Regulation of compensatory kidney hypertrophy by its own products

Rapid resolution of proteinuria of native kidney origin following live donor renal transplantation

To assess the contribution of the protein content of urine from the native kidneys to post-transplant proteinuria, we prospectively studied 14 live donor transplant recipients with a pre-transplant random urine protein to creatinine ratio (UPr:Cr) >0.5. Seven patients received preemptive transplants, and seven patients were on dialysis pre-transplant (with residual urine output). Resolution of proteinuria was defined as UPr:Cr < 0.2. Immunosuppression consisted of tacrolimus, mycophenolate mofetil and corticosteroids. Anti-hypertensive drugs that might reduce proteinuria were avoided during the study. The serum creatinine was 8.7 +/- 0.7 mg/dL pre-transplant, and the nadir post-transplant serum creatinine was 1.4 +/- 0.1 mg/dL. The pre-transplant UPr:Cr ranged between 0.5 and 9.2 (mean = 2.9 +/- 0.6). The UPr:Cr decreased to <0.2 in all 14 patients at a mean of 4.5 weeks post-transplant (range 1-10 weeks). In conclusion, in live donor renal transplant recipients with immediate graft function, proteinuria of native kidney origin resolves in the early post-transplant period. After the immediate post-transplant period, proteinuria cannot be attributed to the native kidneys, and work up for proteinuria should focus on the allograft.

Role of insulin-like growth factor binding proteins in human post-nephrectomy proximal tubule cells

1. In order to determine the role of the insulin-like growth factor-I (IGF-I)/IGF binding protein (IGFBP) axis in the augmentation of tubule growth and function following reductions in nephron mass, primary cultures of human proximal tubule cells (PTCs) were generated from the histologically normal sections of ten surgically removed kidneys. 2. PTC hypertrophy (cellular protein content), DNA synthesis (thymidine incorporation) and apical sodium-hydrogen exchange (NHE) activity (ethylisopropylamiloride-sensitive apical 22Na+ uptake) were measured following 24 h incubation in media supplemented with 10 % pre- or post-nephrectomy sera obtained from these patients. The results were compared with the effects of pre- and post-operative control sera collected from seven patients undergoing retroperitoneal operations not involving removal of renal tissue. 3. Day 1 post-nephrectomy sera promoted a significant 73 % increase in apical NHE activity, which was accompanied by a significant increase in PTC binding of 125I-IGF-I (post- vs. pre-nephrectomy, 163 +/- 6 vs. 142 +/- 4 fmol (mg protein)-1; P < 0.05). Subsequent post-nephrectomy sera significantly stimulated PTC protein content and thymidine incorporation, peaking at day 7 (127.7 +/- 14.0 and 118.4 +/- 9.0 % of pre-nephrectomy values, respectively; P < 0.05). The growth effects were cell specific, as they were not observed with renal cortical fibroblasts. No change was detected in any of these measured variables following exposure to control sera. 4. Serum IGF-I and IGFBP-1 levels did not significantly change over time or between groups. IGFBP-3 levels progressively decreased in both control and nephrectomized sera from pre-operative values of 3580 +/- 305 and 3360 +/- 217 ng ml-1, respectively, to 2670 +/- 341 and 2600 +/- 347 ng ml-1 at 1 week post-operation. Serum IGFBP-2 levels increased to a comparable extent in both controls (day 0 vs. day 7, 2940 +/- 1024 vs. 7010 +/- 2520 ng ml-1; P < 0.01) and nephrectomized patients (day 0 vs. day 7, 3070 +/- 656 vs. 9130 +/- 2010 ng ml-1; P < 0.01). 5. The results indicate that nephrectomy engenders the elaboration of one or more humoral factor(s), which promotes increased binding of IGF-I to PTCs and which may in turn specifically stimulate PTC Na+ transport and growth.

A study of growth regulators of renal cortical tubular cells in the rabbit liver

Two growth regulators, a growth stimulator for cultured renal tubular cells and a growth inhibitor, were observed in this study in rabbit liver homogenate after a unilateral nephrectomy. These regulators appeared in the liver on the third day after this nephrectomy, decreased on the seventh day, and disappeared by the fourteenth day. The growth stimulatory activity, termed a tubular cell growth factor (TuCGF), was a heat- and acid stable 15 to 20 KDa protein. The additive effects of TuCGF on the epidermal growth factor (EGF), the insulin-like growth factor-I (IGF-I), and the fibroblast growth factor (FGF) were observed; the results suggest that TuCGF differs from EGF, IGF-I, or FGF. In contrast, the growth inhibitory activity, termed a tubular cell growth inhibitor (TuCGI), was a heat- and acid-labile protein with a molecular weight of about 150 to 200 KDa. This factor potently inhibited the DNA synthesis of tubular cells in the presence of insulin and EGF. These results suggest that TuCGI is not identical with transforming growth factor-beta (TGF-beta). The regulation of these activities by target cell density is also discussed.

Relation between renal and hepatic excretion of drugs: III. Comparison of various methods reducing the renal or hepatic excretory capacity of rats

In previous investigations bilateral nephrectomy (NX) and bile duct ligation (DL) were used to interrupt the renal or biliary excretion route, respectively. But competent doubt arose concerning the comparability of both interferences. In the case of DL the liver could influence the possible compensatory increase of renal excretion capacity; after removal of both kidneys such feedback on the liver is impossible. Therefore the corresponding operations were tested: bilateral ureter obstruction (UO) and so-called functional hepatectomy (fHX) caused by ligation of the porta hepatis. The time courses of a compensatory intensification of the excretory function of liver or kidney have been demonstrated. The following general conclusions can be drawn: fHX is characterized by some drawbacks because of its severe negative systemic effects. Thus DL should be preferred because the compensatory renal excretion capacity can be investigated without a significant reduction of the animal's vital forces. In contrast, NX seems to be the method of choice interrupting renal excretion. It is possible to remove both kidneys without a disturbance of other organ functions and the unpredictable effects of the hydronephrotic kidneys after UO on the whole organism are excluded. At least it is optimal to perform clearance studies approximately 24 h after both NX/UO or DL, because already at this time the phenomena of compensation have become maximal.

Kidney function after unilateral nephrectomy

Immediately after unilateral nephrectomy ( uNX ) some different mechanisms of compensatory adaptation begin to act followed by a restoration of sufficient kidney function in a short time period. Beside biochemical changes early compensatory hypertrophy of the remaining kidney occurs. Simultaneously, functional adaptations of renal blood flow, glomerular filtration and exertion of electrolyte and xenobiotics take place. With a suitable pretreatment it is principally possible to accelerate the regeneration phase. Thus the phase of reduced excretion capacity of tubularly secreted xenobiotics after removal of one kidney can be shortened or prevented.

Renotropic growth factor found in cancer patient sera after removal of cancer-bearing kidney

We have used two sets of primary human kidney culture systems for assaying human renotropic growth factor in day 5 postnephrectomized human sera. The first set of primary kidney cell cultures was prepared from one hydronephrotic kidney and used for assaying the renotropic growth stimulating activity of six kidney cancer patients sera simultaneously. The level of renotropic growth-stimulating activity varies from patient to patient. The postnephrectomized sera of three patients showed rather small (27 to 68%) increase over their prenephrectomized sera. The postnephrectomized sera of the remaining three patients showed a much greater (2.69- to 3.19-fold) increase over their prenephrectomized sera. Variation in the growth-stimulating activities produced in these uninephrectomized kidney cancer patients is most probably due to different levels of renal function loss by removal of the cancer-bearing kidney. Each cancer-bearing kidney has a different proportion of healthy kidney region to diseased (nonfunctional) region. The second set of primary kidney cell cultures was prepared from a healthy noncancerous region of a cancer-bearing kidney and used to assay for renotropic growth-stimulating activities in two different unilaterally nephrectomized kidney transplantation donor sera. Increased levels of growth-stimulating activity are quite similar and high (4.19- to 4.79-fold increase above their prenephrectomized sera). These high and similar assay values of the renotropic growth factor produced in two healthy humans suggest the sensitivity and reliability of the assay method with the use of the noncancerous cells from the cancer-bearing kidney.

In vitro evidence from tissue cultures to prove existence of rabbit and human renotropic growth factor

When synchronized primary rabbit kidney monolayer cell cultures were incubated with a medium that contained uninephrectomized rabbit serum, the incorporation of tritiated thymidine into DNA was much greater than that with a medium that contained normal rabbit serum. The maximal growth-stimulating activity of uninephrectomized rabbit serum on thymidine incorporation into confluent monolayer cultures and sparsely cultured cells was increased approximately two- and fivefold, respectively, above that of normal serum. We conclude that uninephrectomized sera contain a growth-stimulating factor. Similarly, sera from a uninephrectomized human kidney donor and a cancer patient stimulated primary human kidney cell cultures to incorporate tritiated thymidine at levels far beyond those with their prenephrectomized sera. The maximal growth-stimulating activities of uninephrectomized human sera with confluent monolayer cultures and sparsely cultured cells were approximately six- and 13-fold, respectively, above those with the prenephrectomized sera. Thus, the maximal growth-stimulating activity in uninephrectomized human sera was much greater than that in uninephrectomized rabbit sera. Differences in the maximal growth-stimulating activities may be due to differences in the relative number of cell types, for example, epithelial versus fibroblast, present in these kidney cell cultures. By the use of primary cultured cells from other organs such as rabbit skin and human prostate and primary kidney cultures from three species (rabbit, human, and hamster), the growth-stimulating factor in uninephrectomized sera showed organ specificity, that is, renotropic and species specificity in this in vitro assay system.(ABSTRACT TRUNCATED AT 250 WORDS)

The control of liver regeneration after partial hepatectomy in the rat

1. Normal rat liver slices were incubated for 24 h in culture medium to which had been added freeze-dried plasma, prepared from the blood of rats which had undergone partial hepatectomy (60-70% of liver removed) 10 min, 4 or 24 h previously. No changes in the dry weight of the slices were observed. 2. Similarly, there were no changes in the dry weight or protein content of incubated liver slices when freeze-dried plasma prepared from the blood of rats unilaterally nephrectomized 10 min, 4 or 24 h previously was added to the culture medium. 3. Slices from the remaining liver stump, taken 4 h after partial hepatectomy (60-70% of liver removed) and incubated for 4 h in culture medium, did not release a factor capable of increasing the dry weight of normal liver slices incubated in the same medium. 4. After partial hepatectomy (60-70% of liver removed), there was no increase of guanosine 3':5'-cyclic monophosphate in the remaining part of the liver. 5. No measurable amount of esterase activity was found in normal liver or in the remaining liver stump after partial hepatectomy (60-70% of liver removed). 6. It is suggested that the stimulatory mechanism for liver regeneration is of a different nature from that involved in compensatory renal hypertrophy.

Origin of the humoral factor responsible for compensatory renal hypertrophy

1. Rats were unilaterally nephrectomized and the remaining kidney was removed 10 min after the operation.2. Cortical slices from both kidneys were incubated in culture medium in the presence of freeze-dried plasma from a control animal, for 4 hr. When renal cortical slices from a normal animal were now added to and incubated in the medium in which cortical slices from the remaining kidney (i.e. the kidney removed 10 min after unilateral nephrectomy) had been incubated, they showed an increase of protein content and dry weight. This increase did not occur when slices from normal kidneys were incubated in culture medium in which the first kidney had been incubated.3. The increase of protein content and dry weight of cortical slices from normal kidneys did not occur when incubated in culture medium in which cortical slices from the remaining kidney had been incubated when freeze-dried plasma from normal rats had been substituted by freeze-dried plasma from anephric rats.4. Since normal plasma which does not normally promote protein accretion in normal cortical slices in vitro can do so after it has been incubated with cortical slices from a kidney removed 10 min after unilateral nephrectomy, it is suggested that normal plasma contains a precursor of renal origin which is ;activated' when in the presence of a remaining kidney removed shortly after unilateral nephrectomy.

Presence of renotrophic factor in plasma of unilaterally nephrectomized rats

1. Renal cortical slices cut in two halves were incubated separately in culture medium. One half slice was used as control while the other half was treated experimentally. After incubation, their dry weights and/or their protein content were estimated. 2. Addition to half cortical slices of 30 micrograms mg-1 of freeze-dried plasma from rats killed 24 hr after unilateral nephrectomy resulted in an increase of dry weight or protein content of the order of some 10% after 4-8 hr incubation. 3. The effect of freeze-dried plasma from rats killed 24 hr after unilateral nephrectomy was specific to the renal cortex. When added to half slices from either the renal medulla or the liver there were no changes in their dry weight. 4. Addition of 30 micrograms mg-1 of freeze-dried plasma from rats killed 24 hr after bilateral nephrectomy had no significant effect on the dry weight of half cortical slices incubated for various periods of time, from 4 to 48 hr. 5. The renotrophic activity of plasma from unilaterally nephrectomized rats, killed 24 hr after the operation, appears to be metabolized or destroyed by incubation with cortical slices in 4 hr. 6. Freeze-dried plasma from normal unilaterally nephrectomized rats produced an increase dry weight when incubated for 4 hr with half cortical slices from early (3 days) hypophysectomized rats. When incubated with half cortical slices from late (23 days) hypophysectomized rats, the increase in dry weight was about 2 times as great as that observed with cortical slices from normal animals. 7. The possible reason for the production of renotrophic activity in plasma of unilaterally nephrectomized rats, and for its absence in plasma of anephric animals, is discussed.

The measurement of colonic mucosal-submucosal blood flow in man

1. A method is described for the measurement of colonic mucosal-submucosal blood flow in man, by studying surgically created colostomies. 2. A local radioisotopic clearance technique utilizing a stable preparation of [125I]4-iodoantipyrine is employed. The indicator is injected directly into the colostomy under study and its gamma emission is recorded by a scintillation detector. 3. A radioautographic study was carried out at laparotomy in humans to facilitate the interpretation of the recorded washout curves. This demonstrated that the tracer was cleared from both the mucosa and submucosa throughout the period of study. 4. Mucosal-submucosal blood flow was calculated according to Kety (1949) from the monoexponential clearance curves obtained, and amounted to 31.7 +/- 11 ml./min. 100 g (S.D. of an observation, n = 30). 5. The results from two consecutive measurements in seventeen patients showed that the mean change between first and second readings was not significant (t test). In addition the between-patient variation (12.2) was significantly greater than the within-patient variation (2.6) for consecutive recordings (F test; P less than 0.01). 6. The within-patient between-days variation (12.9; n = 10) was found to be similar to the between-patient variation. 7. It is concluded that the technique permits measurement of local colonic blood flow in man and by consecutive measurements, it may be used to evaluate local changes in blood flow following reflex or pharmacological stimulation.

Compensatory renal hypertrophy in hypophysectomized rats

1. After hypophysectomy, both body and kidney weights fall, but at different rates. The rate at which the kidney decreases in weight is faster than that of the whole body.2. Seven days after unilateral nephrectomy, the dry weight of the remaining kidney of hypophysectomized rats, with the exception of rats which had been hypophysectomized for 2 days only, was always heavier than the kidney of control hypophysectomized rats of similar body weight.3. The difference between the dry weight of kidneys of unilaterally nephrectomized hypophysectomized and control hypophysectomized rats increased from 15% in early hypophysectomized (9 days) to about 35% in late hypophysectomized animals (23 days).4. The implantation of renal cortical cells from 2 day hypophysectomized rats into unilaterally nephrectomized control litter-mates inhibited compensatory renal hypertrophy in the latter. When a similar operation was made using kidney cells from animals which had been hypophysectomized for 23 days, there was no significant inhibition of compensatory renal hypertrophy.5. The renal contents of adenosine-3',5'-monophosphate (cyclic AMP) and of guanosine-3',5'-monophosphate (cyclic GMP) in rats hypophysectomized for 2 days were of the same order as those in normal rats, but were markedly lower in rats hypophysectomized for 23 days.6. In contrast to what had been observed in normal rats, in hypophysectomized (2 or 23 days) rats, unilateral nephrectomy did not affect significantly the levels of cyclic nucleotides in the remaining kidney.7. Cross-circulating anephric normal rats with 2 day hypophysectomized animals resulted in an increase of cyclic GMP content in their kidneys. The cross-circulation between anephric normal rats and 23 days hypophysectomized rats had no effect on the level of renal cyclic GMP of the latter.8. When rats hypophysectomized for either 2 or 23 days and which had been nephrectomized were cross-circulated with normal rats, there were no changes in the content of cyclic GMP in the kidneys of the latter.