Immunochemical studies on the putative plasmalemmal receptor for 1,25-dihydroxyvitamin D-3. III. Vitamin D status

The effect of vitamin D status an levels of the putative 1,25(OH)(2)D-3 mem brane receptor (pmVDR) was studied in chick intestine, kidney, and brain. W estern analyses and assays for specific [H-3]1,25(OH)(2)D-3 binding indicat ed that, in intestine, pmVDR levels were greatest in -D chicks relative to +1,25D and +D animals (P < 0.05). In kidney, protein levels and specific bi nding followed the order +D > +1,25D, -D. In brain, vitamin D status did no t affect protein levels or specific binding levels. In tissue from normal c hicks, both protein and specific binding followed the order of intestine > kidney > brain membranes. Intestinal cells were further evaluated for the e ffect of 1,25(OH)(2)D-3 on selected "rapid responses." Extrusion of Ca-45 i n response to 130 pM 1,25(OH)(2)D-3 in vitro was greater in cells from -D c hicks than from +1,25D or normal birds. Analyses of signal transduction eve nts revealed diminished hormone-induced intracellular calcium oscillations (as assessed by fura-2 fluorescence), and lack of steroid-enhanced protein kinase (PK) A activity in intestinal epithelial cells from -D chicks relati ve to +D chicks. PK C activation by 130 pM 1,25(OH),D,was approximately two fold in cells from +D or -D chicks. The combined results indicate that vita min D status differentially affects the pmVDR in intestine, kidney, and bra in. In intestine, vitamin D deficiency differentially affects Ca-45 handlin g, intracellular calcium oscillations, PK A and PK C activities in response to 1,25(OH)(2)D-3. (C) 2000 Elsevier Science Inc. All rights reserved.