Calcium as a possible modulator of Kupffer cell phagocytic function by regulating liver-specific opsonic activity.
Recently we described some properties of organ-specific serum opsonins which differentiate between liver- and spleen-specific opsonic activities, and reported that, on dialysis of serum, its liver opsonic activity is enhanced by 2- to 3-fold, whereas spleen-specific activity is reduced by 20-30% of that of control serum (Moghimi, S.M. and Patel, H.M. (1989) Biochim. Biophys. Acta 984, 379-383). This observation suggests that serum contains dialysable factors which regulate liver- as well as spleen-specific opsonic activities. Our results from EGTA-treated serum suggest that dialysable factor(s) could be divalent cations such as Ca2+, Mn2+, Mg2+ or Co2+, and among them, calcium may be the key regulatory factor for liver-specific opsonic activity. The regulatory mechanism of spleen-specific opsonic activity seems to be complex, since addition of dialysate or calcium or magnesium to the dialysed serum does not restore its activity; probably the removal of divalent cations has induced an irreversible conformational change in spleen-specific opsonin. In conclusion, we propose that the blood calcium concentration may play an important role in modulating hepatic phagocytic function by modifying liver-specific opsonic activity in serum. An increase in the physiological concentration of calcium will suppress and a decrease will enhance this opsonic activity.
Moghimi
S M
SM
Department of Biochemistry, Charing Cross and Westminister Medical School, London, U.K.
Patel
H M
HM
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D004533:Egtazic Acid / Q000494:pharmacology; D007728:Kupffer Cells / Q000276:immunology*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000494:pharmacology; D010587:Phagocytosis; D051381:Rats; D013154:Spleen / Q000276:immunology
D008345:Manganese; D004533:Egtazic Acid; D008274:Magnesium; D002118:Calcium