Dehydrogenases, nucleic acids and soluble proteins in mammary gland of the Mongolian gerbil during pregnancy, lactation and involution

1. 1. The activities of lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G-6-PDH) and glycerol-3-phosphate dehydrogenase (G-3-PDH), as well as the isoenzymes of LDH and the two molecular forms of MDH have been assayed in mammary tissue of the Mongolian gerbil, Meriones unguiculatus, during pregnancy, lactation and involution. In addition, the amounts of DNA, RNA and soluble proteins were determined. 2. 2. The results differed in some respects from the principal pattern seen in other small rodents. The activity of LDH dominated over the activity of MDH during all three stages, in contrast to e.g. the rat. Moreover, the distribution of the LDH isoenzymes, in contrast to the rat, showed a pattern with a pronounced dominance of LDH 5. The relative activities of S-MDH and M-MDH were almost equal during pregnancy, lactation and involution. As regards the nucleic acids, the peak value of the quotient RNA/DNA obtained during lactation was higher than the quotient from the mammary gland of the rat, mouse or hamster. 3. 3. Mammary glands from the anterior and posterior parts of the body were analysed separately, and in general, the activities of the dehydrogenases as well as the amount of protein and RNA were higher in the anterior glands. The reason for these divergencies is not known, but may be due to differences in structure and function between the glands. 4. 4. During late involution, there was an increase in the activities of LDH, MDH and G-3-PDH, while G-6-PDH remained at a low level. This difference was supposed to be a result of hormonal influence on the mammary tissue.