Role of changes in membrane lipid structure in the action of 1,25-dihydroxyvitamin D3
Rasmussen, H.; Matsumoto, T.; Fontaine, O.; Goodman, D.B.
Federation Proceedings 41(1): 72-77
1982
ISSN/ISBN: 0014-9446 PMID: 6895735 Document Number: 188055
1,25-Dihydroxycholecalciferol (1,25-DHCC) stimulates the entry of calcium into the duodenal mucosal cell of chickens by a mechanism which does not require the synthesis of new protein. Isolated brush-border membrane vesicles (BBMV) from these cells were used to study the mechanism by which 1,25-DHCC acts. 1,25-DHCC caused an increase in Ca uptake into BBMV. This Ca uptake was a saturable process. Addition of the methyl ester of cis-vaccenic acid to BBMV in vitro resulted in a specific increase in Ca uptake into vesicles from chickens deprived of vitamin D but not in those from chickens given 1,25-DHCC. 1,25-DHCC resulted in an increase in the synthesis of phosphatidylcholine (PC) de novo and an increase in the total PC content of the brush-border membrane. It also increased the turnover of fatty acids into PC, which resulted in an increase in the content of polyunsaturated fatty acids in the PC fraction. The changes in lipid structure and turnover preceded or occurred simultaneously with the change in Ca transport rate, and neither was blocked by cycloheximide. It is proposed that the primary mechanism by which 1,25-DHCC regulates Ca transport across the luminal membrane of the enterocyte is by inducing a specific change in membrane PC content and structure, which results in an increase in membrane fluidity and thereby an increase in Ca transport rate.