Distribution of gamma-glutamyl transpeptidase and glutaminase isoenzymes in the rabbit single nephron.

The Rabbit Kidney Tubule Simultaneously Degrades and Synthesizes Glutamate

“…Synthesis of Glutamine-Although we recently presented some evidence that, in the presence of glucose plus NH 4 Cl, glutamine accumulation resulting from the action of glutamine synthetase was accompanied by glutamine degradation by glutaminase (6), we obtained in the present study no evidence that glutaminase operated; therefore, we were unable to quantify flux through the latter enzyme which is present along the entire length of the rabbit proximal tubule (3).…”

“…Both in the absence and the presence of acetate, the labelings of the C-1 (singlet) of glutamate and glutamine and of alanine were almost identical when [5-13 C]glutamate or [1,2-13 C]glutamate was the substrate. Tables V and VI also show that, with [5-13 C]glutamate and [1,2-13 C]glutamate as substrate, both in the absence and the presence of acetate, the labeling of the C-1 (singlet) of glutamate, glutamine, and alanine was virtually half that of the C-2 of glutamate, glutamine, and alanine when [3][4][5][6][7][8][9][10][11][12][13] C]glutamate was the substrate (see Table IV). …”

“…Since the C-2 and the C-3 of the oxaloacetate derived from the added [3-13 C]glutamate were converted at the same rates to the C-3 and C-2 (respectively) of the glutamate synthesized and therefore to the C-3 and C-2 of the glutamine derived from the latter glutamate, one may calculate that with glutamate as sole substrate, a mean value of 67 mol/g dry wt of glutamine arose directly from the added [3-13 C]glutamate, whereas 10.8 mol/g dry wt of [3-13 C]glutamine derived from synthesized [3][4][5][6][7][8][9][10][11][12][13] C]glutamate (see Table IV); in the presence of [3-13 C]glutamate plus acetate, the corresponding values are 34.6 and 11.3 mol/g dry wt, respectively. The latter values obtained for estimating the direct accumulation of glutamine from added [3-13 C]glutamate in the absence and the presence of acetate are in relatively good agreement with those obtained by measuring the accumulation of [5-13 C]glutamine from [5-13 C]glutamate (Table V) as well as by measuring the multiplets (spin-spin 13 C coupling of C-1 and C-2) resulting from the synthesis of [1,2-13 C]glutamine from [1,2-…”

“…When [3][4][5][6][7][8][9][10][11][12][13] C]glutamate was the substrate in the absence and the presence of acetate, the labeling (in mol/g dry wt) of the different carbons of glucose (␣ ϩ ␤ anomers) was as follows: C-1, 2.2 Ϯ 0.5 and 3.4 Ϯ 0.2; C-6, 1.8 Ϯ 0.5 and 2.6 Ϯ 0.1; C-2, 1.7 Ϯ 0.6 and 2.6 Ϯ 0.4; C-5, 2.5 Ϯ 0.9 and 4.5 Ϯ 0.2, respectively; the C-3 and C-4 were not enriched. When [5-13 C]-and [1,2-13 C]glutamate were the substrates, the C-3 and C-4 of glucose were enriched only in the presence of acetate; the values were 2.0 Ϯ 0.4 and 1.1 Ϯ 0.1 for the C-3, respectively; the corresponding values for the C-4 were 2.4 Ϯ 0.5 and 1.7 Ϯ 0.2, respectively.…”

Intranephron Distribution of Epidermal Growth Factor Immunoreactivity in the Mouse

“…High protein contents in the proximal tubule (divided into two parts; convoluted and straight tubules) were noted. These values of protein contents were comparable with those in rats and rab bits, as previously reported from our labora tory [9,10]. Thus, specific EGF contents of medullary and cortical thick ascending limbs of Henlc's loop were disclosed as highest, followed by the glomerulus and the distallylocated segments such as the distal tubules and conical and medullary collecting tubules.…”