Lactation/drug effects/*physiology[MESH]|Pregnancy[MESH]|Prolactin/metabolism/*pharmacology[MESH]|Rats[MESH]|Rats, Sprague-Dawley[MESH]|Sucking Behavior/drug effects/*physiology[MESH]|Time Factors[MESH] |