Influence of Na+ intake on dopamine-induced inhibition of renal cortical Na(+)-K(+)-ATPase

The enzyme L-amino acid decarboxylase (L-AADC), found in abundance in rat proximal tubule cell cytosol, converts L-dopa to dopamine. Dopamine, in turn, suppresses proximal tubule sodium transport by inhibiting Na(+)-K(+)-ATPase activity. We sought to determine whether changes in dietary sodium intake in rats lead to adaptation of dopamine formation and dopamine-induced Na(+)-K(+)-ATPase inhibition. In rats on a high-salt (HS) diet, the maximal velocity (Vmax) of renal cortical L-AADC was 78 +/- 19% higher than that in rats on a low-salt (LS) diet. The Michaelis constant (Km) of the enzyme remained unchanged. In renal cortical tubule cell suspensions the L-dopa-induced inhibition of ouabain-sensitive oxygen consumption (QO2) was significantly greater in rats on HS diet than in rats on LS diet. Furthermore, L-dopa completely inhibited the nystatin-induced rise in QO2 in the HS but not in the LS group. Carbidopa, an inhibitor of L-AADC, abolished the L-dopa-induced inhibition of nystatin-stimulated QO2 in cells from HS rats and was without significant effect in cells from LS rats. L-Dopa-stimulated K+ efflux was greater in cells from HS rats at 28 +/- 1 nmol.min-1.mg protein-1, compared with 7 +/- 6 nmol.min-1.ng protein-1 in cells from LS rats. By contrast, ouabain-stimulated K+ efflux did not differ between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopamine- and cAMP-regulated phosphoprotein (DARPP-32) and dopamine DA1 agonist-sensitive Na+,K+-ATPase in renal tubule cells

The cellular localization of DARPP-32, a dopamine- and cAMP-regulated phosphoprotein of Mr 32,000 that appears to mediate certain actions of dopamine in the mammalian brain by acting as an inhibitor of protein phosphatase 1, was studied in the kidney of several species. DARPP-32 mRNA and DARPP-32-like immunoreactivity were found in the cytoplasm of cells in the thick ascending limb of the loop of Henle. The specific dopamine DA1 agonist SKF 82526 caused a dose-dependent inhibition of Na+,K+-ATPase activity, which could be blocked by SCH 23390, a specific DA1 antagonist, and by PKI-(5-24) amide, a specific inhibitor of cAMP-dependent protein kinase. The results indicate that DA1 dopamine receptors and DARPP-32, an intracellular third messenger for dopamine, are part of the signal-transduction process for dopamine acting on renal tubule cells.

Paralytic ileus, a serious complication in acute diarrhoea disease among infants in developing countries

Intestinal hypomotility is a common late complication in infants with acute diarrhoeal disease in pakistan. Among the infants admitted to our gastrointestinal unit with a history of acute diarrhoea, 35% developed abdominal distension and 12% developed the full clinical picture of paralytic ileus. The infants with ileus were treated with decompression and total parenteral nutrition; in this group the mortality rate was 25%. We compared 30 infants who developed ileus (group A) with an age-matched control group of infants (group B) who were admitted because of acute diarrhoea but did not develope ileus. The use of antimotility drugs was significantly more frequent in group A. Serum-K was not different in in group A (3.92 +/- 0.22 mmol/l) and group B (4.32 +/- 0.18 mmol/1). However, there were more patients who had serum-K below 3 mmol/l in group A (8/30) than in group B (5/30). We conclude that the use of antimotility drugs predisposes to the development of ileus in infants with acute diarrhoea. Hypokalemia may contribute to ileus in a few cases but is generally not a prerequisite.

Glomerular adaptation in uninephrectomized young rats

To study the glomerular adaptation during compensatory renal growth starting in infancy, we assessed afferent effective ultrafiltration pressure (PUF), glomerular filtration area and hydraulic conductivity in rats uninephrectomized (Nx) or sham-operated (S) at 5 days of age. Rats were fed a normal protein diet and studied at 20 and 60 days of age. Single nephron glomerular filtration rate was significantly higher in Nx than in S rats both at 20 days of age (mean +/- SEM: 15.0 +/- 1.5 vs 7.4 +/- 0.7 nl/min) and 60 days of age (80.7 +/- 4.6 vs 43.5 +/- 3.2 nl/min). Afferent effective PUF, estimated by the stop-flow method, was significantly higher in Nx than in S rats both at 20 days (22.5 +/- 0.8 vs 18.3 +/- 0.4 mmHg) and 60 days (28.3 +/- 1.0 vs 23.2 +/- 1.1 mmHg). The filtering area per glomerulus, calculated as the area of the glomerular basement membrane facing both the endothelial and the epithelial cells, but not the mesangial cells, was not different in Nx and in S rats at 20 days (3.0 +/- 0.3 vs 2.8 +/- 0.1 10(4) microns 2), but it was significantly greater in Nx than in S rats at 60 days (23.3 +/- 3.7 vs 9.9 +/- 0.9 10(4) microns 2). The hydraulic conductivity determined in isolated glomeruli was similar in Nx and in S rats at 20 days of age (1.40 +/- 0.11 vs 1.69 +/- 0.23 microliters/min.mmHg.cm2) but was significantly decreased in 60-day-old Nx rats, compared with S rats of the same age (1.52 +/- 0.11 vs 2.35 +/- 0.17 microliters/min.mmHg.cm2).(ABSTRACT TRUNCATED AT 250 WORDS)

Renal function in different forms of renovascular hypertension in rats

This study examines renal function in different rat models of renovascular hypertension. Hypertension was induced by constriction of the aorta proximal to the renal artery (PAC), by PAC and nephrectomy (PAC + Nx) or by renal artery stenosis (RAS). PAC + Nx is equivalent to the Goldblatt 1 kidney-I clip hypertension model. The PAC rats were studied 3 weeks after surgery. Hypertension was by then well established. GFR, measured as the clearance of inulin, was significantly lower in PAC rats than in control (C) rats. GFR was the same in PAC + Nx rats as in C rats, but significantly lower in PAC + Nx than in Nx rats. Kidney weight was significantly higher in PAC + Nx rats than in C rats. Filtration fraction (FF), measured as the ratio between GFR and the clearance of PAH, was significantly higher in PAC and PAC + Nx rats than in C and Nx rats. In RAS rats hypertension was not established until 6 weeks after surgery, and RAS is equivalent to Goldblatt 2 kidney-I clip hypertension. Renal artery constriction was moderate as judged from the weight ratio between the stenosed and contralateral kidneys. The GFR in the stenosed kidney was not significantly lower in the contralateral kidney. FF was significantly higher in RAS rats than in C rats in both the stenosed and the contralateral kidneys, but the increase was less pronounced than in PAC and PAC + Nx rats.

Studies of terminal differentiation of electrolyte transport in the renal proximal tubule using short-term primary cultures

There are several lines of indirect evidence suggesting that the renal tubule cells have not yet reached terminal differentiation at birth. Methods used in cell biology can now be applied to study renal ontogeny. This review describes how primary cultures of proximal tubule cells from rats can be used to investigate developmental changes in Na permeability and Na-K-ATPase-mediated transport.

Na,K-ATPase activity in renal tubule cells from Milan hypertensive rats

Several abnormalities of cation transport have been described in the Milan hypertensive rats (MHS). In this study we examined Na,K-ATPase activity in proximal convoluted tubules (PCT) cells and medullary thick ascending limb of Henle cells (TAL) from MHS and from the Milan normotensive rats (MNS). Na,K-ATPase activity was determined as 32P-ATP hydrolysis in single tubule segments. Na,K-ATPase activity (pmol Pi/mm t/h) was significantly higher in MHS than MNS both in PCT (903 +/- 227 n = 8 v 506 +/- 285 n = 12) and TAL (4324 +/- 800 n = 5 v 3063 +/- 625 n = 5). Na,K-ATPase dependent respiration was determined in PCT cell from MNS and MHS. Under basal condition Na,K-ATPase dependent respiration (mumol O2/mg protein/h) was higher in MHS than in MNS (24.2 +/- 1.8 n = 5 v 16.1 +/- 0.4 n = 5). When the cells were Na loaded by amphotericin Na,K-ATPase dependent respiration increased significantly more in MHS than MNS (38.4 +/- 1.6 v 26.8 +/- 2.2 n = 4). Thus, Na,K-ATPase activity is higher in renal tubule cells both at normal intracellular Na and after the cells have been Na loaded. The results indicate that regulation of Na homeostasis in renal tubule cell is different in MHS and MNS.

Influence of vesicoureteral reflux and urinary tract infection on renal growth in children with upper urinary tract duplication

The growth of the renal parenchyma was examined in children with duplicated outflow systems, vesicoureteral reflux (VUR), urinary tract infection (UTI) and no sign of obstruction. Ten patients with reflux occurring only in the caudal system (group A) and 4 patients with reflux both to the caudal and the apical system (group B) were studied shortly after their first UTI (study 1) and then 1.5 to 9 years later (study 2). The frequency of UTI was relatively high during the follow-up period. At urography, renal length and renal area were normal in group A in studies 1 and 2. Parenchymal thickness of the apical pole (APT/L) did not differ from normal values in any of the studies. Parenchymal thickness of the caudal pole (CPT/L) was significantly smaller than normal in both studies. There was also a significant decrease in CPT/L between study 1 and 2. UTI during the first year of life was associated with a greater reduction in CPT/L. The determination of renal length and renal area in children with a duplicated ureter, VUR and UTI, does not identify subjects at risk of developing renal growth retardation while serial determinations of parenchymal thickness appear to be an appropriate method.

Ascending pyelonephritis in young rats retards kidney growth

Several radiological studies have suggested that pyelonephritis in infancy and childhood may result in kidney growth retardation without renal scarring. In the present study, we induced ascending pyelonephritis in 20-day-old rats with intravesical infusion of E. coli. Four days after infusion, E. coli was cultured from all renal cortex. The rats were either left untreated (PNu) or were treated with trimethoprim-sulfa (PNt). The rats were investigated one month after infection and compared with an age-matched control group (C). Seventy-nine percent of the PNu rats had recovered spontaneously from infection. Body weight was the same in all groups. In PNu rats, kidney weight (KW), kidney area (KA) and glomerular filtration rate (GFR) were significantly decreased. KW, KA and GFR were similar in PNt and C rats. The numbers of filtering nephrons were not reduced by the infection. The total cortical DNA content (index of cell number) was significantly lower in PNu (5.30 +/- 0.32 mg) and PNt (6.62 +/- 0.44 mg) than in C rats (8.48 +/- 0.49 mg). The cortical DNA content was significantly lower in PNu than in PNt rats. The cortical protein/DNA ratio was significantly higher in PNu rats than in C rats. The protein/DNA ratio was similar in PNt and PNu rats. The increase in protein/DNA ratio was interpreted as a sign of cell hypertrophy. The inflammatory process as such did not increase the protein/DNA ratio. The kidneys were also examined for structural lesions. Signs of scarring, inflammation and cell necrosis were almost absent in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Na+-K+-ATPase is an effector protein for protein kinase C in renal proximal tubule cells

Activators of protein kinase C (PKC) inhibit sodium transport in proximal tubules (PT) (M. Baum and S. R. Hays. Am. J. Physiol. 254 (Renal Fluid Electrolyte Physiol. 23): F9-F14, 1988. In this study we have evaluated the effect of PKC activators on the enzyme responsible for active sodium transport, Na+-K+-ATPase. Both endogenous (diacylglycerol, DAG) and exogenous (phorbol esters, PE) activators were used. Enzyme activity was determined in permeabilized single PT segments. In vehicle-incubated PT, Na+-K+-ATPase activity (pmol Pi.mm tubule-1.-1 h) was 1,403 +/- 128. The synthetic DAG, L-alpha-l-oleoyl-2-acetoyl-sn-3-glycerol (10(-4) M) significantly inhibited Na+-K+-ATPase activity to 673 +/- 51, P less than 0.05. The PE-phorbol 12,13-dibutyrate (PDBu), induced a time- and dose-dependent inhibition of Na+-K+-ATPase activity. Inhibition was significant at 15 and maximal at 20 min. Na+-K+-ATPase activity in PT incubated with PDBu was 796 +/- 171 (10(-8) M), 570 +/- 198 (10(-7) M), and 484 +/- 130 (10(-6) M). A PE that does not activate PKC, 4-alpha-phorbol didecanoate, did not inhibit Na+-K+-ATPase activity. PDBu 10(-7) M had no effect on purified Na+-K+-ATPase. Sphingosine (SP), a PKC inhibitor, abolished the inhibitory effect of PDBu (10(-7) M) on Na+-K+-ATPase activity. Dopamine (DA) is a physiological inhibitor of Na+-K+-ATPase activity in PT [A. Bertorello, T. Hökfelt, M. Goldstein, and A. Aperia Am. J. Physiol. 254(Renal Fluid Electrolyte Physiol. 23): F795-F801, 1988].(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of Na+-K+-ATPase activity in kidney proximal tubules: involvement of GTP binding proteins

This study evaluates the involvement of GTP-dependent regulatory proteins (G-proteins) in the regulation of Na+-K+-ATPase activity in proximal convoluted tubule (PCT) segments. Single PCT segments were dissected from rat kidney and permeabilized to allow nucleotides and medium free access to the interior of the cell. A GDP analogue that blocks GTP-dependent activation of the G-protein, GDP beta S (400 microM) significantly inhibited PCT Na+-K+-ATPase activity when Na in the medium (Nam) was greater than or equal to 70 mM. The inhibition was attenuated when Nam was 55 and 35 mM and was no longer significant when Nam was 25 mM. GDP beta S had no inhibitory effect on the activity of purified Na+-K+-ATPase. A nonhydrolyzable GTP analogue, GppNHp (50 microM) significantly increased Na+-K+-ATPase activity when Nam was 25 and 35 mM, but not when Nam was 55-140 mM. Dopamine (DA) and DA1 plus DA2 agonists significantly inhibit Na+-K+-ATPase activity. DA inhibition was competitively abolished by GppNHp. In PCT segments from rats pretreated with pertussis toxin, DA and DA1 plus DA2 agonist inhibition of Na+-K+-ATPase activity was abolished. In PCT segments from rats pretreated with cholera toxin, basal Na+-K+-ATPase activity was increased, but DA significantly inhibited Na+-K+-ATPase activity. Na+-K+-ATPase activity in PCT segments is regulated via a G-protein that stimulates Na+-K+-ATPase activity and a DA-activated pertussis toxin-sensitive G-protein that inhibits Na+-K+-ATPase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of protein intake decreases glomerular filtration rate in young type 1 (insulin-dependent) diabetic patients mainly in hyperfiltering patients

The influence of different protein intake on renal function was studied in 16 Type 1 (insulin-dependent) diabetic patients, aged 15-23 years, with onset of diabetes before puberty and with a duration of diabetes between 5 and 20 years. The glomerular filtration rate, renal plasma flow, albumin excretion rate, and blood pressure were examined in a cross-over randomised order after 10 days on isocaloric diets with either 10% (i.e. 0.9 +/- 0.06 g.kg-1.day-1) or 20% (1.9 +/- 0.1 g.kg-1.day-1) of the calories as protein, the latter being equal to the recommended diet. Dietary compliance was evaluated using fractional phosphate excretion and overnight urea excretion. Glomerular filtration rate was lower after the low-protein diet compared to the usual protein diet (p less than 0.001). Patients with glomerular filtration rate above +2 SD of the normal mean on the usual protein diet (n = 6) exhibited the steepest fall in glomerular filtration rate with a mean decrease of 20 ml/min compared to 7 ml/min in those with initially normal glomerular filtration (p = 0.01). Filtration fraction tended to decrease on low protein diet, more so in initially hyperfiltering patients (p = 0.09). Renal plasma flow remained unchanged. In patients with elevated glomerular filtration rate on usual protein diet, albumin excretion rate and systolic, but not diastolic blood pressure, were decreased on low protein diet (p = 0.03 and p = 0.01, respectively) but not in initially normal-filtering patients. Mean blood glucose and serum fructosamine were unchanged on both diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Locally formed dopamine inhibits Na+-K+-ATPase activity in rat renal cortical tubule cells

Dopamine, generated locally from L-dopa, inhibits Na+-K+-ATPase in permeabilized rat proximal tubules under maximum transport rate conditions for sodium. To determine whether locally formed dopamine inhibits Na+-K+-ATPase activity in intact cortical tubule cells we studied the effect of L-dopa on ouabain-sensitive oxygen consumption rate (QO2) and 86Rb uptake in renal cortical tubule cell suspensions. L-Dopa (10(-4) M) did not affect ouabain-insensitive QO2 or mitochondrial respiration. However, L-dopa inhibited ouabain-sensitive QO2 in a concentration-dependent manner, with half-maximal inhibition (K0.5) of 5 x 10(-7) M and a maximal inhibition of 14.1 +/- 1.5% at 10(-4) M (P less than 0.05). L-Dopa also blunted the nystatin-stimulated QO2 in a concentration-dependent manner, with a K0.5 of 5 x 10(-8) M and a maximal inhibition of 21.8 +/- 1.2% at 10(-5) M (P less than 0.05), indicating that L-dopa directly inhibits Na+-K+-ATPase activity and not sodium entry. Ouabain-sensitive 86Rb uptake was also inhibited by L-dopa (16.0 +/- 2.4%, P less than 0.05). Carbidopa (10(-4) M), an inhibitor of the conversion of L-dopa to dopamine, eliminated the effect of L-dopa on ouabain-sensitive QO2 and 86Rb uptake, indicating that dopamine rather than L-dopa was the active agent. The finding that the L-dopa concentration-response curve was shifted to the left by one order of magnitude in the presence of nystatin suggests that the inhibitory effect is enhanced when the intracellular sodium concentration is increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Differentiation of Na+-K+ pump in rat proximal tubule is modulated by Na+-H+ exchanger

This study examines the effect of in vivo modulation of Na+-H+ exchange activity on the development of Na+-K+-ATPase in rat kidney proximal convoluted tubule (PCT) segments. To stimulate Na+-H+ exchanger (major entry pathway for Na in PCT), weanling rats were fed NH4Cl for 4 days to induce metabolic acidosis (MA). In vehicle (Vh)-fed rats PCT Na+-K+-ATPase activity (pmol Pi.mm tubule-1.h-1 +/- SE) increased from 481 +/- 78 at 16 days to 1,122 +/- 119 at 20 days. In 20-day-old chronic MA rats, PCT Na+-K+-ATPase activity was 1,717 +/- 109, i.e., significantly higher (P less than 0.01) relative to controls. Chronic MA had no effect on PCT Mg ATPase activity and on Na+-K+-ATPase in the medullary thick ascending limb (MTAL). To inhibit the Na+-H+ exchanger, weanling rats received amiloride (30 micrograms.100 g body wt-1.day-1) via osmotic minipump for 4 days. In Vh-treated rats PCT Na+-K+-ATPase increased from 481 +/- 78 at 16 days to 1,428 +/- 81 at 20 days. In rats given chronic amiloride, PCT Na+-K+-ATPase was significantly lower (858 +/- 75) at 20 days relative to controls but PCT Mg ATPase and MTAL Na+-K+-ATPase activity was the same as in controls. Chronic MA and amiloride had no significant effect on PCT Na+-K+-ATPase activity in adult rats. Acute MA and acute amiloride injection had no significant effect on PCT Na+-K+-ATPase in weanling rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of low-dose dopamine infusion on urinary prostaglandin E2 excretion in sick, preterm infants

In pharmacological doses dopamine (DA) will interact with several endocrine systems and both inhibit (prolactin, thyrotropin) and enhance (renin, angiotensin) hormonal release. In this study we have examined whether DA given to preterm neonates will influence prostaglandin (PG) production. The question is of importance since vasodilator PGs play a role in postnatal adaptation. We determined the effect of low dose DA infusion on the 24 h urinary PGE2 excretion rate (an index of renal PGE2 synthesis) in preterm infants. Six preterm neonates, with a 24-h requirement of 2 micrograms/kg per min DA treatment for oedema, moderate oliguria, poor peripheral perfusion and/or mild systemic hypotension were studied on days 2 (Day 1), 3 (Day 2, the day of DA infusion), and 4 (Day 3, DA discontinued) of life. Six preterm infants (control group) that did not require DA infusion were also studied to monitor possible spontaneous changes in the renal PGE2 production on days 2, 3 and 4 of life. In the control group urine output (Uv) and PGE2 excretion rate remained unchanged during the study. In the study group DA administration resulted in nearly two-fold increases in both the Uv (194%) and PGE2 excretion (182%). Urinary PGE2 excretion was, however, closely related to urine flow in both the control infants (Day 1-3) and the study group infants (Day 1-2). Since increased diuresis stimulates renal PGE2 production, our data suggest that the increased PGE2 excretion on Day 2 in the study group was not due to a direct effect of DA on PGE2 synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms for colonic sodium transport during ontogeny: loss of an amiloride-sensitive sodium pathway

Net colonic sodium and fluid absorption is higher in suckling and weanling rats than in adult rats. This study was undertaken to investigate the mechanisms behind these differences. In vivo perfusion of the colon was performed in 14- to 80-day-old rats. Net Na and water uptake decreased exponentially from 14 to 80 days of age. Na uptake was 402 +/- 73 micrograms Eq/min/g DT in 20-day-old rats and 116 +/- 6 mu Eq/min/g DT in 40-day-old rats. After amiloride treatment, net Na transport was reversed to net secretion (-79 +/- 36 mu Eq/min/g DT) in 20-day-old rats. Amiloride had no effect on the net Na transport in 40-day-old rats. cAMP stimulation significantly increased the net Na uptake in 20-day-old rats and significantly reduced the net Na uptake in 80-day-old rats. cAMP did not increase the net uptake in amiloride-treated 20-day-old rats. We conclude that there are both quantitative and regulatory changes in the pathways for colonic Na transport during development, and we speculate that the large amiloride-sensitive sodium uptake in the young colon is adaptive and contributes to the sodium accretion necessary for rapid growth during late postnatal development.

Proximal tubule Na+-K+-ATPase activity is inhibited during high-salt diet: evidence for DA-mediated effect

Locally produced dopamine (DA) causes a reversible and dose-dependent inhibition in Na+-K+-ATPase activity in rat proximal tubule (PT) segments [A. Aperia, A. Bertorello, and I. Seri. Am. J. Physiol. 252 (Renal Fluid Electrolyte Physiol. 21): F32-F45, 1987.]. To examine whether this effect might be of physiological importance, rats were given normal-salt (NS) or high-salt (HS) diet for 10 days. HS diet significantly increased Na excretion but did not alter glomerular filtration rate (GFR). Benserazide (Bz), an inhibitor of the enzyme L-aromatic amino acid decarboxylase (AADC) that converts L-dopa to DA, significantly attenuated the natriuresis in HS rats but had no effect on GFR. By use of immunofluorescence (IF) studies AADC was localized to the PT. Specific AADC IF was not observed in the medulla. In AADC-positive PT segments, Na+-K+-ATPase activity was significantly lower in HS rats than in NS rats (P less than 0.001). In AADC-negative medullary thick ascending limb, Na+-K+-ATPase activity was the same in NS and HS rats. If HS rats were given Bz just before study, PT Na+-K+-ATPase activity increased significantly and was not different from Na+-K+-ATPase activity in PT segments from NS rats. Bz had no significant effect on PT Na+-K+-ATPase activity in NS rats. In PT segments from Bz-treated rats, DA inhibited Na+-K+-ATPase activity already at a dose of 10(-8) M, whereas in segments from NS rats, significant inhibition of Na+-K+-ATPase activity was not observed until DA was increased to 10(-7) M.(ABSTRACT TRUNCATED AT 250 WORDS)

Kidney function in adults born with unilateral renal agenesis or nephrectomized in childhood

We have evaluated the long-term prognosis in an unselected group of adult patients either uni-nephrectomized in childhood because of hydronephrosis or born with unilateral renal agenesis. Thirty-six patients aged 7-47 years were followed for 7-40 years. In 23 control subjects aged 20-47 years the glomerular filtration rate (GFR) and the p-aminohippuric acid clearance (CPAH) did not change significantly with age. In patients with a single kidney the size of that kidney was larger and GFR and CPAH were higher than single kidney values in control subjects. However, in patients with a single kidney since childhood the GFR and the CPAH declined slowly but significantly during the follow-up period. Significant microalbuminuria occurred in 47% of the patients with a single kidney and was more frequent with a longer follow-up period. No patient had renal insufficiency or a marked increase in arterial blood pressure. We conclude that in patients with a single kidney since childhood the long-term prognosis is good, but the late decrease in GFR and increase in albumin excretion may indicate a moderate risk for premature renal damage.

Mitotic response to high protein intake in different renal cell types in weanling rats

We examined the effect of high protein intake on the mitotic response (3H-thymidine incorporation) in the glomerulus, proximal tubule (PT), thick ascending limb of Henle (TAL), distal tubule (DT) and collecting duct (CD) in kidneys from 16- to 24-day-old rats that received an isocaloric diet containing 21% (NP) and 50% (HP) protein from 16 days of age. Nephron filtration rate was also determined. After two days of HP diet, thymidine incorporation (TI) was significantly increased in PT and TAL. After two days on HP diet TI was most pronounced in TAL. After eight days on HP diet TI remained elevated in PT, but not in TAL. HP did not increase TI in DT or CD. The glomerular TI was the same in HP as in NP rats after two and four days on the diet, but was significantly elevated after eight days on HP diet. The nephron filtration rate was increased after two days and remained significantly elevated after eight days on HP diet. The proximal tubule fractional reabsorption was the same in 24-day-old NP and HP rats. We conclude that the results are compatible with the hypothesis that the Na load is a major factor triggering tubular growth after HP intake. Glomerular growth is secondary to increase in nephron filtration rate.

Hypocalcemia and hyperphosphatemia in severely dehydrated children with and without convulsions

Tetanic convulsions are not uncommon among severely dehydrated children in the developing countries. This raises the question whether these children have disturbances in the homeostasis of divalent ions. Serum values are reported of calcium, magnesium, phosphorus, sodium and potassium, as well as blood pH in children below 3 years of age with acute watery diarrhoea and with an estimated weight loss of about 10%. The study was performed on dehydrated children with (DC) or without (D) convulsions. Values were obtained on admission and following rehydration therapy (RT). On admission serum calcium was low in both D and DC children. Serum phosphorus was likewise elevated in both D and DC children. Serum magnesium was slightly elevated in the DC but not in the D group. No patient had hypernatremia. During RT, serum calcium increased significantly and serum phosphorus decreased significantly in D and DC children. Serum calcium showed a significant inverse correlation with serum phosphorus and a significant direct correlation with blood pH. Treatment of DC children with i.v. calcium and i.m. magnesium had no immediate effect on the convulsions. Our conclusion is that severely dehydrated children will develop hypocalcemia. The cause may be a redistribution of calcium into the cells, parallelled by a redistribution of phosphorus from the intra- to the extracellular space.