Kidney independent serine synthesis in the rat. Effect of dietary serine and glycine restriction

The potential role of the kidney in renal serine synthesis was elucidated in rats following dietary serine as well as serine and glycine depletion for 6 weeks. Serine deficient diet caused a significant rise in blood serine and glycine values. In contrast, blood glycine concentration decreased significantly following serine and glycine depletion, whereas blood serine levels remained unchanged. Bilateral nephrectomy caused a significant decrease of blood serine values of control and serine deficient rats. Serine concentration, however, was not affected by bilateral nephrectomy following serine and glycine deficiency indicating kidney-independent serine synthesis under these conditions. There was a significant increase of blood lactate and pyruvate levels under serine and serine/glycine deficient diet compared with control animals, whereas blood ketone bodies fell. In contrast, 24 h after bilateral nephrectomy blood ketone bodies rose and blood lactate and pyruvate concentrations decreased significantly. 24 h after bilateral nephrectomy there was a marked rise in blood citrate values of female rats compared with male animals indicating sex dependency of kidney citrate metabolism in the rat.