Issue published September 1, 1970

T his study was designed to assess atrial booster pump action in valvular heart disease and to dissect booster pump from reservoir-conduit functions. In five patients with aortic stenosis and six with mitral stenosis, sequential atrioventricular (A-V) pacing was instituted during the course of diagnostic cardiac catheterization. Continuous recording of valvular gradient allowed estimation of flow for each cardiac cycle by transposition of the Gorlin formula. Left ventricular ejection time and left ventricular stroke work in aortic stenosis or left ventricular mean systolic pressure in mitral stenosis were also determined. Control observations were recorded during sequential A-V pacing with well-timed atrial systole. Cardiac cycles were then produced with no atrial contraction but undisturbed atrial reservoir function by intermittently interrupting the atrial pacing stimulus during sequential A-V pacing. This intervention significantly reduced valvular gradient, flow, left ventricular ejection time, and left ventricular mean systolic pressure or stroke work. Cardiac cycles were then produced with atrial booster action eliminated by instituting synchronous A-V pacing. The resultant simultaneous contraction of the atrium and ventricle not only eliminated effective atrial systole but also placed atrial systole during the normal period of atrial reservoir function. This also significantly reduced all the hemodynamic measurements. However, comparison of the magnitude of change from these two different pacing interventions showed no greater impairment of hemodynamic state when both booster pump action and reservoir function were impaired than when booster pump action alone was impaired. The study confirms the potential benefit of well placed atrial booster pump action in valvular heart disease in man.

T he effect of hypermagnesemia, produced by MgCl₂ infusion, on the activity of parathyroid glands, as assessed by changes in levels of serum calcium (S_Ca) and in the fraction of filtered phosphate excreted (C_P/C_Cr), was studied in 11 intact and 4 thyroparathyroidectomized (T-PTX) dogs. To exclude the effect of diurnal variation in C_P/C_Cr on the results, studies were initiated in both morning and afternoon hours and each study with MgCl₂ infusion was paired with a control experiment in the same dog not receiving MgCl₂. During MgCl₂ infusion, serum phosphorus rose progressively. Despite this rise, the levels of C_P/C_Cr fell in all experiments and were significantly different from values observed at the same time of the day in the paired control experiments. The concentrations of total S_Ca fell by 1.0-2.4 mg/100 ml with a proportional decrease in the levels of the diffusible and ionized fractions. The pattern of the fall in C_P/C_Cr during MgCl₂ resembled that observed after CaCl₂ infusion (seven dogs) and that which acutely followed thyroparathyroidectomy (seven dogs). When parathyroid extract was given to dogs receiving MgCl₂ infusion both C_P/C_Cr and S_Ca rose, and MgCl₂ infusion did not affect C_P/C_Cr and S_Ca in T-PTX dogs. These results indicate that hypermagnesemia suppresses the activity of the parathyroid glands, probably, by inhibiting production and (or) release of the hormone, without interfering with end-organ response. An increase in serum magnesium of 1.7-2.0 mg/100 ml was capable of producing the suppressive effect. Evaluation of the effect of simultaneous modest hypocalcemia and hypermagnesemia suggests that a decrease in the level of serum calcium is more potent than an increase in the concentration of serum magnesium in the regulation of parathyroid activity.

E thacrynic acid, a potent inhibitor of sodium reabsorption in the ascending limb of Henle's loop, produces a sharp rise in renal venous renin activity within 5 min after intravenous administration in anesthetized dogs. This response persists when volume depletion is prevented by returning urinary outflow to the femoral vein. Comparable studies with chlorothiazide, a diuretic with little or no effect on the medullary portion of the ascending limb of the loop of Henle, failed to produce a significant increase in renal venous renin activity.When administered during ureteral occlusion, ethacrynic acid produced no change in renal venous renin activity until ureteral occlusion was released and flow restored. Following release of the ureters, a prompt rise in renal venous renin was again observed within 5 min of release. Control studies of ureteral occlusion yielded a fall in renal venous renin activity following release of the ureter without administration of ethacrynic acid. These studies identify a prompt stimulatory effect of ethacrynic acid on renin release that is unrelated to volume depletion but dependent upon the presence of tubular urine flow. Although further definition of the site and characteristics of the distal tubular mechanism for stimulation of renin release requires more direct study, the data presented here indicate that changes in sodium concentration in distal tubular fluid serve as a stimulus for renin release.

R at parathyroid glands maintained in organ culture secrete biologically active parathyroid hormone (PTH) and synthesize and secrete labeled proteins from ³H- or ¹⁴C-labeled amino acids added to the medium. The amounts of biological activity and labeled protein in the medium are both inversely proportional to the calcium concentration. Some of the labeled low molecular weight protein was identified as PTH which had been synthesized and secreted in culture by preliminary isolation on Sephadex G-100 columns and further purification using an antibody to bovine PTH which cross-reacted with rat PTH. The cross-reacting antibody inhibited the biological effects of rat PTH and caused hypocalcemia in intact rats. The antibody bound some of the labeled low molecular weight protein of the medium at neutral pH so that it migrated as a large molecular weight complex on Sephadex. Biologically active, labeled PTH was recovered by dissociation of this complex in acid and rechromatography.

I ntact rat diaphragms were exposed in vitro to varying CO₂ tensions and bicarbonate concentrations, and the steady-state citrate content of diaphragm muscle was measured to investigate the relationship between metabolism and extracellular pH, P_CO2, and (HCO₃^-). In addition, rat hemidiaphragms were incubated with 1,5-citrate-¹⁴C under different acid-base conditions, and ¹⁴CO₂ production was determined as a measure of citrate oxidation.Acidification of the bathing medium achieved by raising CO₂ tension or lowering (HCO₃^-) was associated with a decrease in muscle citrate content. On the other hand, alkalinization of the medium induced by lowering CO₂ tension or raising (HCO₃^-) caused tissue citrate content to rise. At a physiologic extracellular pH value of approximately 7.40, citrate content was decreased or normal depending on the CO₂/HCO₃^- combination employed to attain the pH. Under low bicarbonate and low P_CO2 conditions, citrate content was reduced. A similar result was found at external pH values of 7.15, implying that at these two extracellular pH levels (HCO₃^-) primarily determines citrate content. When changes in citrate content were compared with intracellular pH data reported earlier using the same intact diaphragm preparation, no simple relation between citrate content and intracellular pH was found. The effect of acidity on citrate content seems related to a change in citrate oxidation since the latter increased progressively with increasing degrees of medium acidity.These results show that cellular metabolism is not a simple function of extracellular pH but is dependent on the particular combination of P_CO2 and bicarbonate employed to achieve the pH value. These studies also suggest that accumulation or disposal of organic acids, such as citric acid, helps to regulate cellular acidity thereby contributing to the cells' defense against external acid-base disorders.

T he effects of hematocrit on renal hemodynamics and sodium excretion were studied in anesthetized dogs during both hydropenia and volume expansion. The hematocrit was decreased by isovolemic exchange with the animal's own previously harvested plasma and increased by isovolemic exchange with fresh, washed red blood cells. Renal perfusion pressure was maintained constant throughout the experiments by the adjustment of a suprarenal aortic clamp. During hydropenia, a decrease in hematocrit was associated with an increase in sodium and potassium excretion and solutefree water reabsorption. These changes were accompained by an increase in renal plasma flow and renal blood flow and a decrease in renal vascular resistance. Glomerular filtration rate was unchanged and filtration fraction was significantly decreased as hematocrit was lowered. Increasing hematocrit during hydropenia had the opposite effects on electrolyte excretion, solute-free water reabsorption, and renal hemodynamics. In another group of animals, hematocrit was lowered during volume expansion with either saline or plasma, then returned to the control level by isovolemic exchange with washed red blood cells. This increase in hematocrit during volume expansion had a similar effect on electrolyte excretion, solute-free water reabsorption, and renal hemodynamics as during hydropenia. These results therefore suggest that acute changes in hematocrit may significantly affect sodium excretion and renal hemodynamics during both hydropenia and volume expansion. The changes in solute-free water reabsorption and potassium excretion suggest that the alterations in hematocrit may affect primarily the reabsorption of sodium in the proximal tubule. The concommitant effects of hematocrit on renal vascular resistance and filtration fraction may mediate this change in sodium reabsorption by altering hydrostatic and oncotic pressures in the peritubular circulation.

T o study the catabolism of erythrocyte phospholipids, human erythrocytes were labeled with radioactive fatty acid (FA). Labeling was performed by the two separate routes which together are thought to be responsible for the majority of phosphatide renewal in the red cell: (a) passive equilibration of erythrocytes with preformed acid-labeled red cell phosphatidylcholine (PC) and (b) active, “acylase”-dependent, incorporation of free fatty acid in the presence of ATP coenzyme A and magnesium. (As measured here “acylase” = the over-all effect of fatty acid thioesterification and the action of acyl-CoA: acylglycerophosphoryl acyltransferase.) The labeled cells were then reincubated in serum and the loss of radioactivity from cells into serum was examined.The phosphatide fatty acid introduced by these two routes was incorporated into two distinct cellular phosphatide pools with little mixing. The fatty acid in passively introduced phosphatidyl choline was released primarily as the intact phosphatide, whereas actively incorporated PC fatty acid was released primarily as free FA. As expected for an exchange process, the passively introduced PC was released at the same rate as it was introduced. However, the actively incorporated FA was released from the cell at a slower rate than its incorporation into PC. This latter phenomenon was explained by the observation of transfer of PC fatty acid to phosphatidyl ethanolamine and “neutral lipid” before its release to serum. This transfer process was inhibited by previous heating of the reincubation serum.The differences in the character of the released label, in the rate of release of the label, and in the influence of the reincubation serum all indicate separate pathways for the renewal of phosphatide introduced into red cells by these two routes.

T he serum concentration of all subclasses of IgG (γ₂A, γ₂B, and γ₁) as well as IgA and IgM were reduced in normal and low pathogen mice receiving hydrocortisone acetate. Turnover studies using ¹³¹I-labeled γ₂A subclass of IgG demonstrated that high dose corticosteroids cause a significantly shortened survival (increased catabolic rate) which contributes to the observed hypogammaglobulinemia. This increase in fractional catabolism is not due to excess loss in the urine or stool but reflects an increase in endogenous catabolism.

T he metabolism of FFA and ketone bodies was studied in fasted rats by infusing at a constant rate tracer amounts of FFA-³H, β-hydroxybutyrate-¹⁴C or acetoacetate-¹⁴C for periods up to 2 hr. Blood that was removed for analyses was replaced by continuous transfusion. The rates of turnover of FFA, β-hydroxybutyrate, and acetoacetate in rats fasted for 2 days were, respectively, 3.2, 5.6, and 2.5 μmoles/100 g body weight per min.Infusion of mannoheptulose with anti-insulin serum increased plasma glucose, FFA, and ketone body concentrations and decreased the specific activity of plasma FFA. Injection of insulin (20 mU i.v.) decreased almost simultaneously plasma glucose, FFA, and ketone body concentrations and increased the specific activity of FFA, but it did not affect the plasma concentration of FFA-³H. The findings indicate that insulin deprivation increased and insulin injection decreased the release of FFA from body tissues in fasting rats.The plasma FFA concentration in fasting rats was increased by infusing chylomicrons and heparin, but this had very little effect on either plasma ketone body or glucose concentrations. Insulin injection (20 mU i.v.) lowered the plasma ketone body concentration in these animals. Studies using β-hydroxybutyrate-¹⁴C showed that insulin (50 mU i.v.) decreased ketogenesis in the presence of a sustained high plasma FFA concentration and had no effect on uptake of circulating ketone bodies.The results indicate that plasma FFA concentration is not the sole determinant of plasma ketone body concentration and that insulin can suppress ketone body production through some means other than lowering plasma FFA concentration.

S erum levels, urinary excretion, and clearances of several proteins of different molecular weights were studied in 18 patients with mono- and myelomonocytic leukemia. Nine patients had normal renal function (group A) and nine had impaired renal function with azotemia (group B). The majority of patients in both groups had increased concentration of immunoglobulins, particularly IgG, IgA, and IgM; IgD level was normal. Serum transferrin and α₂-macroglobulin were frequently reduced while the level of ceruloplasmin was often increased, especially in patients with azotemia. The activity of lysozyme in the serum was high in all patients, but was considerably higher in group B.Proteinuria was found in most patients but was more prominent in group B. Almost invariably albumin constituted less than 25% of the total protein excreted. Qualitative analysis of various urinary proteins by immunochemical techniques and clearance studies suggested the presence of glomerular as well as tubular dysfunction. Determination of urinary lysozyme frequently showed no direct correlation between the serum level of the enzyme and its concentration in the urine or its clearance by the kidney. In addition to glomerular filtration, impaired tubular reabsorption may account for the high level of lysozyme in the urine. It is postulated that the very high level of lysozyme in the glomerular filtrate and possibly hypergammaglobulinemia may play a role in the induction of tubular damage. Renal impairment has been correlated with histological changes in the kidneys. From a comparative study of various leukemias, it seems that the combined glomerular-tubular dysfunction is a manifestation unique to mono- and myelomonocytic leukemia.

R abbits in which thrombocytosis had been produced by five daily transfusions of platelet concentrates had suppressed endogenous thrombopoiesis, as reflected by decreased incorporation of selenomethionine-⁷⁵Se (⁷⁵SeM) into the circulating platelet mass. Rabbits in which endogenous thrombopoiesis had been suppressed by transfusion-induced thrombocytosis were used to detect thrombopoietic activity in rabbit plasma. Thrombopoietic activity was demonstrated in the plasma of both normal and thrombocytopenic donor rabbits. A dose response relationship was observed between the incorporation of ⁷⁵SeM into platelets and the dose of plasma administered. Infusion of 20-150 ml of plasma from thrombocytopenic donors increased the incorporation of ⁷⁵SeM into platelets from 52 to 107% above control values. A dose response effect also was seen after infusion of normal plasma, but normal plasma produced less effect than comparable doses of plasma from thrombocytopenic donors.Rabbits with transfusion-induced thrombocytosis appear to be more sensitive assay animals for the detection of thrombopoietic activity than animals with normal platelet counts. Changes in the rate of appearance and levels of ⁷⁵SeM may primarily indicate changes in platelet protein or platelet size and are apparently more sensitive indicators of the state of thrombopoiesis than are alterations in the numbers of circulating platelets. The results strongly support the concept of a humoral agent, i.e. thrombopoietin, that acts on megakaryocytes to regulate platelet production.

H ydrocortisone sodium succinate (Solu-Cortef; Upjohn Co., Kalamazoo, Mich.) has been found to induce choleresis in unanesthetized fasting dogs fitted with Thomas duodenal cannulae for direct quantitative collection of bile. In all experiments, bile flow increased (average, 68%) 15-20 min after beginning hydrocortisone by infusion in association with an equivalent increment in the output of sodium, potassium, chloride, and bicarbonate. In five animals, the choleretic response occurred independently of, and apparently additive to, the effect of simultaneously administered sodium taurocholate. The fluid added to the bile resembled an ultrafiltrate of plasma. Erythritol clearance increased in proportion to flow, suggesting an effect at the hepatocellular rather than ductal level and probably independent, therefore, of endogenous secretin release. Hydrocortisone and its metabolites were excreted in amounts too small to induce choleresis osmotically. Simultaneous administration of sulfobromophthalein sodium blocked the choleretic response without preventing hydrocortisone excretion. The data suggest that a previously ill-defined mechanism of canalicular bile formation, not mediated by bile salt excretion, may be operative in choleretic response to a variety of agents.

I n order to determine whether or not antidiuretic hormone (ADH) is essential to the inhibition of an acute water diuresis in adrenal insufficiency, the response to oral water loads was tested in rats with hereditary hypothalamic diabetes insipidus (DI) which lack ADH. It was found that 60 min after water loads of 3 or 5% of body weight urine flow was significantly lower and urine osmolality significantly higher in adrenalectomized DI rats than in the same DI rats before removal of their adrenal glands.The efficacy of gluco- and mineralocorticoids in reversing the inhibition was then determined in the same adrenalectomized DI rats. Prednisolone alone, administered either acutely or chronically, restored the response in urine flow to that seen in the same rats before adrenalectomy, but failed to correct the defect in urinary dilution. Aldosterone when given alone tended to correct the diluting ability but not the response in urine flow. When these two adrenal cortical hormones were given simultaneously, both the urine flow and urine osmolality were nearly identical to what they had been in the same DI rats before adrenalectomy.These studies strongly suggest (a) that ADH is not essential to the inhibition of an acute water diuresis in adrenal insufficiency, although it may abet the inhibition in individuals without diabetes insipidus, which can elaborate ADH; and (b) that both gluco- and mineralocorticoids are required in adrenal insufficiency in order to fully restore the water diuresis as judged by the dual criteria of urine flow and urine osmolality.

T o explore the relation between androgens and prostatic hypertrophy in man, the concentrations of testosterone, dihydrotestosterone, and androstenedione and the rate of conversion of testosterone to dihydrotestosterone have been measured in normal and hypertrophic prostate tissue. First, a double isotope derivative technique was adapted for the measurement of tissue androgen content in 15 normal and 10 hypertrophic prostates. Although there was no significant difference in the content of androstenedione and testosterone between the two types of tissue, the content of dihydrotestosterone was significantly greater in the hypertrophic tissue (0.60 ±0.10 μg/100 g) than in the normal glands (0.13 ±0.05 μg/100 g). Second, a regional study was performed in three normal prostates and four glands with early hypertrophy, and it was demonstrated that the dihydrotestosterone content was two and three fold greater in the periurethral area where prostatic hypertrophy usually commences than in the outer regions of the gland. Finally, the rate of conversion of testosterone to dihydrotestosterone has been measured under standardized conditions in tissue slices from 4 normal and 20 hypertrophic prostates. There was no significant difference in the rate of dihydrotestosterone formation between the two types of gland (6.0 ±0.8 and 7.8 ±0.5 μμmoles/15 mg of tissue per hr). While the mechanism by which dihydrotestosterone accumulation occurs remains unexplained, it is possible that the local accumulation of dihydrotestosterone may be involved in the pathogenesis of prostatic hypertrophy in man.

T hree types of studies have been performed in immature, mature, and hypertrophic prostate glands of the dog. First, the concentrations of testosterone and dihydrotestosterone have been measured in the three types of gland. Dihydrotestosterone was the predominant hormone recovered in all prostates studied and was present in approximately five times higher concentration in the hypertrophic as compared to the other types of dog prostate. Second, pharmacological doses of dihydrotestosterone were administered to castrated dogs for 9 months and resulted in a distinct acceleration of prostatic growth as compared to testosterone treatment. Third, the rates of formation and degradation of dihydrotestosterone were measured in normal and hypertrophic tissue and were found to be essentially the same. These observations suggest that dihydrotestosterone accumulation may be causally linked to the development of canine prostatic hypertrophy. However, the mechanism by which dihydrotestosterone accumulates in the prostate remains to be determined.

A radioimmunoassay for human plasma retinol-binding protein (RBP) has been developed utilizing a double antibody precipitation technique. RBP was purified 1500- to 2000-fold by procedures described previously. A specific anti-human RBP antiserum was prepared in rabbits by three once-weekly injections of purified RBP emulsified with Freund's adjuvant. RBP was iodinated with ¹³¹I and the RBP-¹³¹I was purified by gel filtration on Sephadex G-100 after complex formation with human plasma prealbumin. The RBP-¹³¹I was completely (> 95%) immunoprecipitable in the presence of an excess of specific antiserum, it was not (< 5%) immunoprecipitable in the absence of specific antiserum, and it could be completely displaced from antibody by excess unlabeled RBP. The standard curve obtained in the immunoassay with normal plasma was identical to that with pure RBP. Duplicate samples differed from their mean by 5 ±5% (±SD). There was a quantitative recovery of pure RBP added in varying amounts to normal plasma. The immunoassay accurately measured RBP in amounts of 10-100 ng per assay tube. There was no significant difference in the immunoreactivity of apo-RBP as compared to holo-RBP. The mean plasma values (±SEM) for a group of 76 normal subjects were 47.2 ±1.6 μg/ml for males and 41.6 ±1.6 μg/ml for females. Plasma RBP levels were markedly depressed (15 ±2.3 μg/ml) in 14 patients with acute viral hepatitis. There was a highly significant correlation between the plasma levels of RBP and of vitamin A in both normal subjects and patients with hepatitis. In all subjects plasma RBP was generally saturated with retinol. The data suggest that under normal circumstances RBP circulates almost exclusively as the holoprotein.

W e investigated the effect of pyridoxine administration in three patients with homocystinuria due to cystathionine synthase deficiency. The drug decreased the plasma concentration and urinary excretion of methionine and homocystine and the urinary excretion of homolanthionine and the homocysteine-cysteine mixed disulfide. Urinary cystine rose somewhat. Oral methionine tolerance tests before and during the patients' response to pyridoxine indicated that during response they remained deficient in their capacity to convert the sulfur of methionine to inorganic sulfate, although this capacity increased somewhat. During pyridoxine response only, the methionine loads caused increased homocystinuria. There was no indication that pyridoxine stimulated an alternate pathway of metabolism. The values for specific activity of cystathionine synthase in liver biopsy specimens from two patients in pyridoxine response were 3 and 4% of the mean control value. When these patients were not receiving pyridoxine, comparable values were 2 and 1%, respectively. The hepatic enzyme activity of the mutant patients was similar to normal enzyme activity with respect to trypsin activation, heat inactivation, and stabilization by pyridoxal phosphate. Approximate estimates were made of the relation between total body capacity to metabolize methionine and hepatic cystathionine synthase activity. These estimates suggested that because of the large normal reserve capacity of cystathionine synthase, a few per cent residual activity is sufficient to metabolize the normal dietary load of methionine. Thus, small increases in residual capacity may be of major physiological importance. However, many liver biopsies would be required to establish unequivocally that such changes were due to the administration of a particular therapeutic agent rather than to biological variation. All the data in the present study are consistent with the interpretation that pyridoxine does act by causing an increase in residual cystathionine synthase activity.