Mononuclear cells from human neonates are partially resistant to the action of 1,25-dihydroxyvitamin D.
1,25-Dihydroxyvitamin D [1,25-(OH)2D] inhibits mitogen-induced proliferation of lymphocytes by a receptor-mediated mechanism. Peripheral blood lymphocytes may serve as a model for detecting hereditary defects in the response of classical target organs to 1,25-(OH)2D. Delayed bone mineralization and deficient intestinal calcium absorption are common in low birth weight formula-fed infants. The defect in calcium absorption exists despite normal or even elevated serum 1,25-(OH)2D levels, suggesting partial end-organ resistance to the hormone. We assessed the response to 1,25-(OH)2D of activated mononuclear cells obtained from cord blood of fullterm and preterm infants and from peripheral blood of adults. We found that the inhibitory effect of 1,25-(OH)2D on mitogen-induced [3H]thymidine incorporation was significantly less [mean, 34 +/- 8% (+/- SE)] in mononuclear cells from neonates (independent of gestational age) compared to mononuclear cells from adults (66 +/- 5%; P less than 0.001). This difference in the inhibitory effect was not due to a smaller number of high affinity receptors for 1,25-(OH)2D in activated cord blood lymphocytes. We conclude that the coupling between the receptors for 1,25-(OH)2D and the biological response in neonates is less efficient than that in adults.
Ravid
A
A
Rogoff Medical Research Institute, Beilinson Medical Center, Petah-Tikva, Israel.
Koren
R
R
Rotem
C
C
Amir
Y
Y
Reisner
S
S
Novogrodsky
A
A
Liberman
U A
UA
D000328:Adult; D000375:Aging / Q000276:immunology; D002117:Calcitriol / Q000494:pharmacology*; D004351:Drug Resistance; D005260:Female; D005312:Fetal Blood / Q000276:immunology; D006801:Humans; D007231:Infant, Newborn / Q000276:immunology*; D007234:Infant, Premature / Q000276:immunology; D007963:Leukocytes, Mononuclear / Q000187:drug effects*; D008213:Lymphocyte Activation / Q000187:drug effects*; D008297:Male; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000378:metabolism; D013936:Thymidine / Q000097:blood
D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D002117:Calcitriol; D013936:Thymidine