Cyclooxygenase inhibitors and the antiplatelet effects of aspirin

BACKGROUND

Patients with arthritis and vascular disease may receive both low-dose aspirin and other nonsteroidal antiinflammatory drugs. We therefore investigated potential interactions between aspirin and commonly prescribed arthritis therapies

METHODS

We administered the following combinations of drugs for six days: aspirin (81 mg every morning) two hours before ibuprofen (400 mg every morning) and the same medications in the reverse order; aspirin two hours before acetaminophen (1000 mg every morning) and the same medications in the reverse order; aspirin two hours before the cyclooxygenase-2 inhibitor rofecoxib (25 mg every morning) and the same medications in the reverse order; enteric-coated aspirin two hours before ibuprofen (400 mg three times a day); and enteric-coated aspirin two hours before delayed-release diclofenac (75 mg twice daily)

RESULTS

Serum thromboxane B(2) levels (an index of cyclooxygenase-1 activity in platelets) and platelet aggregation were maximally inhibited 24 hours after the administration of aspirin on day 6 in the subjects who took aspirin before a single daily dose of any other drug, as well as in those who took rofecoxib or acetaminophen before taking aspirin. In contrast, inhibition of serum thromboxane B(2) formation and platelet aggregation by aspirin was blocked when a single daily dose of ibuprofen was given before aspirin, as well as when multiple daily doses of ibuprofen were given. The concomitant administration of rofecoxib, acetaminophen, or diclofenac did not affect the pharmacodynamics of aspirin

CONCLUSIONS

The concomitant administration of ibuprofen but not rofecoxib, acetaminophen, or diclofenac antagonizes the irreversible platelet inhibition induced by aspirin. Treatment with ibuprofen in patients with increased cardiovascular risk may limit the cardioprotective effects of aspirin.

Caffeine eliminates psychomotor vigilance deficits from sleep inertia

STUDY OBJECTIVES

This study sought to establish the effects of caffeine on sleep inertia, which is the ubiquitous phenomenon of cognitive performance impairment, grogginess and tendency to return to sleep immediately after awakening.

DESIGN

28 normal adult volunteers were administered sustained low-dose caffeine or placebo (randomized double-blind) during the last 66 hours of an 88-hour period of extended wakefulness that included seven 2-hour naps during which polysomnographical recordings were made. Every 2 hours of wakefulness, and immediately after abrupt awakening from the naps, psychomotor vigilance performance was tested.

SETTING

N/A.

PARTICIPANTS

N/A.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

In the placebo condition, sleep inertia was manifested as significantly impaired psychomotor vigilance upon awakening from the naps. This impairment was absent in the caffeine condition. Caffeine had only modest effects on nap sleep.

CONCLUSIONS

Caffeine was efficacious in overcoming sleep inertia. This suggests a reason for the popularity of caffeine-containing beverages after awakening. Caffeine's main mechanism of action on the central nervous system is antagonism of adenosine receptors. Thus, increased adenosine in the brain upon awakening may be the cause of sleep inertia.

Effect of the Pl(A2) alloantigen on the function of beta(3)-integrins in platelets

The polymorphism responsible for the Pl(A2) alloantigen on the beta(3)-component of beta(3)-containing integrins is reported to be a risk factor for coronary thrombosis. This study examined the effect of Pl(A2) on the function of beta(3)-integrins using platelets from subjects homozygous and heterozygous for Pl(A1) and Pl(A2). There was overlap in the distribution of the dissociation constant (K(d)) and maximum fibrinogen binding (B(max)) values for fibrinogen binding to alpha(IIb)beta(3) on platelets from Pl(A1) and Pl(A2) homozygotes and Pl(A1)/Pl(A2) heterozygotes. However, whereas there was no statistical difference in these values for the Pl(A1) homozygotes and Pl(A2) heterozygotes, the K(d) for the Pl(A2) homozygotes was significantly lower than that for the Pl(A1)/Pl(A2) heterozygotes, but was not statistically different from that for the Pl(A1) homozygotes. No differences were detected in ADP sensitivity between platelets from Pl(A1) homozygotes and Pl(A1)/Pl(A2) heterozygotes, in the IC(50) for RGDS inhibition of fibrinogen binding to alpha(IIb)beta(3), in the alpha(v)beta(3)-mediated adhesion of platelets to osteopontin and vitronectin, and in the phorbol ester-stimulated adhesion to fibrinogen of B lymphocytes expressing alpha(IIb)beta(3) containing either the Pl(A1) or the Pl(A2) polymorphism. Finally, no differential effects of Pl(A2) on turbidometric platelet aggregation, platelet secretion, or platelet thrombus formation were found as measured in the PFA-100. Because no differences were detected in the ability of beta(3)-integrins to interact with ligands based on the presence or absence of the Pl(A2) polymorphism, the results suggest that factors unrelated to beta(3)-integrin function may account for the reported association of the Pl(A2) allele with coronary thrombosis.

Effects of testosterone replacement in hypogonadal men

Treatment of hypogonadal men with testosterone has been shown to ameliorate the effects of testosterone deficiency on bone, muscle, erythropoiesis, and the prostate. Most previous studies, however, have employed somewhat pharmacological doses of testosterone esters, which could result in exaggerated effects, and/or have been of relatively short duration or employed previously treated men, which could result in dampened effects. The goal of this study was to determine the magnitude and time course of the effects of physiological testosterone replacement for 3 yr on bone density, muscle mass and strength, erythropoiesis, prostate volume, energy, sexual function, and lipids in previously untreated hypogonadal men. We selected 18 men who were hypogonadal (mean serum testosterone +/- SD, 78 +/- 77 ng/dL; 2.7 +/- 2.7 nmol/L) due to organic disease and had never previously been treated for hypogonadism. We treated them with testosterone transdermally for 3 yr. Sixteen men completed 12 months of the protocol, and 14 men completed 36 months. The mean serum testosterone concentration reached the normal range by 3 months of treatment and remained there for the duration of treatment. Bone mineral density of the lumbar spine (L2-L4) increased by 7.7 +/- 7.6% (P < 0.001), and that of the femoral trochanter increased by 4.0 +/- 5.4% (P = 0.02); both reached maximum values by 24 months. Fat-free mass increased 3.1 kg (P = 0.004), and fat-free mass of the arms and legs individually increased, principally within the first 6 months. The decrease in fat mass was not statistically significant. Strength of knee flexion and extension did not change. Hematocrit increased dramatically, from mildly anemic (38.0 +/- 3.0%) to midnormal (43.1 +/- 4.0%; P = 0.002) within 3 months, and remained at that level for the duration of treatment. Prostate volume also increased dramatically, from subnormal (12.0 +/- 6.0 mL) before treatment to normal (22.4 +/- 8.4 mL; P = 0.004), principally during the first 6 months. Self-reported sense of energy (49 +/- 19% to 66 +/- 24%; P = 0.01) and sexual function (24 +/- 20% to 66 +/- 24%; P < 0.001) also increased, principally within the first 3 months. Lipids did not change. We conclude from this study that replacing testosterone in hypogonadal men increases bone mineral density of the spine and hip, fat-free mass, prostate volume, erythropoiesis, energy, and sexual function. The full effect of testosterone on bone mineral density took 24 months, but the full effects on the other tissues took only 3-6 months. These results provide the basis for monitoring the magnitude and the time course of the effects of testosterone replacement in hypogonadal men.

Effect of testosterone treatment on bone mineral density in men over 65 years of age

As men age, their serum testosterone concentrations decrease, as do their bone densities. Because bone density is also low in hypogonadal men, we hypothesized that increasing the serum testosterone concentrations of men over 65 yr to those found in young men would increase their bone densities. We randomized 108 men over 65 yr of age to wear either a testosterone patch or a placebo patch double blindly for 36 months. We measured bone mineral density by dual energy x-ray absorptiometry before and during treatment. Ninety-six men completed the entire 36-month protocol. The mean serum testosterone concentration in the men treated with testosterone increased from 367 +/- 79 ng/dL (+/-SD; 12.7 +/- 2.7 nmol/L) before treatment to 625 +/- 249 ng/dL (21.7 +/- 8.6 nmol/L; P < 0.001) at 6 months of treatment and remained at that level for the duration of the study. The mean bone mineral density of the lumbar spine increased (P < 0.001) in both the placebo-treated (2.5 +/- 0.6%) and testosterone-treated (4.2 +/- 0.8%) groups, but the mean changes did not differ between the groups. Linear regression analysis, however, demonstrated that the lower the pretreatment serum testosterone concentration, the greater the effect of testosterone treatment on lumbar spine bone density from 0-36 months (P = 0.02). This analysis showed a minimal effect (0.9 +/- 1.0%) of testosterone treatment on bone mineral density for a pretreatment serum testosterone concentration of 400 ng/dL (13.9 nmol/L), but an increase of 5.9 +/- 2.2% for a pretreatment testosterone concentration of 200 ng/dL (6.9 nmol/L). Increasing the serum testosterone concentrations of normal men over 65 yr of age to the midnormal range for young men did not increase lumbar spine bone density overall, but did increase it in those men with low pretreatment serum testosterone concentrations.

Oral delivery of anticoagulant doses of heparin. A randomized, double-blind, controlled study in humans

BACKGROUND

Parenteral heparin is the anticoagulant of choice in hospitalized patients. Continued anticoagulation is achieved by subcutaneous administration of low-molecular-weight heparin or with an orally active anticoagulant such as warfarin. An oral heparin formulation would avoid the inconvenience of subcutaneous injection and the unfavorable drug interactions and adverse events associated with warfarin. A candidate delivery agent, sodium N-[8(-2-hydroxybenzoyl)amino]caprylate (SNAC), was evaluated with escalating oral heparin doses in a randomized, double-blind, controlled clinical study for safety, tolerability, and effects on indexes of anticoagulation.

METHODS AND RESULTS

Increases in activated partial thromboplastin time (aPTT), anti-factors IIa and Xa, and tissue factor pathway inhibitor (TFPI) concentrations were detected when normal volunteers were dosed with 10.5 g SNAC/20000 IU heparin by gavage in some subjects. For the entire group, 30000 IU SNAC and heparin elevated TFPI from 74.9+/-7.6 to 254.2+/-12.3 mg/mL (P<0.001) 1 hour after dosing (P<0.001). Similar changes occurred in anti-factor IIa and anti-factor Xa. aPTT rose from 28+/-0.5 to 42.2+/-6.3 seconds 2 hours after dosing (P<0.01). No significant changes in vital signs, physical examination, ECGs, or clinical laboratory values were observed. Neither 30000 IU heparin alone nor 10.5 g SNAC alone altered the hemostatic parameters. Emesis was associated with 10.5 g SNAC. A taste-masked preparation of SNAC 2.25 g was administered orally with heparin 30000 to 150000 IU. Both aPTT and anti-factor Xa increased with escalating doses of heparin. This preparation was well tolerated. Conclusions-Heparin, administered orally in combination with the delivery agent SNAC, produces significant elevations in 4 indexes of anticoagulant effect in healthy human volunteers. These results establish the feasibility of oral delivery of anticoagulant doses of heparin in humans and may have broader implications for the absorption of macromolecules.

Gonadotroph adenoma in a premenopausal woman secreting follicle-stimulating hormone and causing ovarian hyperstimulation

The clinical manifestations of gonadotroph adenomas are almost always neurological, consequences of their large size, and are rarely endocrinological. We report an exception, a 39-yr-old woman whose gonadotroph adenoma caused supranormal serum concentrations of FSH, which resulted in the development of multiple ovarian cysts, persistent elevation of her serum estradiol concentration, and endometrial hyperplasia. She initially presented because of amenorrhea at age 30 yr and was treated for an intrasellar mass by transsphenoidal surgery at age 31 yr and again at age 36 yr. Before and after the second operation she had persistently supranormal plasma estradiol concentrations (> 1840 pmol/L) and endometrial hyperplasia. When she was evaluated at age 39 yr, transvaginal ultrasound showed multiple ovarian cysts and endometrial thickening. Her plasma estradiol level was markedly supranormal (2160 pmol/L), FSH was mildly supranormal (17.8 IU/L), and alpha-subunit was markedly supranormal (23.3 micrograms/L). Characteristic of gonadotroph adenomas, her LH beta level increased by 69% in response to TRH. Neither FSH nor alpha-subunit decreased in response to administration of the GnRH antagonist, Nal-Glu-GnRH (5 mg/12 h for 4 weeks). Excised adenoma tissue exhibited morphological features of a gonadotroph adenoma. This patient appears to be unique, in that her gonadotroph adenoma caused slightly, but persistently, supranormal concentrations of FSH, which caused ovarian stimulation, including supranormal plasma estradiol concentrations, multiple ovarian cysts, and endometrial hyperplasia. We propose that gonadotroph adenomas be considered in the differential diagnosis of patients who have this constellation of abnormalities.

Contribution of potassium to exercise-induced vasodilation in humans

It has been postulated that skeletal muscle release of potassium contributes to exercise-induced vasodilation of skeletal muscle arterioles. To determine whether potassium produces muscle arteriolar vasodilation in humans, we measured plethysmographic forearm blood flow and brachial venous potassium concentrations during brachial arterial infusion of potassium (0.6, 3, 6, 15, and 30 mueq.min-1.100 ml forearm volume-1) in nine normal subjects. Infusion of potassium decreased forearm vascular resistance, with an increase in brachial venous potassium of 1 meq/l decreasing forearm vascular tone by 25-30%. We then measured plasma potassium concentrations during forearm and upright bicycle exercise in 15 normal subjects. Forearm exercise at 0.6 W decreased forearm vascular resistance by 83%, whereas brachial venous potassium increased by only 0.5 +/- 0.2 meq/l (both P < 0.05). Maximal bicycle exercise increased systemic potassium concentrations by 1.2 +/- 0.2 meq/l. These findings indicate that potassium produces muscle arteriolar vasodilation in humans and therefore supports the hypothesis that potassium release from exercising muscle contributes to exercise-induced vasodilation. The relatively small change in venous potassium noted during forearm exercise despite marked forearm vasodilation suggests that local potassium release is only a small contributor to exercise-induced vasodilation. However, potassium release during maximal exercise may have significant vasodilatory effects on arterioles both in exercising and nonexercising tissues.

Leukocytosis and natural killer cell function parallel neurobehavioral fatigue induced by 64 hours of sleep deprivation

The hypothesis that sleep deprivation depresses immune function was tested in 20 adults, selected on the basis of their normal blood chemistry, monitored in a laboratory for 7 d, and kept awake for 64 h. At 2200 h each day measurements were taken of total leukocytes (WBC), monocytes, granulocytes, lymphocytes, eosinophils, erythrocytes (RBC), B and T lymphocyte subsets, activated T cells, and natural killer (NK) subpopulations (CD56/CD8 dual-positive cells, CD16-positive cells, CD57-positive cells). Functional tests included NK cytotoxicity, lymphocyte stimulation with mitogens, and DNA analysis of cell cycle. Sleep loss was associated with leukocytosis and increased NK cell activity. At the maximum sleep deprivation, increases were observed in counts of WBC, granulocytes, monocytes, NK activity, and the proportion of lymphocytes in the S phase of the cell cycle. Changes in monocyte counts correlated with changes in other immune parameters. Counts of CD4, CD16, CD56, and CD57 lymphocytes declined after one night without sleep, whereas CD56 and CD57 counts increased after two nights. No changes were observed in other lymphocyte counts, in proliferative responses to mitogens, or in plasma levels of cortisol or adrenocorticotropin hormone. The physiologic leukocytosis and NK activity increases during deprivation were eliminated by recovery sleep in a manner parallel to neurobehavioral function, suggesting that the immune alterations may be associated with biological pressure for sleep.

Contribution of prostaglandins to exercise-induced vasodilation in humans

It has been postulated that endothelial release of prostaglandins contributes to exercise-induced vasodilation of skeletal muscle arterioles. To test this hypothesis, 12 normal subjects underwent brachial arterial and venous catheter insertion and instrumentation of their forearm to measure plethysmographic forearm blood flow. Forearm blood flow and arterial and venous 6-ketoprostaglandin F1 alpha (PGF1 alpha) and prostaglandin E2 (PGE2) were then measured during two levels of wrist flexion exercise (0.2 and 0.4 W). In nine of the subjects, exercise was repeated after intra-arterial infusion of indomethacin (0.3 mg/100 ml forearm vol). Exercise increased forearm blood flow (2.0 +/- 0.2 to 12.1 +/- 1.1 ml.min-1.100 ml-1) and forearm release of PGF1 alpha (162 +/- 28 to 766 +/- 193 pg.min-1.100 ml-1) and PGE2 (26 +/- 6 to 125 +/- 46 pg.min-1.100 ml-1) (all P < 0.05). Indomethacin virtually abolished forearm prostaglandin release and reduced forearm blood flow at rest (2.2 +/- 0.2 to 1.7 +/- 0.2 ml.min-1.100 ml-1), at 0.2 W (6.3 +/- 0.7 to 5.4 +/- 0.7 ml.min-1.100 ml-1), and at 0.4 W (12.2 +/- 1.5 to 10.3 +/- 1.3 ml.min-1.100 ml-1) (all P < 0.02). These data suggest that release of vasodilatory prostaglandins contributes to exercise-induced arteriolar vasodilation and hyperemia in skeletal muscle.

Potassium supplementation ameliorates mineralocorticoid-induced sodium retention

Potassium depletion induced by dietary potassium restriction causes sodium retention while potassium supplementation augments urinary sodium excretion. The role of external potassium balance in modulating mineralocorticoid-induced sodium retention in humans is unknown. Accordingly, eight healthy subjects were studied at the Clinical Research Center receiving a constant diet providing (per kg body wt) sodium 2.5 mmol, potassium 1.1 mmol daily. After establishing basal sodium and potassium balance over three days, each subject received 9 alpha-fludrocortisone 0.4 mg/day for 10 days. Subjects were studied twice, four to eight weeks apart, in a double blind, randomized crossover design receiving either placebo or additional KCl (80 mmol/day) over the 10 day study period. Serum potassium concentrations were unchanged from basal values on KCl while the values fell (4.1 +/- 0.1 vs. 3.4 +/- 0.1 mmol/liter, P = 0.01) on placebo. Urinary sodium excretion decreased with fludrocortisone administration in both groups, but this decrease reached significance only in the placebo group. Furthermore, during fludrocortisone administration the sodium excretion rates on KCl were significantly higher compared to the values noted on placebo (134 +/- 8 vs. 112 +/- 13 mmol/day, P = 0.01). Body weight recorded after 10 days of fludrocortisone administration was higher on placebo compared to KCl (72.3 +/- 2.8 vs. 71.6 +/- 2.8 kg, P = 0.01). Plasma renin activity, and aldosterone concentrations decreased on fludrocortisone while atrial natriuretic peptide levels increased. These studies suggest that amelioration of hypokalemia attenuates mineralocorticoid-induced sodium retention. Therefore, potassium depletion may contribute to the mineralocorticoid-induced sodium retention.

Effect of dietary protein on glomerular renin secretion

Previous studies from our and other laboratories demonstrated that dietary protein restriction lowers plasma renin activity by impairing renin release. The effect of protein intake on glomerular renin secretion has not been investigated. Accordingly, we studied male Sprague-Dawley rats weighing 180 to 200 g for 3 weeks that were receiving isocaloric diets that provided either standard 20% protein (SP) or low 6% protein (LP). Renin secretion was measured in the glomeruli isolated from these rats, at baseline and following stimulation with arachidonic acid and isoproterenol. The activity of plasma renin (3.0 +/- 0.5 ng/mL/min on SP v 1.1 +/- 0.1 ng/mL/min on LP) was significantly (P < 0.02) lower on LP intake. In contrast, glomerular renin content (22.9 +/- 0.7 ng/micrograms protein on SP v 32.3 +/- 1.4 ng/micrograms protein on LP) was significantly (P < 0.01) higher on the LP diet. Furthermore, renin secretion (ng/mL/h) from the isolated glomeruli at baseline (3.9 +/- 1.0 on SP v 12.5 +/- 3.0 on LP, P < 0.02), and following incubation with arachidonic acid 10(-5) mol/L (5.9 +/- 1.7 on SP v 19.6 +/- 3.1 on LP, P < 0.005), and isoproterenol 10(-3) mol/L (6.0 +/- 0.5 on SP v 17.3 +/- 3.3 on LP, P < 0.01) was significantly higher on the LP diet. These studies suggest that dietary protein restriction impairs in vivo renin release. In contrast, in vitro glomerular renin release is augmented by protein restriction. The factors modulating in vivo renin release require further characterization.

Natriuretic effect of calcium-channel blockers in hypertensives

This double-blind, randomized, crossover trial characterizes the acute natriuretic response to calcium-channel blockers (CCB) and investigates the role of hemodynamic and hormonal factors in mediating the natriuresis. Thirteen male subjects with essential hypertension received a single oral 20-mg dose of nifedipine or 120 mg of diltiazem. Renal functional and hemodynamic measurements were performed prior to and hourly for 4 hours following medication. Subjects then received these medications for 4 weeks at which time the above studies were repeated. Urinary sodium excretion increased within 60 minutes of CCB administration and the natriuresis was sustained for 4 hours. Cumulative sodium loss during the 4 hours of study was greater with nifedipine (43 +/- 12 mmol) than with diltiazem (18 +/- 6 mmol) (P less than 0.05). Despite natriuresis, urinary potassium excretion was decreased by both agents. Even though both drugs decreased the mean arterial pressure, inulin and paraaminohippurate (PAH) clearances were not altered. Plasma aldosterone concentrations decreased, plasma catecholamine concentrations increased, whereas plasma-renin activity was unchanged with both drugs. Body weight, glomerular filtration rate (GFR), renal plasma flow, plasma-renin activity, plasma aldosterone, and catecholamine concentrations were unchanged following 4 weeks of therapy. The acute natriuretic response after 4 weeks of therapy was similar to the response noted after the first dose. This study concludes that CCB are acutely natriuretic. Despite systemic hypotension, renal hemodynamics are unaltered during CCB therapy. Suppression of aldosterone as well as direct tubular effects of these drugs may mediate the natriuresis. Chronic therapy with CCB does not modify the acute natriuretic response to these agents.

Potassium depletion exacerbates essential hypertension

OBJECTIVE

To determine the effect of potassium depletion on blood pressure in patients with essential hypertension.

DESIGN

Double-blind, randomized, crossover study, with each patient serving as his or her own control.

SETTING

Clinical research center at a university hospital.

PATIENTS

Twelve patients with hypertension.

INTERVENTIONS

Patients were placed on 10-day isocaloric diets providing a daily potassium intake of either 16 mmol or 96 mmol. The intake of sodium (120 mmol/d) and other minerals was kept constant. On day 11 each patient received a 2-litre isotonic saline infusion over 4 hours.

MEASUREMENTS

Blood pressure; urinary excretion rates for sodium, potassium, calcium, and phosphorous; glomerular filtration rate; renal plasma flow; and plasma levels of vasoactive hormones.

MAIN RESULTS

With low potassium intake, systolic blood pressure increased (P = 0.01) by 7 mm Hg (95% CI, 3 mm Hg to 11 mm Hg) and diastolic pressure increased (P = 0.04) by 6 mm Hg (CI, 1 mm Hg to 11 mm Hg), whereas plasma potassium concentration decreased (P less than 0.001) by 0.8 mmol/L (CI, 0.4 to 1.0 mmol/L). In response to a 2-litre isotonic saline infusion, the mean arterial pressure increased similarly on both diets but reached higher levels on low potassium intake (115 +/- 2 mm Hg compared with 109 +/- 2 mm Hg, P = 0.03). Potassium depletion was associated with a decrease in sodium excretion (83 +/- 6 mmol/d compared with 110 +/- 5 mmol/d, P less than 0.001). Plasma renin activity and plasma aldosterone concentrations also decreased in patients during low potassium intake, but concentrations of arginine vasopressin and atrial natriuretic peptide, glomerular filtration rate, and renal plasma flow were unchanged. Further, low potassium intake increased urinary excretion of calcium and phosphorus and of plasma immunoreactive parathyroid hormone levels.

CONCLUSION

Dietary potassium restriction increases blood pressure in patients with essential hypertension. Both sodium retention and calcium depletion may contribute to the increase in blood pressure during potassium depletion.

Protein-induced modulation of renin secretion is mediated by prostaglandins

Dietary protein restriction inhibits glomerular prostaglandin (PG) synthesis and lowers plasma renin activity (PRA). To investigate the role of PG in mediating protein-induced alterations in renin secretion, male Sprague-Dawley rats were fed isocaloric diets providing either a standard 20% protein or a low-protein (6%) diet for 3 wk. An additional group of rats received a PG synthesis inhibitor, meclofenamate (25 mg/l), in the drinking water along with the 20% protein diet. Both protein restriction and meclofenamate administration significantly (P less than 0.025) lowered glomerular PGE2 production. Compared with standard protein intake, low protein intake lowered basal PRA (3.96 +/- 0.16 vs. 1.58 +/- 0.12 ng.ml-1.h-1, P less than 0.001), stimulated PRA (11.6 +/- 2.3 vs. 5.5 +/- 0.7 ng.ml-1.h-1, P less than 0.025), renal venous PRA (10.0 +/- 0.7 vs. 7.02 +/- 0.72 ng.ml-1.h-1, P less than 0.02), and plasma angiotensin II (ANG II) levels (52 +/- 5 vs. 24 +/- 3 pg/ml, P less than 0.01), while augmenting renal tissue renin content (2.36 +/- 0.21 vs. 3.56 +/- 0.30 micrograms/mg protein, P less than 0.005). Changes in plasma and renal tissue renin on meclofenamate treatment were similar to those observed on 6% protein diet. Both protein restriction and meclofenamate administration increased the glomerular ANG II receptor number, while the receptor affinity was unchanged. Thus protein restriction lowers PRA by impairing release of renin into circulation. This impairment in renin release is mediated by PG.

Effect of premedication on arterial blood gases prior to cardiac surgery

The effect of premedication on arterial blood gas tensions was studied in thirty adult surgical patients with valvular disease. They were divided into three groups, each group having a different premedication regimen. Blood gas tensions were compared in these patients when awake on the night before surgery, asleep, after premedication and just prior to induction of anaesthesia. Samples were taken while the patient breathed air and each patient acted as his/her own control. The patients were randomised into one of three premedication regimens: 1. intramuscular lorazepam, 2. intramuscular morphine and hyoscine (scopolamine) and 3. oral lorazepam plus intramuscular morphine and hyoscine. There was a statistically significant though not clinically significant rise in PaCO2 and fall in pH following premedication with lorazepam, morphine and hyoscine. There was also a significant fall in PaO2 associated with morphine and hyoscine premedication which was greater than that which occurred with unsedated sleep. Patients who are to undergo cardiac valvular surgery should receive supplementary oxygen following premedication and during transfer to the operating room.

Influence of 2,3-dimercaptosuccinic acid on gastrointestinal lead absorption and whole-body lead retention

2,3-Dimercaptosuccinic acid (DMSA) is a new orally active heavy metal chelator for the treatment of childhood Pb intoxication on an outpatient basis. The influence of DMSA, as well as other chelating agents, on gastrointestinal 203Pb absorption and whole-body 203Pb retention was examined. Groups of Sprague-Dawley rats (230-260 g) were gavaged with a solution containing approximately 25 mg/kg Pb [as Pb(NO3)2] plus 15 microCi 203Pb. Some groups were then immediately given 0.11 mmol/kg of either DMSA, CaNa2EDTA, D-penicillamine, or BAL by oral gavage, while other groups received the same drugs by ip injection. Control groups received solutions of the drug vehicles po or ip. Whole-body Pb retention and gastrointestinal Pb absorption (whole body retention + urinary Pb excretion) were significantly decreased in rats that received DMSA po. This finding implies that the use of DMSA to treat childhood lead intoxication on an outpatient basis is not associated with a risk for increased Pb absorption.

Localization of lead in the kidney and liver of rats treated in vivo with lead acetate: ultrastructural studies on unstained sections

The subcellular distribution and ultrastructural effects of lead have been studied in the kidneys and liver of rats given lead acetate (600 ppm Pb2+) in their drinking water for 6 months. Control rats were given sodium acetate. Tissue samples were fixed in glutaraldehyde and examined by electron microscopy with and without staining. Unstained sections of both kidney and liver from lead-treated animals showed small particles (2-5 nm diameter) of very high electron density which appear to represent a deposited form of Pb2+. Ultrastructural changes in the kidneys were largely confined to glomeruli (swelling of endothelial cells, fusion of foot processes, thickening of basement membrane) and proximal tubules (ranging from minimal sub-lethal changes to necrotic disorganization). The electron-dense particles of Pb2+ occurred in large clusters in basement membranes. As individual particles, or small groups, they were numerous in nuclei of proximal epithelium but usually only a few, largely confined to vesicles or inclusion bodies, were present in the cytoplasm. Only when cells were markedly damaged morphologically were particles more generally distributed in the cytoplasm. Liver damage by Pb2+ was largely confined to centrilobular regions. Endothelial and Kupffer cells were the most affected; they often sequestered large numbers of the particles. In parenchymal cells, particles were few and mainly in vesicles, but they were more widely distributed in the cytoplasm when morphological injury was apparent. The free distribution of Pb2+ in liver and kidney seems to be limited by its deposition in basement membranes and sequestration in reticulo-endothelial cells; intracellular distribution in healthy cells is also limited, by deposition in nuclei (in kidney only) or cytoplasmic vesicles.

Uptake of inorganic lead in vitro by isolated mitochondria and tissue slices of rat renal cortex

Slices of rat renal cortex were shown to take up Pb2+ during incubation in vitro; Pb2+ was also shown to enter mitochondria within the slices. The uptake of Pb2+ by isolated mitochondria was inhibited by N-3, La3+ and ruthenium red. A steady state of uptake was attained within 60 sec. The concentration dependence of uptake was complex; maximum uptake was attained at 25 microM and inhibition ensued at higher concentrations. A substantial inhibitor-resistant component of Pb2+ uptake was noted, especially at medium Pb2+ concentrations greater than 25 microM, and these concentrations also inhibited respiration state 3. The effects on respiration were reduced if the mitochondria had been preincubated with ruthenium red. Slices of renal cortex incubated at 1 degree in medium with various concentrations of Pb2+ showed two fractions of uptake, one saturating at 50-100 microM external Pb2+ and the other at 150-200 microM. Subsequent incubation for 60 min at 25 degrees led to further uptake at all concentrations. Upon isolation of mitochondria from incubated slices, significant amounts of Pb2+ were detected in the mitochondria within 5 min of addition of Pb2+ (200 microM), with maximum attained at 30 min. Electron microscopy of slices showed electron-dense particles, apparently of Pb2+, in the cortical cells but the greatest concentration was deposited in the basement membranes. The results indicate the importance of the basement membrane in limiting access of Pb2+ to cortical cells, and of mitochondria in accumulating Pb2+ once it is in the cells. They also illustrate the importance of interactions between Pb2+ and Ca2+.

Morphological and physiological studies of rat kidney cortex slices undergoing isosmotic swelling and its reversal: a possible mechanism for ouabain-resistant control of cell volume

Slices of rat kidney cortex were induced to swell by preincubation at 1 degree C in an isotonic Ringer's solution, and their capacity to reverse swelling, by net extrusion of cellular water, was studied during subsequent incubation at 25 degrees C. The recovery from swelling was prevented by the respiratory inhibitor, antimycin A. On the other hand, extrusion of water was little affected by ouabain. The extrusion of water continuing in the presence of ouabain (but not that in its absence) was significantly reduced when furosemide was added or when medium Cl- was replaced by NO-3 or I-. There was substantial variability in the morphological appearance of cells within the cortical slices. Different segments of the nephron showed different structural changes during swelling and its reversal, the proximal tubules being most markedly affected. Proximal tubular cells of swollen slices showed disorganization of brush borders and expansion of their apical surfaces, and contained vesicles in their apical cytoplasm. Upon recovery at 25 degrees C, the apical portions of these cells showed reversal of the expansion, but some apical vesicles remained. These vesicles were much more numerous after recovery in the presence of ouabain, but they were much reduced in numbers, or totally absent, when recovery took place in the presence of furosemide or absence of Cl-, with or without ouabain. The vesicles seen in the presence of ouabain alone appeared to fuse with each other and with infoldings of the basolateral plasma membrane. Rather similar results were obtained with distal tubular cells in the slices. We suggest that volume regulation in the proximal and distal tubular cells proceeds by way of two mechanisms. The first consists of extrusion of water coupled to the ouabain-sensitive transport of Na+ and K+. The other proceeds by way of an ouabain-resistant entry of water into apical cytoplasmic vesicles, following furosemide-sensitive movements of Cl- and Na+; the vesicles then expel their contents by exocytosis at the basolateral cell borders.

Effects of inorganic lead in vitro on ion exchanges and respiratory metabolism of rat kidney cortex

The effects of Pb2+ added in vitro to tissue slices, isolated tubules and isolated mitochondria of rat kidney cortex have been studied. Slices were depleted of K+ and loaded with Na+, Cl- and water by pre-incubation at 1 degree C, and reversal of these changes was then induced by incubation under metabolically favourable conditions. The net reaccumulation of K+ was reduced by a maximum of 30% when Pb2+ was present in the medium, the maximal effect being caused by 200 microM Pb2+. Lead also caused a reduction of Na+ extrusion which was approximately equimolar with its effect on K+, but it did not affect the extrusion of Cl- and water. The initial rates of the net, active movements of K+ and Na+ were not altered by Pb2+, divergence from control values only being noted after 15-30 min incubation. The O2 consumption and the ATP content were 25-30% lower in slices incubated with 200 microM Pb2+ than in control slices; the effect on ATP content was not observed until incubation had continued for 30 min. In tubules isolated from the renal cortex, the rate of respiration (50%) and ATP content (30%) were also partly reduced by 200 microM Pb2+. The consumption of O2 by mitochondria isolated from the cortex was much more sensitive to Pb2+ added in vitro than the respiration of intact cells; the rate of respiration in state 3 (presence of phosphate acceptor) and the respiratory control ratio were drastically reduced, with half-maximal inhibition at 30 and 20 microM Pb2+ respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Pb2+ added in vitro on Ca2+ movements in isolated mitochondria and slices of rat kidney cortex

We have studied the effects of Pb2+ added in vitro on the movements of Ca2+ in renal cortical mitochondria and tissue slices. The isolated mitochondria rapidly accumulated 45Ca2+ at 25 degrees by a mechanism that was dependent on respiration and inhibited 96% by ruthenium red. A concentration of 10 microM Pb2+ inhibited the Ca2+ accumulation at least as effectively as did ruthenium red. About 20% of the Ca2+ accumulation persisted at 1 degrees with a similar sensitivity to inhibitors, including 60% inhibition by Pb2+. Similar results were obtained when the accumulation of Ca2+ at 25 degrees was measured by means of a calcium-sensitive electrode, Pb2+ inhibiting by 80%. Calcium that had been accumulated by mitochondria at 25 degrees was released completely by the ionophore A23187 or by 10 microM Pb2+. The release induced by Pb2+ was greatly inhibited by ruthenium red. The Ca2+ content of tissue slices of renal cortex increased 4-fold during incubation at 1 degree while the Ca2+ content of mitochondria within the slices more than doubled, the latter being determined by isolation of mitochondria from the slices after incubation. The presence of Pb2+ (200 microM) in the incubation medium of the slices substantially reduced the entry of Ca2+ into the whole slices and into mitochondria within the slices. When the slices preincubated at 1 degree were warmed to 25 degrees in oxygenated medium, they brought about a net extrusion of Ca2+, some of which was derived from the mitochondria; Pb2+ did not alter the final level of Ca2+ then attained in the slices, but it caused a significant decrease in the quantity retained in the mitochondria. We conclude that Pb2+ both inhibits the uptake of Ca2+ by renal cortical mitochondria and displaces Ca2+ from them, these effects occurring whether the mitochondria are isolated or in situ.

Inhibition of mitochondrial oxidative metabolism by SKF-525A in intact cells and isolated mitochondria

We have examined the effects of various concentrations of SKF-525A (beta-diethylaminoethyldiphenylpropyl acetate X HCl) on the energy metabolism of liver slices, isolated liver mitochondria, and two types of ascites tumor cells, as well as on ion transport in liver slices. In liver slices, 0.2 to 1.0 mM SKF-525A caused an initial stimulation of O2 uptake which was followed, at 0.5 to 1.0 mM, by a progressive inhibition of O2 consumption, a fall of slice ATP content, and a reduced transport of K+, Na+ and Ca2+. In isolated mitochondria, we studied the effects of SKF-525A on the rate of respiration and on the oxidation-reduction responses of NAD(P)+ and cytochrome b in the presence of various substrates. The results suggest that SKF-525A had three distinct actions on liver mitochondria, viz. an uncoupling action at low concentrations (0.02 to 0.17 mM); at higher concentrations (0.2 to 0.5 mM) an inhibition of the oxidation of NAD(P)+-linked substrates, exerted close to the substrate level; also at 0.2 to 0.5 mM, a less effective inhibition of electron transfer at a point between cytochrome b and O2 in the electron-transfer chain. Experiments on O2 consumption and cytochrome b oxidation-reduction changes in ascites cells showed only the first two of these effects in the intact tumor cells. We conclude that inhibition of mitochondrial energy-conserving reactions by SKF-525A can have a marked influence on energy-requiring aspects of liver-cell metabolism, one example of which is inhibition of cation active transport.

A study of drug resistance among Salmonella typhi and Salmonella paratyphi A in an endemic area, 1977-79

Tests for antibiotic resistance were carried out on 198 strains of Salmonella typhi and S. paratyphi A isolated from cases of enteric fevers. Their minimal inhibitory concentrations for streptomycin, chloramphenicol, ampicillin, furazolidine and co-trimoxazole were estimated by plate dilution technique. Four strains of S. typhi and one strain of S. paratyphi A were found to show multiple resistance with a set pattern of resistance to chloramphenicol, streptomycin, sulphonamide, tetracycline and spectinomycin. All the five strains carried R-factors. Three of the resistant S. typhi belonged to Phage type 'O' and one was in Phage type 'A'. The single resistant S. paratyphi A belonged to Phage type '2'.