Biochemical evidence for a cytoplasmic 1 alpha,25-dihydroxyvitamin d3 receptor-like protein in rat yolk sac.

J.L Danan,A.C Delorme,P Cuisinier-Gleizes

doi:10.1016/s0021-9258(19)69332-4

Abstract

The yolk sac in rats is an organ of exchanges between the mother and fetus. A vitamin D-dependent calcium-binding protein (CaBP) has been recently described in this organ. This led us to investigate the presence of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) receptor-like proteins in the yolk sac cytosol. For this purpose we have utilized sucrose gradient centrifugation, Scatchard analysis, and DNA-cellulose chromatography. Our results show that cytosol prepared from rat yolk sacs contains a 3.3 S binding protein for 1,25-(OH)2D3. The binding is a highly specific, saturable process with high affinity(2 X 10(-10) M at 25 degrees C). The sterol-protein complex binds to DNA-cellulose. The 1,25-(OH)2D3 binding protein is present in the yolk sac from at least the 15th day until the 21st day of gestation. In contrast, such a binding protein is not found in the amnion, the other component of fetal membranes. The biochemical parameters of the 1,25-(OH)2D3 binding protein in the yolk sac are similar to those of 1,25-(OH)2D3 cytosolic receptors in vitamin D target organs. This strongly suggests that the 3.3 S protein in the yolk sac may function as a specific receptor, indicating that this organ may be a new target organ for vitamin D.

Highlights

Our results show that cytosol prepared from rat yolk an embryonic precursor of the intestine [15], prompted us to investigate the presence of 1,25-(OH)2D3 cytosolic receptors in this tissue
Unlabeled 25-OHD3 was a gift from Roussel Uclaf (France) while 24,25-dihydroxyvitamin D3 (24,25-(OH)2D3) and 1,25-(OH)2D3 were kindly obtained from Hoffreceptors in vitamin D target organs
Sucrose Gradient Analysis-Cytosol from rat yolk sacs was examined for the presence of a 1,25-(OH)2D3 specific binding protein by sucrose density gradient analysis

Summary

Introduction

Suggests that the 3.3 S protein in the yolk sac may Tissue Preparation-Unless otherwise stated, all experiments function as a specific receptor, indicating that this or- were performed on rats which were in their 18th day of gestation. DNA-Cellulose Chromatography-Yolk sac cytosols were incubated with 1 nm 1,25-(OH)2[3H1D3 in presence of 10 nM unlabeled 25- Binding Studies-Cytosol was prepared using yolk sacs pooled from 8 pregnant rats.

Results

Conclusion