Two-step stimulation of intestinal Ca²⁺absorption during lactation by long-term prolactin exposure and suckling-induced prolactin surge

Abstract

Charoenphandhu N, Nakkrasae L, Kraidith K, Teerapornpuntakit J, Thongchote K, Thongon N, Krishnamra N. Two-step stimulation of intestinal Ca 2ϩ absorption during lactation by longterm prolactin exposure and suckling-induced prolactin surge.

Parathyroid hormone (PTH) rapidly enhances CFTR-mediated HCO3− secretion in intestinal epithelium-like Caco-2 monolayer: a novel ion regulatory action of PTH

“…Finally, the responsible signaling pathways were identified by pretreating Caco-2 monolayers on both apical and basolateral sides with inhibitors of known PTH signaling pathways, i.e., cAMP-dependent PKA (10 mol/l myristoylated PKI 14 -22 amide; Calbiochem, San Diego, CA), intracellular Ca 2ϩ [50 mol/l 1,2-bis(2-aminophenoxy)ethane-N,N,N=,N=-tetraacetic acid tetra(acetoxymethyl ester); BAPTA-AM; Calbiochem], Ca 2ϩ -dependent PKC (1 mol/l GF-109203X; A. G. Scientific, San Diego, CA), and phosphoinositide 3-kinase (PI3K; 200 nmol/l wortmannin and 75 mol/l LY-294002; Tocris Bioscience, Bristol, UK). The signaling pathway inhibitors were of the optimal concentrations as reported previously (10,28,31,65).…”

“…The PCR technique was modified from the method of Charoenphandhu et al (10). In brief, total RNA was extracted from Caco-2 cells by TRIzol reagent (Invitrogen, Carlsbad, CA), according to the manufacturer's instruction.…”

“…Impedance spectroscopy was performed by using 1255B frequency response analyzer and 1287A electrochemical interface (Solartron, Farnborough, UK). Sine-wave alternating current (35 A/cm 2 root mean square amplitude, 0.5 Hz-10 kHz) was applied across Caco-2 monolayer at different time points, i.e., before adding 10 nmol/l PTH 1-34 or 10 mol/l forskolin, and at 1,5,10,15,20,25,30,35 (Fig. 1A) was automatically analyzed by Zplot/Zview.…”

Pre-suckling calcium supplementation effectively prevents lactation-induced osteopenia in rats

“…We have recently reported that in lactating rats the pituitary-derived lactogenic hormone prolactin (PRL) is the salient factor that regulates bone turnover and osteoclast-mediated bone resorption in lactation (33). Meanwhile, PRL also dramatically enhances duodenal calcium absorption, which provides additional calcium to the body (3). PRL as an important regulator of lactogenesis, thus helping supply free ionized calcium from either bone or diet for production of milk, the principal calcium source of the newborn.…”

“…The lack of positive effect could be explained by the fact that the fractional calcium absorption is as low as 15-20% without appropriate hormonal stimulation, e.g., PRL (particularly during the suckling-induced PRL surge) or 1,25-dihydroxyvitamin D 3 . Moreover, excessive calcium in the intestinal lumen often precipitates as water-insoluble complexes after exposure to luminal alkaline pH.…”