1. Biochemical properties of human renin expressed in transgenic mice (hRN8-12 mice) carrying the human renin gene (Fukamizu et al. Biochem Biophys Res Commun 1989; 165: 826–32) were examined. The optimum pH of the enzymic activity against human angiotensinogen was 5.5 for both plasma and renal human renin in the hRN8-12 mice. Plasma concentrations of human active and inactive renin in the plasma of hRN8-12 mice were 16.7 ± 2.8 and 79.9 ± 14.0 pmol of angiotensin 1 h−1 ml−1, respectively, thereby indicating that the predominant form of plasma human renin is the inactive form, as is the case in humans.
2. The molecular masses of plasma human active and inactive renin and renal human active renin in the hRN8-12 mice were estimated to be 46kDa, 48kDa and 44kDa, respectively, as determined by h.p.l.c. on G3,000SW.
3. Human renin in the hRN8-12 mouse kidney was bound to a concanavalin A-Sepharose column, and was eluted with α-methyl-d-mannoside, showing that this renin is glycosylated, as is native human renin.
4. Low sodium treatment of the hRN8-12 mice for 2 weeks increased plasma human active renin, renal human renin and renal human renin mRNA levels by 2.6-, 3.8- and 2.8-fold, respectively. Thus, the biosynthesis and secretion of renal human renin in these transgenic mice are obviously stimulated by sodium depletion.