Whole-body autoradiographic study of vitamin K distribution in rat.

Vitamin K group is known as an anti-haemorrhagic vitamin and has a common skeleton of 2-methyl-1,4-naphthoquinone. There are several homologs which differ in the alkyl side chain at 3-position of naphthoquinone ring. Of these homologs, vitamin K2(20) (K2) which has a geranyl-linalyl side chain is considered to be a physiologically active type of this vitamin, since Martius, et al.2) reported that the administered vitamins K is converted to this type of homolog in pigeon chicken and rat. We reported the tissue distribution and metabolic fate of K2 by isotopic tracer techniques.3) However, the determination of radioactivity by combustion method4) is technically difficult for several tissues. In the present paper, we report the distribution of K2 in rats by whole-body autoradiography which is advantage in determining the intuitively fine distribution of radioactivity. And the results are compared with those of naturally occurring vitamin K1 and synthetic vitamin, vitamin K3. We also studied the bile excretion of these vitamins, because of their less urinary excretion and high radioactivity in intestinal content.