Preferential transport of glutathione versus glutathione disulfide in rat liver microsomal vesicles

A bi-directional, saturable transport of glutathione (GSH) was found in rat liver microsomal vesicles. GSH transport could be inhibited by the anion transport blockers flufenamic acid and 4, 4'-diisothiocyanostilbene-2,2'-disulfonic acid. A part of GSH taken up by the vesicles was metabolized to glutathione disulfide (GSSG) in the lumen. Microsomal membrane was virtually nonpermeable toward GSSG; accordingly, GSSG generated in the microsomal lumen could hardly exit. Therefore, GSH transport, contrary to previous assumptions, is preferred in the endoplasmic reticulum, and GSSG entrapped and accumulated in the lumen creates the oxidized state of its redox buffer.

Specific contributions of various muscle fibre types to human muscle performance: an in vitro study

Human skeletal muscle fibres can be divided in five groups: 1, 1-2A, 2A, 2A-2B and 2B, by using myosin heavy chain (MHC) isoforms as molecular markers. This study aimed to define the contribution of each fibre type to the contractile performance of human muscles. Single fibre segments were dissected from bioptic samples of vastus lateralis and chemically skinned. Force-velocity properties, including isometric tension (P0), maximal shortening velocity (Vmax), maximum power output (Wmax) and the velocity at which Wmax is reached (Vopt), were determined at maximum calcium activation. Among these parameters Wmax showed the largest range of variation: about nine times between 2B and slow fibres. Vopt also showed large (about four times) and significant variations between fibre types. Force development at submaximum calcium activation was studied and force-pCa curves were obtained for each fibre type. Calcium sensitivity was greater in 2B than in 2A and in slow fibres. The slope of the force-pCa curve was greater in fast than in slow fibres. At the end of the experiment the MHC isoform composition of each fibre segment was determined by gel electrophoresis. The functional properties of each fibre type are discussed in the light of the motor unit recruitment mechanism to understand their possible physiological role.

An initial experience using concurrent paclitaxel and radiation in the treatment of head and neck malignancies

BACKGROUND

Combined modality therapy plays a central role in the management of head and neck malignancies. This study examined the feasibility and preliminary results of treating a group of patients using concurrent bolus paclitaxel (Taxol) and radiation therapy.

METHODS

Fourteen patients with a median age of 56 years (range 42-81) were treated. Paclitaxel was given every 3 weeks at a dose of 100 mg/m2 concurrently with external beam radiation. The patients treated included those who had failed to achieve a complete response (CR) to induction chemotherapy with cisplatin, 5-fluorouracil, and leucovorin (PFL), or who had locally advanced disease not previously treated.

RESULTS

Median follow-up from the initiation of treatment is 40 months (range 23-48). The majority of patients (13/14) achieved clinical CRs at the primary site. The development of responses was characterized by a long time course. Three patients who were nonresponders (NRs) to induction PFL chemotherapy were treated. One was a clinical CR at the primary site, one did not achieve a CR, and the other had residual disease in the neck. Four patients have failed, one with local-regional disease, one with a marginal failure, one with distant metastases, and one was not rendered disease-free by the treatment. As expected, significant local toxicity was observed. Most patients were managed with the aid of a percutaneous endoscopic gastrostomy (PEG). Two patients experienced significant moist desquamation and required treatment breaks of greater than 1 week.

CONCLUSION

Paclitaxel can be given on a 3-week schedule at 100 mg/m2 concurrently with radiation. The preliminary results indicate good local responses and acceptable toxicity. This treatment approach merits further study in the treatment of head and neck malignancies, and should be considered as an option in other sites.

Primary tuberculosis of the penis

We present a case of primary tuberculosis of the inner lining of the prepuce in a 63-year-old man. The condition resembled carcinoma. The diagnosis was based on histopathology and on M. tuberculosis culture. Successful treatment was by a combined medical and surgical approach. The rarity of the case is emphasized.

[Laparoscopic adrenalectomy. Initial results of a Chilean experience]

BACKGROUND

Laparoscopic adrenal approach was introduced in 1992 and is becoming the surgical method of choice for several adrenal diseases.

AIM

To report the initial Chilean experience in laparoscopic adrenalectomy.

MATERIAL AND METHODS

A retrospective review of 17 patients subjected to the surgical procedure by the authors.

RESULTS

The preoperative diagnosis were adenomas (8 patients), pheochromocytoma (3), cystic lesions (2), adrenal metastases (2), hyperaldosteronism (1) and a pituitary Cushing (1). The average lesion size was 5.4 cm, the operative time 2.5 hours and the hospital stay 2.5 days. Eight patients were discharged in less than 48 hours. Pain was managed with non steroidal antiinflammatory drugs in 14 patients. One subject required conversion to open surgery. Transfusions were required in complex cases with a diaphragmatic hamartoma, Cushing disease and in a combined adrenal and renal resection. One patient had to be re admitted due to a pancreatic pseudo cyst that was drained percutaneously. There have been no recurrences after a mean follow up of 2 years.

CONCLUSIONS

This early experience with laparoscopic adrenalectomy shows good results. A good patient selection and experience with advanced laparoscopic surgery are requisites for a successful use of this surgical technique.

Development of ifosfamide-induced nephrotoxicity: prospective follow-up in 75 patients

PURPOSE

This study was performed to describe prospectively the development and prognosis of severe ifosfamide-induced nephrotoxicity and to define the period of recommended renal follow-up after ifosfamide chemotherapy.

PATIENTS AND METHODS

Renal function was followed in 75 patients after cessation of chemotherapy starting within the first year off therapy; median follow-up time was 31 months. The glomerular filtration rate was estimated by using the Schwartz formula. Proximal tubular transport capacities were evaluated for amino acids, phosphate, sodium, and glucose. In addition, serum bicarbonate level and alkaline phosphatase were measured.

RESULTS

Five patients developed renal Fanconi syndrome during follow-up, and another seven patients developed a generalized subclinical tubulopathy. The latter condition always preceded Fanconi syndrome. Severe impairment of amino acid and phosphate reabsorption was seen in 28% and 17.3% of patients, respectively. Reductions in amino acid reabsorption preceded impairment of phosphate reabsorption. In patients with early impairment of phosphate reabsorption, renal prognosis was poor, whereas normal or only mildly impaired amino acid handling virtually excluded progressive tubular damage.

CONCLUSIONS

Ifosfamide-induced renal tubular damage is a potentially progressive disease. Along with measurement of phosphate reabsorption, additional assessment of tubular amino acid handling is suggested, because it allows early discrimination of poor from favorable renal outcomes.

[Primary absolute anorgasmy in the male. Report of three clinical cases]

Primary absolute anorgasmia is the impossibility to have orgasm and ejaculation during wake or every kind of sexual activity, in men with normal erectile function and nocturnal emission. In this syndrome the nervous system is unimpaired; the frequency is very low, with a very small number of reported cases in literature. Andrologists are generally requested by the patients for the first clinical approach. They should collaborate with sexologists for the diagnosis and treatment. Personal experience in 3 cases of anejaculatory men aged between 28 and 34, observed in the years 1995-1996, is presented and the clinical features of the patients and therapeutic strategy described. In two cases a sexual behavioral therapy was performed with success; in the third an electrovibration was employed to obtain the first orgasmic sensation.

Renal involvement in children with malignancies

Renal complications in children with malignancies primarily arise from renal parenchymal tumors, "tumor lysis syndrome," and malignant infiltration or obstruction of the urinary tract. Therapy-associated renal side effects may develop following surgical and cytostatic treatment or be induced by radiotherapy. Clinically, both acute renal failure, for example following cisplatin, or chronic dysfunction, following ifosfamide and resulting in growth failure, are observed. Frequencies of renal impairment in these patients are, however, not well established, but terminal renal failure is a rare event: pediatric malignancies account for only 0.9% of patients on renal replacement therapy; the majority of these patients had been treated for a bilateral nephroblastoma. Since potentially serious long-term renal sequelae may evolve following both single measures and additive nephrotoxic effects, long-term monitoring of growth, blood pressure, and renal function is mandatory for a great proportion of former pediatric oncology patients. Future research should prospectively address frequencies of long-term renal impairment in these patients and should establish the prognosis of renal dysfunction. Only these data will ultimately allow risk-adopted use of potentially nephrotoxic treatment modalities and adequate counselling of patients.

Characterization of [3H]substance P binding sites in human skin

Radioligand binding experiments were performed with crude homogenates from normal human skin in order to investigate substance P receptor density. Binding of [3H]substance P ([3H]SP) reached equilibrium after 20 min and was saturable analysis of saturation curves gave a significantly better fit using two-site binding compared to the single-site model. Competition studies employing some selective agonists for NK1, NK2 and NK3 receptors have demonstrated that only the NK1 selective agonist, [Sar9, Met(O2)11]-SP, was a competitor for [3H]SP binding. In addition, the non-hydrolyzable guanosine 5'-0-(3-thiotriphosphate) altered the dissociation of SP from NK1 receptors by increasing the number of low-affinity sites. These data show that in the skin [3H]SP binds to a single population of substance P high-affinity sites, which represent NK1-type receptors.

Current role of venography in the diagnosis of deep-vein thrombosis

The clinical diagnosis of deep vein thrombosis (DVT) is barely sensitive and specific. Thus, the clinical suspicion of DVT needs to be confirmed by objective testing. Venography has been for a long time the only reliable technique to confirm or rule-out the clinical suspicion of DVT. Furthermore, venography served as "gold standard" for the validation of non-invasive diagnostic methods for DVT. Among these methods, compressive real-time B-mode ultrasonography (CUS) has substantially reduced the need of performing venography, mainly in outpatients with clinical suspicion of DVT. However, indications for venography still remain in the three DVT patient categories. CUS is highly specific in patients with a first episode of clinically suspected DVT, so that positive patients can be treated with anticoagulants without any further testing. In CUS negative patients three options are available in order to rule-out clinically significant DVT: a) to repeat CUS at day 2 and 8; b) to associate D-dimer to CUS to rule-out DVT (negative D-dimer) or to reinforce surveillance (positive D-dimer); c) to perform venography on the same day. This last approach has been proposed in patients with negative CUS and high pretest clinical probability. CUS is highly specific in high risk patients with asymptomatic DVT and thus it could be used to make treatment decision in positive patients. However, CUS is less sensitive in asymptomatic than in symptomatic patients. Thus, venography remains the only available diagnostic technique to rule-out DVT in asymptomatic patients. In clinical practice, venography should be used on individual basis. In clinical research on DVT prophylaxis, venography should be used in the assessment of the end-point. However, three recent clinical trials on the prevention of post-discharge DVT has generated some uncertainty on the clinical relevance of asymptomatic venography detected DVT. Four to six weeks after discharge a high prevalence of venography detected DVT was observed, a finding disagreeing with the low incidence of clinically overt thromboembolic events at long-term follow-up. Two strategies are available in patients with recurrent symptomatic DVT: to follow-up patients with serial impedance plethysmograph and CUS after the first episode in order to pick-up a positive test in patients previously turned negative or to perform venography, a new intraluminal filling defect suggesting DVT recurrence.

Evidence for androgen receptor gene expression and growth inhibitory effect of dihydrotestosterone on human adrenocortical cells

Evidence for the expression of the canonic androgen receptor (AR) in human adrenal cortex has not been provided so far. The aim of the present study was to demonstrate the expression of the AR gene in normal and neoplastic adrenocortical human tissues and in the human adrenocortical cancer cell line, NCI-H295, and then to evaluate the effect of dihydrotestosterone (DHT) on human adrenocortical cell growth. An AR cDNA fragment with the expected size of 262 bp was detected by using reverse transcription (RT)-PCR in normal and neoplastic adrenocortical human tissues and in the neoplastic cell line, demonstrating that the gene for AR is indeed expressed in human adrenal cells. In the human adrenocortical cancer cell line NCI-H295, DHT at physiological concentrations produced a significant reduction in cell proliferation and inhibition of colony formation in soft agar. The inhibitory effect on adrenocortical cell growth was evident after both 24 and 48 h of treatment. The antiandrogens, cyproterone acetate and hydroxyflutamide, were capable of reversing the effects exerted by DHT. The androgen-induced growth inhibitory effect was also detected in primary culture of three non-functioning adrenocortical adenomas. These findings show that the canonic AR is present in human adrenocortical cells and that androgens may have a role in the adrenal cortex by reducing cell proliferation.

Antiphospholipid syndrome, adrenal failure, dilated cardiomyopathy and chronic hepatitis: an unusual manifestation of multiorgan autoimmune injury?

The antiphospholipid syndrome is characterized by clinical evidence of arterial or venous thrombosis, thrombocytopaenia, recurrent fetal loss and repeated positivity of antiphospholipid autoantibodies. The association of antiphospholipid syndrome with the development of adrenal failure has been reported in more than 40 patients in the last 20 years, mostly due to bilateral cortical haemorrhage or thrombosis of adrenal vessels. The presence of antibodies against adrenal cortex was never documented in these patients. Here we report a case of recurrent thrombophlebitis, acute adrenal failure, and chronic hepatitis occurring in a young man found to have antiphospholipid antibodies and lupus anticoagulant. Autoantibodies against adrenal cortex were detected and abdominal ultrasonography showed morphologically normal adrenals. Mild thrombocytopaenia, Coomb's positive anaemia, increase in alanine- and aspartate-aminotransferases and increase in urinary protein excretion were found. Autoantibodies against liver/kidney microsomes were positive and liver biopsy was compatible with autoimmune hepatitis. The patient was treated with cortisone acetate, fludrocortisone and warfarin. Dilated cardiomyopathy was revealed one year later and coronarography did not document any occlusive coronary disease. Three years later, titres of autoantibodies, including those directed towards the adrenal cortex, were increased and others, previously absent, were detected. Nevertheless, the patient's clinical conditions seemed unchanged. At this time, an abdominal CT scan showed adrenal dysmorphisms with bilateral annular calcifications and central hypodensities suggesting previous bilateral adrenal haematomas. The hypercoagulable state that occurs in antiphospholipid syndrome can induce a localized inflammatory response generated by tissue injury, with a consequent release of intracellular antigens and antibodies production. Consequently, tissue-specific autoantibodies positivity may persist until the cells involved in antigen production are completely destroyed.

An Escherichia coli expression assay and screen for human immunodeficiency virus protease variants with decreased susceptibility to indinavir

We have developed a recombinant Escherichia coli screening system for the rapid detection and identification of amino acid substitutions in the human immunodeficiency virus (HIV) protease associated with decreased susceptibility to the protease inhibitor indinavir (MK-639; Merck & Co.). The assay depends upon the correct processing of a segment of the HIV-1 HXB2 gag-pol polyprotein followed by detection of HIV reverse transcriptase activity by a highly sensitive, colorimetric enzyme-linked immunosorbent assay. The highly sensitive system detects the contributions of single substitutions such as I84V, L90M, and L63P. The combination of single substitutions further decreases the sensitivity to indinavir. We constructed a library of HIV protease variant genes containing dispersed mutations and, using the E. coli recombinant system, screened for mutants with decreased indinavir sensitivity. The discovered HIV protease variants contain amino acid substitutions commonly associated with indinavir resistance in clinical isolates, including the substitutions L90M, L63P, I64V, V82A, L24I, and I54T. One substitution, W6R, is also frequently found by the screen and has not been reported elsewhere. Of a total of 12,000 isolates that were screened, 12 protease variants with decreased sensitivity to indinavir were found. The L63P substitution, which is also associated with indinavir resistance, increases the stability of the isolated protease relative to that of the native HXB2 protease. The rapidity, sensitivity, and accuracy of this screen also make it useful for screening for novel inhibitors. We have found the approach described here to be useful for the detection of amino acid substitutions in HIV protease that have been associated with drug resistance as well as for the screening of novel compounds for inhibitory activity.

Economic aspects of empiric antibiotic therapy for febrile neutropenia in children with cancer

Several antibiotic regimens have been proposed worldwide for empiric treatment of febrile neutropenia in children with cancer, but none of them shows clear advantages in terms of clinical efficacy. Therefore, other parameters, including drug acquisition costs, should be considered in the selection of treatment. Children receive a "fraction" of a standard daily dose, and this fraction is generally calculated on the basis of body weight; therefore, the cost of each day of therapy is determined by the packages available for each single drug. We calculated the acquisition costs of various drugs proposed for the empiric treatment of febrile neutropenia in children with cancer, and then we estimated the daily cost of therapy referred to different patient weights. In general, the combination regimen with ceftriaxone plus aminoglycoside turned out to be less expensive than other regimens (including monotherapy with third-generation cephalosporins or carbapenems).

Pain associated with venous ulcers in injecting drug users

Pain is a concern among people with venous ulcers. Although the prevalence is unknown, venous ulcers occur in those who have a history of illicit injecting drug use. The purpose of this study was to (a) examine the relationship between venous ulcer characteristics and pain severity, (b) ascertain factors that cause pain, (c) determine methods to alleviate pain, and (d) explore beliefs about pain medications among people with a history of injection drug use. Thirty-two patients answered pain and demographic questionnaires and had their venous ulcers traced onto plastic to identify wound area. Greater current pain, worse pain in 24 hours, and higher levels of pain relief from medications were significantly related to larger wound areas. Ibuprofen, compression dressing Unna's boot, and heroin ranked highest in decreasing pain. The most painful activities were working, walking outside, standing, and stair climbing. Many patients (41%) did not like to bother others with their complaints of pain. Participants were generally satisfied with pain treatments and the response of care providers to their pain. People who have used injected drugs and have venous ulcers do have pain. Therefore, research must continue to evaluate this pain as well as the best ways to treat it.

Distribution of indicator bacteria and bacteriophages in shellfish and shellfish-growing waters

Shellfish (mussels and clams) and shellfish-growing waters were examined for indicator bacteria according to the EC regulations, Salmonella spp., coliphages and anti-Salmonella phages. Samples were collected both from natural-growing areas along the coast and from authorized shellfish-harvesting beds. The coastal area was affected by organic pollution and extensive faecal contamination and, according to the legal requirements, was unsuitable for shellfish farming. The shellfish collected along the coast also showed faecal contamination at levels which did not conform to legal standards. No significant differences were observed between the frequency of isolation of somatic coliphages and indicator bacteria from sea water. In contrast, both the authorized and wild coastal shellfish were contaminated by coliphages at a significantly higher level than the corresponding bacterial indicators for faecal contamination (chi 2 test, P < 0.01). Coliphage concentrations were significantly correlated with faecal indicators in marine waters (P < 0.001) and sediments (P < 0.05), but no correlation was found in shellfish, thus showing their low specificity as indicators of faecal pollution of human origin in shellfish of economic importance.

Levels of adrenocortical autoantibodies correlate with the degree of adrenal dysfunction in subjects with preclinical Addison's disease

To test the hypothesis that levels of adrenal autoantibodies correlate with the degree of adrenal dysfunction, we followed up adrenal cortex autoantibody (ACA) titers and 21-hydroxylase (21OH) autoantibody (21OHAb) levels in 19 ACA-positive subjects with preclinical Addison's disease. On enrollment, all the 19 ACA-positive subjects were positive for 21OHAb. At follow-up, the concordance rate for simultaneous presence/absence of both ACA and 21OHAb was as high as 91% and a strong, positive correlation between 21OHAb levels and ACA titers was observed (P < 0.0001). The levels of adrenal autoantibodies were positively associated with the severity of adrenal dysfunction (ANOVA, P < 0.0001 for both 21OHAb and ACA): the 21OH index was significantly lower at stage 0 or 1 than at stage 2+3 (corrected P < 0.001 andP < 0.05) or stage 4 (corrected P < 0.001 and <0.01). Similarly, ACA titer at stage 4 was significantly higher than stage 0 (P < 0.001), stage 1 (P < 0.001), and stage 2+3 (P < 0.05); and ACA titer at stage 2+3 was higher than stage 0 (P < 0.001) and stage 1 (P < 0.05). In subjects with progression of adrenal dysfunction (n = 14), levels of 21OHAb and ACA increased significantly (P = 0.041 and P = 0.002) during the follow-up period. In 5 subjects, the remission of biochemical signs of adrenal dysfunction was associated with the disappearance of both ACA and 21OHAb. Our study shows that the levels of adrenal autoantibodies correlate with the degree of adrenal dysfunction, and this suggests that production of high-level 21OHAb strongly signals the destructive phase of the autoimmune disease process.

Effects of histamine H1 receptors on the feeding and drinking patterns in pygmy goats

The goal of these experiments was to determine which histamine receptors are involved in the relationship between drinking and feeding in ruminants. To this end, the effects of the histamine receptor antagonists dexbrompheniramine (H1 receptor antagonist), cimetidine (H2 receptor antagonist), and terfenadine (H1 receptor antagonist) on feeding and drinking patterns of pygmy goats were investigated. Two experiments using dexbrompheniramine [1 and 2 mg/kg of body weight (BW)0.75], two experiments using cimetidine (16 and 32 mg/kg of BW0.75), and two experiments using terfenadine (5 and 11.5 mg/kg of BW0.75) were performed to assess the type and location (periphery or central nervous system) of the histamine receptors involved in the mediation of prandial drinking by pygmy goats. The H1 receptor antagonists dexbrompheniramine (2 mg/kg of BW0.75) and terfenadine (11.5 mg/kg of BW0.75) significantly reduced water intake, but cumulative feed intake did not change. Consequently, the ratio of water intake to feed intake decreased. In contrast, the H2 receptor antagonist did not affect either water or feed intake. Dexbrompheniramine at 2 mg/kg of BW0.75 and terfenadine at 11.5 mg/kg of BW0.75 also decreased draft frequency and decreased the water intake associated with meals. Results showed that blockage of peripheral H1 histamine receptors attenuates the association between water and feed intake in pygmy goats. Therefore, the stimulating effect of feed intake on water intake appears to depend on activation of peripheral H1 histamine receptors.

Fast-reacting thiols in rat hemoglobins can intercept damaging species in erythrocytes more efficiently than glutathione

The S-conjugation rates of the free-reacting thiols present on each component of rat hemoglobin with 5,5-dithio-bis(2,2-nitrobenzoic acid) (DTNB) have been studied under a variety of conditions. On the basis of their reactivity with DTNB (0.5 mM), three classes of thiols have been defined as follows: fast reacting (fHbSH), with t1/2 <100 ms; slow reacting (sHbSH), with t1/2 30-50 s; and very slow reacting (vsHbSH), with t1/2 180-270 s. Under paraphysiological conditions, fHbSH (identified with Cys-125beta(H3)) conjugates with DTNB 100 times faster than glutathione and approximately 4000 times more rapidly than (v)sHbSH (Cys-13alpha(A11) and Cys-93beta(F9)). Such characteristics of fHbSH reactivity that are independent of the quaternary state of hemoglobin are mainly due to the following: (i) its low pK (approximately 6.9, the cysteinyl anion being stabilized by a hydrogen bond with Ser-123beta(H1)) and (ii) the large exposure to the solvent (as measured by analysis of a model of the molecular surface) and make these thiols the kinetically preferred groups in rat erythrocytes for S-conjugation. In addition, because of the high cellular concentration (8 mM, i.e. four times that of glutathione), fHbSHs are expected to intercept damaging species in erythrocytes more efficiently than glutathione, thus adding a new physiopathological role (direct involvement in cellular strategies of antioxidant defense) to cysteinyl residues in proteins.

Role of protein -SH groups in redox homeostasis--the erythrocyte as a model system

The reactivities of the sulfhydryl groups of rat, turkey, human, and calf hemoglobin were studied together with the enzyme activities of glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase, and glutaredoxin in lysed erythrocytes to evaluate their roles in regulating redox homeostasis. The results of -SH reactivity showed rate constants spanning four orders of magnitude (k2, calf, 6.67 M-1 s-1; rat -SH fast reacting, 2.8 x 10(4) M-1 s-1). Enzyme activities of glucose-6-phosphate dehydrogenase ranged from 0.402 U/ml (calf) to 0.900 U/ml (rat), glutathione reductase from 0. 162 U/ml (rat) to 0.381 U/ml (human), glutaredoxin from 0.778 U/ml (rat) to 2.28 U/ml (turkey), and glutathione peroxidase from 2.07 U/ml (human) to 27.3 U/ml (rat). Blood samples of the four species were also treated with 0.5-1.5 mM tert-butyl hydroperoxide (t-BOOH) or diamide, and levels of glutathione-derived species [GSH, GSSG, and glutathione-protein mixed disulfides (GS-SP)] were determined within 120 min and related to the corresponding protein -SH group (PSH) reactivities and enzyme repertoires. In all cases t-BOOH rapidly transformed GSH into GSSG by the action of glutathione peroxidase; GSSG was in turn transformed into GS-SP, according to the reaction GSSG + PSH --> GS-SP + GSH, or reduced back to GSH by glutathione reductase. The GSSG reduction was more efficient in rat and human blood, due to the contribution of the fast-reacting -SH of hemoglobin, in the rat, and to the efficiency of the enzyme repertoire of human blood. Calf blood showed a relatively low capacity to restore normal values after oxidative stress, due to its low PSH reactivity and the weak contribution of its enzymes. Diamide treatment, which is known to react nonenzymatically with thiols, gave increased GS-SP levels in rat and turkey, but not in human and calf blood, as expected from the different corresponding PSH reactivities. Species with relatively high PSH reactivity and glucose 6-phosphate dehydrogenase activity, such as the rat, therefore had a higher antioxidant capacity than species (calf) in which these parameters were relatively low.