Effect of growth and maturation on membrane-initiated actions of 1,25-dihydroxyvitamin D3-II: calcium transport, receptor kinetics, and signal transduction in intestine of female chickens.
We recently reported (Larsson and Nemere [2003]: Endocrinology 144:1726) the effects of growth and maturation on 1,25(OH)2D3-membrane initiated effects in the intestine of male chickens. Here we extend our observations to studies on females with two stages of high calcium demand: growth (7-14 weeks) and egg laying (28-58 weeks). The rapid stimulatory effect of 130 pM 1,25(OH)2D3 on calcium transport was assessed as a physiological response in perfused duodena of 7-, 14-, 28-, and 58-week-old chickens, and determined to be 308%, 184%, 170%, and 153%, respectively, of corresponding controls after 40 min. Saturation analyses of [3H]1,25(OH)2D3 binding to nuclear vitamin D receptor (VDR) indicated an absence of cooperative binding, no changes in dissociation constant (Kd) with age, and an increase in maximum binding capacity (Bmax) between 7-week birds and older age groups. Analyses of saturable binding of [3H]1,25(OH)2D3 to the membrane associated rapid response steroid binding protein (1,25D3-MARRS bp) in basal lateral membranes (BLM), indicated cooperative binding, and an increase in both Bmax and Kd with age. No changes in the age-related expression of 1,25D3-MARRS bp were found, as judged by Western analyses, suggesting that a shift in ligand binding to lower affinity membrane components accounted for the increase in calculated Bmax. Basal levels of protein kinase C (PKC) activity decreased with age, as did hormone enhancement of activity. Basal levels of protein kinase A (PKA) activity remained constant with age, while the magnitude of hormone stimulation increased. Comparison of dose-response curves for ion transport and kinase activities in 7-week chicks suggested that PKC mediates phosphate transport while PKA mediates calcium transport. Thus, the age-related loss of calcium transport is most likely related to loss of PKC-mediated phosphate transport.
Larsson
Birgitta
B
Utah State University, Department of Nutrition and Food Sciences and the Biotechnology and Genomics Research Center, Logan, Utah 84322-8700, USA.
Nemere
Ilka
I
D000375:Aging / Q000502:physiology; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000378:metabolism / Q000494:pharmacology*; D002455:Cell Division; D002462:Cell Membrane; D002645:Chickens; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005260:Female; D007413:Intestinal Mucosa / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*
D002120:Calcium Channel Agonists; D018167:Receptors, Calcitriol; C118756:dihydroxy-vitamin D3; D014807:Vitamin D; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D002117:Calcitriol; D002118:Calcium