Abstract
Lactose exists only in milk as a product of the mammary gland and its considerable amount is found in the milk of many animals except in that of ocean animals, such as whales and seals (1). Lactose is suggested to play an important role for the biosynthesis of galactocerebroside (2-4) (Fig. 1).
On the other hand, lactose added to milk has an undesirable character. First, there are many reports on sucklings about the addition of lactose to the milk being deleterious. Second, many clinicians have experimented with congenital or acquired intolerances for lactose ingestion. Third, it has been reported by Tamura (5) that dyspepsia with diarrhoea in suckling is induced by the accumulation of galactose-l-phosphate, the inhibition of lactose activity in the intestinal wall and an acceleration of permeability of the intestine.
Riggs and Beaty (6) reported that animals, which are fed on a hyper-lactose diet, are arrested in their growth, and some disorder of the intestine, especially diarrhoea, occurs in mammalians and birds. Mitchell and Day (8) found that the cataract occurs in the rat. Takuma and Takayama (9) and Tamura and Ogihara (10) also observed that cataract and a disorder of nutrition of rat caused by lactose are prevented by an addition of whey in the diet (Fig. 2).
The metabolism of lactose mentioned by Bihler and Crane (11) is as follows: lactose was decomposed to galactose and lactose, and turned in cytoplasma with sodium ion. Then, glucose was availed in glycolytic or non-glycolytic metabolism, and galactose was metabolized through the Leloir enzyme system (1) (Fig. 3).
Now, we can take the view that the inhibition of enzymes occurred in the Leloir way in the above-mentioned disease of sucklings and rats. The authors studied the activity of the Leloir enzyme system in rats fed on a hyperlactose or a hypergalactose diet, and the effect of whey including the promoting factor of lactose or galactose metabolism upon this system.
