抄録
There have been some suggestions as to how to prevent babies from vitamin K deficiency. However, the endogenous form of vitamin K is not known yet. Also it is not known whether vitamin K_1 is more effective than K_2 (MK_n) or vice versa. It has been recommended by the American Academy of Pediatrics that K_1 should be administered parenterally to all newborn infants as prophylaxis. In contrast to that, in Japan, K_2 (MK-4) is generally administered as injection or syrup for babies. In this study, to find out the change of vitamin Ks in plasma and brain tissue, we measured the concentrations of K_1 and MK-4 in K_1 and MK-4 administered and control rats. In brain tissue of control group, MK-4 level was 0.55×10^<-3> nmol/g and K_1 was not detected (<5 ×10^<-4> nmol/g). K_1 and MK-4 levels in plasma of control rats were below the detection limits. In K_1 administered group, MK-4 concentrations were significantly higher in both plasma and brain tissue than those in control. On the other hand, K_1 was not detected in MK-4 administered group. We suppose K_1 may be changed to MK-4 but MK-4 is not changed to K_1, so that MK-4 may be more preferable than K_1. Judging from these points, MK-4 should be prefered as prophylactic vitamin K therapy to babies.
