Binding of 125I-insulin to the isolated glomeruli of rat kidney

To investigate a possible action of insulin on the glomerulus, the binding 125I-insulin to the isolated glomeruli prepared from rat kidney was examined. When incubated at 22 degrees C, 125I-insulin binding proceeded with time and reached a steady state at 45 min at which time nonspecific binding was less than 25% of total binding. A small fraction of 125I-insulin was degraded during incubation. This binding was specific to insulin in that it was inhibited by unlabeled porcine and beef insulins and to a lesser extent by porcine proinsulin and desalanine-desasparagine insulin, but not by glucagon, parathyroid hormone, vasopressin, calcitonin, and angiotensin II. Increasing concentrations of nonlabeled insulin displaced 125I-insulin binding in a dose-dependent fashion. Scatchard plot of the data was curvilinear consistent with either two classes of receptors with different affinities or a single class of receptors that demonstrate negative cooperativity. The addition of excess nonlabeled insulin to the glomeruli preincubated with 125I-insulin resulted in a rapid dissociation of approximately or equal to 70% of bound 125I-insulin. Insulin decreased the increments in glomerular cyclic AMP levels by epinephrine and by prostaglandin E2, but not those by histamine. These data showed the presence of specific insulin receptors in the glomeruli, and that insulin action may be, at least in part, through modulation of glomerular cyclic AMP concentrations. Such action of insulin may underlie the alteration in glomerular ultrafiltration and the glomerular ultrafiltration and the development of glomerular lesions in diabetes mellitus, a disease in which insulin deficiency or the tissue resistance to insulin exists.

Immunological evaluation of a streptococcal preparation (OK-432) in treatment of bladder carcinoma

When 21 patients with bladder cancer (transitional cell carcinoma) were given local and systemic injections of a streptococcal preparation, OK-432, tumor regression was observed in 3 cases (14.3%). The marked infiltration of lymphocytes observed on histological examination of regressed tumors suggested that a host-mediated action was involved in the antitumor effect of OK-432.

Metabolic and endocrine alterations in end-stage renal failure

Many alterations in metabolic and endocrine function occur in end-stage renal disease. Glucose intolerance is almost always present with uremia; it improves shortly after institution of regular hemodialysis. Hyperlipidemia (type IV) is prevalent, and atherosclerotic cardiovascular disease causes death in about 50% of patients receiving long-term hemodialysis. Although plasma levels of growth hormone usually are elevated, children with chronic renal failure show growth retardation. The occurrence of thyroid disorders is difficult to determine, since many clinical features of uremia are similar to those of hyperthyroidism and hypothyroidism. The incidence of duodenal ulcer is high, possibly due to high gastrin levels. Sex hormone disturbances are common. Anemia is a constant feature of chronic renal failure; patients usually tolerate it well.

Lack of effect of hypomagnesemia on elevated plasma 1,25-dihydroxycholecalciferol in acutely phosphate-deprived rats

The effect of hypomagnesemia occurring in phosphate deprivation on elevated levels of plasma 1,25-dihydroxycholecalciferol (1,25(OH)2D3) was evaluated in rats. Phosphate deprivation was associated with an elevated plasma 1,25(OH)2D3, hypophosphatemia, and hypomagnesemia. With oral magnesium supplement during phosphate deprivation, plasma magnesium did not fall, but plasma inorganic phosphate fell and 1,25(OH)2D3 rose to comparable levels seen in phosphate-deprived rats lacking magnesium supplement. These results indicate that a rise in plasma 1,25(OH)2D3 during phosphate deprivation is not due to concomitant hypomagnesemia and support the postulate that phosphate deprivation per se is responsible for the elevated plasma 1,25(OH)2D3.

Effects of glucocorticoid deficiency on renal medullary cyclic adenosine monophosphate of rats

1. The effects of adrenalectomy on the adenylate cyclase--adenosine 3':5'-cyclic monophosphate (cyclic AMP) system of rat renal medulla were examined to evaluate the mechanism of the impaired water diuresis in glucocorticoid deficiency. 2. Concentrations of cyclic AMP in medullary tubules from adrenalectomized rats were significantly higher than in the tubules from control animals both in the presence and absence of antidiuretic hormone. 3. This abnormality was corrected by the treatment in vivo of the adrenalectomized rats with dexamethasone, but addition of this drug to the incubation medium did not abolish the differences in cyclic AMP between tubules from adrenalectomized and normal rats. 4. The activity of adenylate cyclase or cyclic AMP phosphodiesterase in vitro was not affected by adrenalectomy. 5. In glucocorticoid deficiency, the concentration of cyclic AMP in medullary tubules is increased both with and without antidiuretic hormone. This abnormality may render medullary tubules more permeable to water and may underlie the impaired water diuresis in glucocorticoid deficiency.

Effect of phosphate depletion on magnesium homeostasis in rats

The effects of phosphate depletion on magnesium (Mg) homeostasis were evaluated in rats fed a diet containing 0.03% phosphorus for periods up to 8 wk. Plasma phosphorus fell significantly (P < 0.01) from 10.1+/-0.27 (SE) to 5.0+/-0.54 mg/100 ml within 1 day and continued to fall gradually to a level of 1.2+/-0.21 mg/100 ml by the end of the 8th wk. A significant (P < 0.01) increment in urinary Mg excretion (UMgV) from 46+/-2.7 to 126+/-24 mueq/24 h occurred during the 1st day of phosphate depletion; UMgV reached a peak of 300+/-24 mueq/24 h by the 3rd day and remained high ranging between 150-300 mueq/24 h, thereafter. The magnitude of the magnesuria was related to the degree of hypophosphatemia and was not affected by lowering the calcium intake and reducing the hypercalciuria. The concentration of plasma Mg fell significantly (P < 0.01) from 1.2+/-0.02 to 0.79+/-0.10 meq/liter by the 1st day of the study and remained low throughout.Mg balance became negative during the 1st day of phosphate depletion and remained so during the entire study. This occurred despite a significant increment in the fraction of ingested Mg absorbed which became evident by the 3rd wk of phosphate depletion. Mg content of muscle, kidney, and liver were not affected but bone Mg was reduced significantly. The change in bone Mg was not due to an overall reduction in bone mineral content because bone calcium content was not affected. Supplementation of large amounts of Mg (800-1,000 mueq/day) in the drinking water produced a normalization of serum Mg but did not bring about restoration of bone Mg despite a positive Mg balance. The disturbances in Mg metabolism were independent of the age or weight of the animals. Our results indicate that phosphate depletion is associated with (a) magnesuria due to a decrease in the net renal tubular reabsorption of Mg with the main source of the urinary losses being bone Mg; (b) hypomagnesemia secondary to the renal leak of Mg; (c) negative Mg balance; and (d) increase in the intestinal fractional absorption of Mg. The latter was not adequate to compensate for the urinary losses of Mg.

Blood levels of 25-hydroxyvitamin D in nephrotic syndrome. Studies in 26 patients

The blood levels of 25-hydroxyvitamin D (25-HCC) in 26 patients with nephrotic syndrome (proteinuria of 6.5 g/24 h +/- 0.8 SEM) ranged between 1 and 18.6 ng/ml (8.6 +/- 1.0 SEM). This value was significantly lower (P less than 0.01) than that in normal subjects (21.8 +/- 2.3 ng/ml) and patients with chronic renal failure (24.8 +/- 2.3 ng/ml). There was inverse correlation (P less than 0.01) between levels of 25-HCC and magnitude of proteinuria and a direct relation (P less than 0.01) with serum albumin. Reduction in proteinuria was rapidly followed by a rise in blood 25-HCC toward normal. Ionized calcium levels were low in 16 of 26 nephrotic patients irrespective of degree of renal failure. In four of seven nephrotic patients with normal renal function, ionized calcium levels were low and showed an inverse relation with levels of parathyroid hormone. These data show that patients with nephrotic syndrome have low blood levels of 25-HCC probably due to its loss in urine. This derangement is probably responsible for the disorders of calcium metabolism in nephrosis.

Role of cyclic AMP in the natriuresis of extracellular fluid volume expansion in the dog

1. The effect of extracellular volume expansion (ECVE) on renal production of cyclic AMP was evaluated in 19 thyroparathyroidectomized dogs. ECVE was produced by the infusion of Ringer bicarbonate solution at a rate of 2 ml min-1 kg-1 body weight; cyclic AMP was measured in plasma obtained from the aorta and renal vein and in the urine. 2. During the natriuresis of ECVE urinary excretion of cyclic AMP, the clearance of cyclic AMP, net nephrogenous cyclic AMP added both to urine and to the renal vein and hence total nephrogenous cyclic AMP increased significantly. 3. This rise in net production of cyclic AMP and a significant natriuresis by the kidney persisted for 60--90 min after discontinuation of active ECVE and return of renal plasma flow to normal. 4. The results support the notion that an increase in the production of cyclic AMP by the kidney may play a role in the natriuresis of ECVE.

Renal cell metabolism in phosphate depletion: adenine nucleotide metabolism and gluconeogenesis

Effects of phosphate depletion (PD) in young rats on inorganic phosphate (Pi) and adenine nucleotide metabolism in kidney were examined to evaluate the role of altered adenine nucleotide metabolism in the pathogenesis of renal dysfunctions in PD. Despite a rapid fall in plasma pi, renal Pi and ATP levels did not fall until 2nd and 4th week, respectively. Concomitant with a fall in ATP, the equilibrium constant (Keq) of adenylate kinase decreased, suggesting an altered intracellular Mg ion concentration. The oral Mg supplement prevented a fall in plasma Mg occurring in PD as well as a fall in Keq of adenylate kinase without any effect on a decrease in tissue Pi and ATP. These data indicate that tissue levels of Pi and ATP did not fall until severe PF develops, and a concomitant Mg deficiency may play some role in the pathogenesis of some of the cellular dysfunctions seen in PD. Renal gluconeogenesis was inhibited in renal cortical tubules as early as on the 3rd day of PD. Although the mechanisms for such inhibition of gluconeogenesis are not known, this abnormal cell metabolism may underlie some of the tubular dysfunctions in PD.

Biological and immunological properties of tritiated salmon calcitonin

Tritiated salmon calcitonin was prepared by methylation of the free amino groups using tritiated sodium borohydride as precursor. Specific radioactivity was measured in competitive inhibition studies with specific anticalcitonin antibodies or tubular membranes as binding sites for calcitonin. The value observed, approx. 4 Ci/mmol, corresponded to methylation of one third of the available N-H bonds. Tritiated calcitonin prepared in this way retained full biological activity as assessed in vitro by stimulation of adenylate cyclase and in vivo by rat bioassay. Tritiated calcitonin specifically bound to isolated renal cells and nonspecific binding did not exceed 10% of total binding. Equilibrium was obtained after 15 min incubation. The hormone-receptor complex could be dissociated in the presence of an excess of unlabelled calcitonin. This data shows that tritiated calcitonin can be used in metabolic and receptor studies.

Acute actions of 1,25-dihydroxy-vitamin D3 in normal man: effect on calcium and parathyroid status

The present study was undertaken to evaluate the acute effect of 1,25-dihydroxy-vitamin D3 (1,25 (OH)2D3) on serum Ca, P and immunoreactive parathyroid (iPTH) and urinary Ca, P. and cyclic AMP. In 8 normal subjects, samples were collected over intervals of 30 to 60 min during a control day and on a treatment day following oral ingestion of 1,25(OH)2D3, 2.7 microgram. For the entire group there were no significant changes in serum Ca. P, iPTH or urinary P. Urinary Ca increased significantly 7 h after administration of 1,25(OH)2D3, and urinary cAMP decreased at 12 h. In 4 patients (group A). showing an increase in serum Ca by 0;2 to 0.4 mg/dl, serum iPTH decreased in 3, and the decrease in urinary cAMP appeared sooner. Among 4 patients showing no change in serum Ca after 1,25(HO)2D3 (group B), 3 showed an increase in iPTH. These data document the early onset of action of 1,25(OH)2D3 following its administration to normal man; increments in urinary Ca provide the most sensitive index of its action. The data provide no support for the view that 1,25(OH)2D3 exerts any direct inhibitory effect on the secretion of parathyroid hormone.

Hyponatremia and hypernatremia

The concentration of serum sodium is determined by the external balance of water. Hyponatremia occurs when total body water is in excess of sodium, and hypernatremia develops when body water is relatively decreased in relation to sodium. Both disorders may be present in patients with various disease states in which total body sodium is either decreased, normal or increased. The symptomatology in both disorders is related to the disturbance in central nervous system due to brain edema in patients with hyponatremia and brain dehydration, and cerebrovascular hemorrhages in patients with hypernatremia. The treatment of hypo and hypernatremia is achieved by correcting the abnormalities in body water content.

Interaction between parathyroid hormone and catecholamines on renal cortical cyclic AMP

Parathyroid hormone (PTH) and catecholamines (CA) increased cAMP levels in isolated tubules of rat renal cortex. A rise in cAMP could be detected 10 sec after the addition of agonists, and it reached the peak in 30-60 sec and then decreased despite the presence of active agonists. Direct relationships exist between theophylline concentrations and cAMP levels in response to agonists. Three- to fivefold rises in cAMP levels were observed with a maximal dose of PTH compared with that of CA, and there was no additive effect. Both PTH and CA stimulated renal gluconeogenesis; when added together with each maximal dose, no additive effect was observed. These results suggest the important role of phosphodiesterase to control tubular cAMP in response to hormonal stimuli, and there is a tubule cell group responding to both PTH and CA.

Watertight closure of spinal dura mater. Technical note

✓ The authors describe a technique by which a plug of fat is used to repair small rents in the spinal dura mater.

Skeletal resistance to endogenous parathyroid hormone in pateints with early renal failure. A possible cause for secondary hyperparathyroidism

Studies were carried out to evaluate whether skeletal resistance to acute increments in endogenous parathyroid hormone exists in patients with mild to moderate renal insufficiency. Hypocalcemia was induced with the infusion of ethyl-enediamine-tetra-acetate (EDTA) in 10 normal subjects and 13 patients with mild renal failure. After the induction of hypocalcemia, the concentration of serum calcium increased gradually and reached preinfusion levels by 22 h in the normal subjects; in contrast, the levels of serum calcium in patients with mild renal insufficiency were significantly lower than the preinfusion values even at the end of 26 h following the EDTA infusion. This delayed recovery occurred despite significantly higher levels of serum immunoreactive parathyroid hormone (IPTH) in the patients than in the normal subjects. The increase in the levels of IPTH reflect elevations in the concentrations of biologically active hormone since urinary cyclic AMP increased significantly. Urinary calcium excretion following the EDTA infusion was not different in both groups and, therefore, could not account for the delayed recovery of serum calcium values in the patients with renal insufficiency. These results indicate that secondary hyperparathyroidism exists early in patients with renal failure and such patients have exaggerated parathyroid hormone secretion in response to acute hypocalcemia. The data are consistent with the concept that skeletal resistance to increments in endogenous parathyroid hormone is present in such patients. This abnormality is, at least partly, responsible for the hypocalcemia and secondary hyperparathyroidism of renal insufficiency.

Renal action of cholera toxin: II. Effects on adenylate cyclase-cyclic AMP system

The effects of cholera toxin (CT) on the adenylate cyclase-adenosine 3',5'-cyclic monophosphate (cAMP) system(s) in renal cortex were examined using the isolated renal cortical tubules of rat. Unlike parathyroid hormone, catecholamines or prostaglandins, CT had no immediate effects on cAMP production by the tubules or on adenylate cyclase activity. However, after 30 min of incubation at 37 C, cAMP production by the tubules started to rise and reached a plateau between 60 and 90 min. This rise in cAMP production was not abolished by protein synthesis inhibitors (actinomycin D and cycloheximide) nor by the inhibitors of prostaglandin synthesis (acetyl-salicylate and indomethacin). Repeated washings of the tubules exposed to the toxin for five minutes at 0 or 37 C did not abolish the effect of CT to stimulate cAMP production. Assays of adenylate cyclase activity using homogenates prepared from isolated tubules which were incubated for 60 min with CT revealed an increase in the basal adenylate cyclase activity without any change in NaF-sensitive enzyme activity. It is concluded that CT binds to renal tubule cells rapidly, possibly through energy-independent process. CT stimulates adenylate cyclase activity and increases cAMP production by the renal tubule cells after a latent period of 30 min. The stimulatory effects of CT are not due to new protein synthesis or prostaglandin formation.

Renal action of cholera toxin: I. Effects on urinary excretion of electrolytes and cyclic AMP

The infusion of cholera toxin (CT), 4 mug/min, into one renal artery of normal and thyroparathyroidectomized (T-PTX) dogs produced ipsilateral increments in the excretion of Na, K, Ca, Mg and Cl. Phosphate excretion increased from both kidneys, but more from the infused kidney in intact dogs. Unilateral phosphaturia occurred in T-PTX dogs studied five or more days after T-PTX. The changes in electrolyte excretion appeared 40 to 80 min after initiation of CT infusion and the maximal effects were noted after 100 to 140 min. The effects of CT on electrolyte excretion could not be accounted for by changes in glomerular filtration rate or renal plasma flow. Urinary cyclic adenosine monophosphate (AMP) increased from both kidneys but slightly more from the infused kidney. Adenylate cyclase activity of cortex and outer medulla of the infused kidney was 109 to 142% higher than that of the control kidney. The results indicate that CT decreases the net transport of various electrolytes by the renal tubule. This effect is probably mediated by the activation of renal adenylate cyclase(s) sensitive to the enterotoxin.

Relationship between the kidney and parathyroid hormone

This report reviews the interrelationship between the activity of the parathyroid glands and renal function. Among the topics discussed are: effects of parathyroid hormone on various aspects of renal function such as: (1) glomerular filtration rate and renal blood flow; (2) renal handling of phosphorus, calcium, magnesium, sodium and potassium; (3) renal production of 1,25-dihydroxycholecalciferol; (4) renal handling of bicarbonate and acid-base metabolism, and (5) mechanism of action of parathyroid hormone on the renal cell. Further topics include: renal metabolism of parathyroid hormone; the kidney in hyperparathyroidism, and effects of renal failure on structure and function of the parathyroid glands.

Evidence for stimulation of renal gluconeogenesis by catecholamines

Isoproterenol and norepinephrine (10(-4) M) significantly increased cyclic AMP formation and glucose production by the isolated tubules of the renal cortex of the rat. These effects were abolished by propranolol. Theophylline diminished the effects of the catecholamines on gluconeogenesis despite a marked augmentation in cyclic AMP concentration. In the absence of calcium ion in the incubation medium, isoproterenol stimulates cyclic AMP production, but has no effect on gluconeogenesis. It is concluded that catecholamines enhance gluconeogenesis in renal cortical tubules by the stimulation of beta adrenergic receptors. This effect is probably mediated through adenyl cyclase-cyclic AMP system and requires an adequate level of ATP and the presence of calcium ion.