Metabolic and calcium kinetic studies in idiopathic hypercalciuria.

Calcium balances and calcium kinetic studies using (47)Ca were performed in nine male patients with idiopathic hypercalciuria and in three normal male subjects. A sharp reduction in calcium intake in eight patients with idiopathic hypercalciuria caused a decrease in urinary calcium excretion, the latter remaining elevated above that reported for normal subjects on a low calcium diet. The hypercalciuric patients had an enlarged miscible calcium pool size, an increased calcium turnover rate, increased bone formation and bone resorption rates, and an elevated true intestinal calcium absorption rate, the increase of the latter three parameters being proportional to the increase of the turnover rate. The fraction of the calcium turnover rate excreted in the urine was elevated whereas that constituted by the endogenous fecal calcium excretion was decreased. Arguments are presented for the concept that the primary abnormality in idiopathic hypercalciuria is neither renal calcium hyperexcretion nor intestinal calcium hyperreabsorption, but a more fundamental disturbance in calcium metabolism of as yet unknown cause, leading to a high calcium turnover.

The effect of beta-adrenergic blocking agents on experimental porphyria induced by 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) in vivo and in vitro.

The effect of DL-propranolol on 3',5'-diethoxycarbonyl-1,4-dihydrocollidine-induced experimental porphyria was studied. DL-Propranolol, a beta-adrenergic blocking agent with non-specific membrane effects, partially inhibited 3',5'-diethoxycarbonyl-1,4-dihydrocollidine-induced delta-aminolevulinate synthetase activity both in rats and in chick embryo liver cells in culture. In rats, DL-propranolol decreased urinary delta-aminolevulinate and porphobilinogen but no change occurred in the 24-h urinary excretion of total porphyrins and in the concentration of porphyrins in the liver. In cultured chick embryo liver cells treated with 3',5'-diethoxycarbonyl-1,4-dihydrocollidine, DL-propranolol decreased accumulation of porphyrins in the medium. D-Propranolol, oxprenolol and quinidine acted like DL-propranolol in chick embryo liver cells in culture treated with 3',5'-diethoxycarbonyl-1,4-dihydrocollidine. Pindolol, practolol and lidocaine had no effect. Phenobarbitone had a synergistic effect on the induction of delta-aminolevulinate synthetase by 3',5'-diethoxycarbonyl-1,4-dihydrocollidine in cultures of chick embryo liver cells. This induction was partially inhibited by propranolol. However, the increased accumulation of porphyrins in the medium caused by 3',5'-diethoxycarbonyl-1,4-dihydrocollidine was inhibited by the addition of phenobarbitone. This inhibited induction was further decreased by propranolol. Most of our results indicate that the drugs tested act mainly by their effects on membranes.

The effects of succinylacetone (4,6-dioxoheptanoic acid) on delta-aminolevulinate synthase activity and the content of heme in monolayers of chick embryo liver cells.

Succinylacetone was shown to inhibit aminolevulinate dehydratase (5-aminolevulinate hydro-lyase (adding 5-aminolevulinate and cyclizing), EC 4.2.1.24) to reduce cellular heme and porphyrins and to induce delta-aminolevulinate synthase (succinyl-CoA:glycine C-succinyltransferase (decarboxylating), EC 2.3.1.37) in monolayers of chick embryo liver cells. Marked synergistic effects on delta-aminolevulinate synthase activity were obtained by combining succinylacetone with levulinate and porphyrogenic drugs. The time course of delta-aminolevulinate synthase activity showed a delayed synergistic response.

L-Alanine: 4,5-dioxovalerate transaminase does not regulate heme synthesis in rat liver.

L-Alanine: 4,5-dioxovalerate transaminase (ADT) was determined in liver homogenates of rats treated by either inducers of porphyrin synthesis or the repressor, hemin. ADT activity was not induced by the porphyrinogenic agents nor reduced by hemin, indicating that ADT probably has no regulatory role in the heme synthesis pathway. The same conclusion was drawn from similar experiments performed in monolayers of chick embryo liver cells.

Prevention of hypoglycemic attacks by propranolol in a patient suffering from insulinoma.

An insulinoma was diagnosed in a fifty-seven-year-old woman suffering from frequent hypoglycemic attacks. Propranolol--a beta-adrenergic blocker--in a dose of 80 mg. per day effectively prevented recurrent hypoglycemic attacks. It also corrected the basal hyperinsulinemia as well as the increased insulin secretion which results from stimulation with glucose or arginine.

Evidence of abnormality of lymphocyte uroporphyrinogen synthase in family members of patients with lymphoproliferative diseases.

Patients with active lymphoproliferative diseases (LPD) were shown to have high activity of lymphocyte uroporphyrinogen synthase (L-UROS), the enzyme which converts porphobilinogen to uroporphyrinogen. The mean L-UROS activity of 64 first-degree relatives of patients with LPD was significantly higher than that of a control group and 45% of these relatives had pathological values of L-UROS. L-UROS activity was also determined in the spouses of 2 patients and was pathologically elevated in both. The pattern of pathological values among family members may indicate the presence of a communicable agent.

The heme biosynthetic pathway in lymphocytes of patients with malignant lymphoproliferative disorders.

The metabolism of heme is impaired in lymphocytes of patients with malignant lymphoproliferative disorders (MLPO). Two of the enzymes of the heme biosynthetic pathway, delta-aminolevulinic acid dehydrase (ALAD) (EC 4.2.1.24) and ferrochelatase (FC) (EC 4.99.1.1) are markedly reduced. The activity of porphobilinogen deaminase (PBGD) (EC 4.3.1.8) is increased. The rate-limiting enzyme of heme biosynthesis in the liver, aminolevulinate synthase (ALAS) (EC 2.3.1.37) remains unchanged although the concentration of total heme in the lymphocytes is markedly reduced. This might reflect a lack of negative feedback inhibition by heme on ALAS activity in this system.

The influence of propranolol on the concentration of heme and on the activity of delta aminolevulinate synthase in monolayers of chick embryo liver cells.

The addition of propranolol to monolayers of chick embryo liver cells caused a rapid increase in cellular heme, followed by an equally rapid decrease. Subsequently the concentration of heme rose at a relatively slower rate. About 10 hr after addition of propranolol to the medium a plateau level was reached at +/- 35% above control values. Changes in the activity of delta-aminolevulinate synthase (ALAS) were negatively correlated with those of cellular heme. Cycloheximide prevented the above phenomenon. ALAS activity was not clearly correlated with the rapid, partial inhibition of protein synthesis, caused by propranolol. These observations are related to the beneficial influence of administration of hemin or of propranolol to patients with acute attacks of hepatic porphyria.

Evidence relating the inhibitory effect of cobalt on the activity of delta-aminolevulinate synthase to the intracellular concentration of porphyrins.

This study shows that the inhibition of ALAS activity caused by cobalt is directly correlated with the intracellular porphyrin concentration, thus indicating that cobalt exerts its inhibitory effect on ALAS activity as a result of the formation of cobalt-protoporphyrin.

The effects of metalloporphyrins, porphyrins and metals on the activity of delta-aminolevulinic acid synthase in monolayers of chick embryo liver cells.

The effect of various metals, porphyrins and metalloporphyrins on the activity of delta-aminolevulinate synthase (ALAS) was measured in monolayers of chick embryo liver cells in order to determine whether the metal moiety of heme or heme itself is the regulator of ALAS activity. Iron, magnesium, zinc, copper, manganese and nickel did not decrease ALAS activity in non-induced and in cells induced by allyl-isopropylacetamide (AIA). Cobalt decreased both non-induced and induced activity. Porphyrins inhibited ALAS, apparently only after having been converted into metalloporphyrins. Almost all the metalloporphyrins examined decreased ALAS activity. None of the substances, at the concentrations used, was toxic to the cells. These observations indicate that probably heme and not iron is the regulator of ALAS activity in monolayers of chick embryo liver cells.

Antipsychotic effect of propranolol on chronic schizophrenics: study of a gradual treatment regimen.

Ten chronic treatment-resistant schizophrenic patients were treated in a single-blind trial for six weeks with propranolol in daily doses increasing up to 3 g in order to evaluate a modified dose regimen of propranolol treatment in these patients. Four of the patients improved significantly and could be released from the hospital, regaining premorbid social and work adjustments. The modified regimen proved safe as long as the dose increment was not more than 80 mg/day. The mean therapeutic level of propranolol was 1600 mg/day, which proved to be a safe dose. Although three patients with hypertensive encephalophaty responded, their response was related not to the maximum dose but to a drastic change in the rate of the dose increase. It seems that on the basis of these results a double-blind comparative study would be worthwhile.

Impairment of induction of delta-aminolevulinic acid synthase by gluconeogenic amino acids and carbohydrates in vitro.

This study was undertaken in a system of chick embryo liver cells incubated in Earle's Basal Salt Solution with hormones. Impairment of induction of delta-aminolevulinic acid synthase (ALAS) by allyl-isopropylacetamide (AIA) was observed in the presence of glucose. Fructose and various gluconeogenic substances including gluconeogenic amino acids had a similar effect. Leucine, which is purely ketogenic, did not influence induction of ALAS. SH-containing amino acids increased induction of ALAS by AIA. The glucose analogues 3-O-methylglucose and 2-deoxyglucose did not impair induction of ALAS by AIA. The inhibitory effect of glycerol, fructose, and glycine was not affected by 3-O-methylglucose but was reversed by 2-deoxyglucose. The results indicate that the salutary effects of proteins on acute attacks of hepatic porphyria are probably caused by their gluconeogenic properties and that glucose-6-phosphate, or metabolite of glucose-6-phosphate that is not in the glycolytic pathway, is the active agent that leads to the glucose-like effect.

The porphyrinogenic effect of simvastatin in experimental systems.

Attacks of acute hepatic porphyria have been previously reported to be frequently associated with transient hypercholesterolemia. This investigation was undertaken in order to establish whether the hypocholesterolemic effect of simvastatin (MK-733) is associated with inhibition of porphyrin metabolism. In two experimental models of acute hepatic porphyria--monolayers of chick embryo liver cells induced by DDC, and diethoxycarbonyl dihydrocollidine (DDC) injected rats--simvastatin was shown to increase porphyrin formation. A similar increasing effect was observed in a system which mimics the latent phase of porphyria, non-induced monolayers of chick embryo liver cells. We conclude that simvastatin is a porphyrogenic drug and should therefore be used with extreme caution in patients with hypercholesterolemia who also have latent porphyria. Its administration should be discontinued, at least temporarily, in patients with hypercholesterolemia during acute attacks of hepatic porphyria.

The possible role of beta-adrenergic and alpha-adrenergic antagonist sensitive systems in the brain in the mechanism of psychosis.

On the basis of clinical observations on psychotic patients during treatment with adrenergic blocking drugs it is postulated that normally the activities of two systems in the brain are balanced: one of these systems can be blocked by beta-adrenergic blocking drugs and the other is responsive to alpha-adrenergic blocking drugs. Psychosis may occur when either the total activity is too high or too low, or when the balance is disturbed. Specific psychiatric syndromes are outlined as related to either of these systems.

beta-adrenergic blocking drugs in psychiatry: present status, future approaches and research.

Clinical trials with propranolol were performed in 44 carefully selected psychiatric patients. Propranolol was administered in 8 equal doses over 24 hours and increased at a daily rate of 400 mg. Treatment was monitored by patient's reactions and by periodic examination of pulse rate and blood pressure. Results showed marked to moderate improvement, often within 24 to 48 hours, in two-thirds of the patients treated. Concurrent with stabilization of heart rate and blood pressure at about 60/min and 90/60 mm Hg respectively, improvement was noted in anxiety, psychomotor hyperactivity, thought process disturbance, hallucinations, and disturbances in affect. Our studies and those of other investigators indicate that propranolol and oxprenolol, and possibly other beta-adrenoceptor blocking drugs, may have a beneficial influence on psychotic syndromes. Further well-controlled clinical trials seem warranted. Indications for use, dosages, and combinations with other drugs, mainly phenothiazines, must be delineated. Laboratory investigations may add considerably in these respects ans may lead to safe treatment regimes with minimal side effects.

[Porphyria and porphyrinuria].

In latent hepatic porphyria normal porphyrins are frequently excreted, but porphyrinuria accompanies many clinical conditions not associated with porphyria. Therefore, the diagnosis of latent porphyria cannot be made by examining for urinary porphyrins alone. We use 16 laboratory methods, some of which which we developed, including sensitive HPLC separation procedures, for determining relevant enzymes, and porphyrins and their precursors in urine, feces and blood. These methods enable use to distinguish between changes in porphyrin metabolism observed in many cases of latent porphyria, as opposed to similar changes which may occur during therapy with certain drugs and in common clinical conditions. During the past 4 years we investigated 406 patients suspected of porphyria. 160 had increased excretion of porphobilinogen, and/or aminolevulinic acid, and/or porphyrins. 87 of them had porphyrinuria only. Without our clinical and laboratory experience, all would have been diagnosed as porphyria. Further examinations revealed that only 14 had porphyria, 8 of whom had porphyrinuria and 6 had normal urinary porphyrins. Overall, there have been 44 families with porphyria diagnosed in our laboratory since 1969, 1 with erythropoietic protoporphyria and the others with hepatic porphyria. In the past decade, the number of patients diagnosed during the latent phase has increased markedly. This points both to increased awareness of porphyria by physicians and to the increased skills of the laboratory staff.