The development of acute lung injury is associated with worse neurologic outcome in patients with severe traumatic brain injury

OBJECTIVE

The purpose of this study was to determine the incidence of acute lung injury (ALI) in trauma patients with severe traumatic brain injury (TBI), to evaluate the impact of ALI on mortality and neurologic outcome after severe traumatic brain injury (TBI), and to identify whether the development of ALI correlates with the severity of TBI.

METHODS

Clinical data were collected prospectively over a 4-year period in a Level I trauma center. Patients included in the study met the following criteria: mechanical ventilation > 24 hours, head Abbreviated Injury Scale score >or= 3, no other body region Abbreviated Injury Scale score >or= 3, and age between 18 and 54 years. ALI was defined using international consensus criteria. Glasgow Outcome Scale scores were assessed at 3 and 12 months. Bivariate comparisons were made between ALI and non-ALI groups. Multivariate analysis with stepwise logistical regression was used to assess independent factors on mortality. The patient's admission head computed tomographic (CT) scan was graded using the Marshall system, and the presence and size of specific intracranial abnormality was noted. Glasgow Coma Scale (GCS) score, Marshall CT scan score, and intracranial abnormality were correlated with the development of ALI.

RESULTS

One hundred thirty-seven patients with isolated head trauma were enrolled in the study over a 4-year period. Thirty-one percent of patients with severe TBI developed ALI. Head trauma patients with ALI had a significantly higher ISS, a greater number of days on the ventilator, and a worse neurologic outcome for those who survived their hospitalization. Mortality was 38% in the ALI group and 15% in the non-ALI group (p = 0.004). Only 3 of 16 (19%) of the deaths within the ALI group were directly related to ALI. By multivariate analysis, only the presence of ALI, older age, and lower initial GCS score were associated with higher mortality. There was no association between ISS, the presence of arterial hypotension (arterial systolic pressure < 90 mm Hg) at admission to the hospital, or the amount of blood transfused and mortality. No correlation was found between the severity of head injury (GCS score, Marshall score, or intracranial abnormality) and development of ALI.

CONCLUSION

The development of ALI is a critical independent factor affecting mortality in patients suffering traumatic brain injury and is associated with a worse long-term neurologic outcome in survivors. The risk of developing ALI is not associated with specific anatomic lesions diagnosed by cranial CT scanning.

The effects of tidal volume demand on work of breathing during simulated lung-protective ventilation

BACKGROUND

Lung-protective ventilation (LPV) can result in a ventilator tidal volume (V(T)) below patient V(T) demand, which may elevate work of breathing (WOB). Increasing the ventilator inspiratory flow may not sufficiently reduce WOB, because the patient's flow-time requirements may exceed the ventilator's flow-time delivery pattern. We investigated (1) the effects of V(T) demand on WOB during LPV and (2) which ventilator pattern best reduced WOB while achieving LPV goals.

METHODS

A standard WOB lung model simulated assisted breathing. Using 3 ventilators (Hamilton Veolar, Hamilton Galileo, and Dräger Evita 2 dura), we tested volume-control ventilation with a constant flow pattern (VCV-CF), volume-control ventilation with a decelerating flow (VCV-DF), and pressure-control ventilation (PCV). Simulated V(T) demand was increased from 50-125% of the ventilator-delivered V(T) (400 mL) as ventilator inspiratory time (T(I)) was decreased (0.95, 0.80, 0.65, and 0.45 s) relative to simulated T(I) (0.8 s). WOB was measured with a pulmonary mechanics monitor.

RESULTS

During VCV-CF and VCV-DF, a V(T) demand of > or = 100% drastically increased WOB, attributable to imposed WOB from the inspiratory valve. Increasing inspiratory flow by using the decelerating flow pattern and/or decreasing T(I) reduced WOB, but generally not to normal levels. "Double-triggered" breaths, with excessive V(T) delivery, often occurred when ventilator T(I) was well below simulated T(I). PCV was most effective in reducing WOB, but V(T) delivery exceeded the LPV target unless T(I) was reduced.

CONCLUSIONS

Given our dual goals of reducing both WOB and V(T) during LPV, VCV-DF with relatively brief T(I) appeared to be the best option, followed by PCV with a relatively brief T(I).

Tracheal-innominate artery fistula caused by the endotracheal tube tip: case report and investigation of a fatal complication of prolonged intubation

CASE REPORT

A patient with extensive burns was intubated with an 8.0 mm internal diameter endotracheal tube (ETT) equipped with a subglottic suction port (Mallinckrodt HiLo Evac). The ETT was secured to a left upper molar with wire sutures throughout the hospitalization course to ensure airway stability. On the 40th day of intubation, the patient exsanguinated and died from a tracheo-innominate artery fistula. Postmortem examination revealed a 1 cm lesion of the left anterior tracheal wall at the position of the ETT tip. The prolonged stationary position of the ETT was considered the primary factor responsible for the fistula. Yet tracheo-innominate artery fistula normally is associated with high cuff pressures rather than with the tube tip. The special ETT construction required for the subglottic suction feature was suspected to have increased tube rigidity and may have played a contributory role.

METHODS

The rigidity of the Mallinckrodt HiLo Evac was measured with a mechanical model and compared to 5 other commercially-available ETTs. Rigidity was expressed as the force generated by the ETT tip when the tube curvature was altered by 5 cm and 10 cm of flexion from its resting position.

RESULTS

The mean force exerted by the Mallinckrodt HiLo Evac was 10.1 +/- 2.8 g at 5 cm of flexion and 17.7 +/- 5.1 g at 10 cm of flexion. This was significantly greater than all other ETT brands tested (by one-way analysis of variance and Student-Newman-Kuels test, p < 0.05).

CONCLUSION

This case of fatal tracheo-innominate artery fistula formation associated with an ETT tip was unusual because of the extended duration of endotracheal intubation and the complexity of the patient's airway management problems. Our data suggest that the higher rigidity of the HiLo Evac ETT may have contributed to fistula development at the tube tip. However, we do not believe that the higher rigidity of the HiLo Evac ETT necessarily poses any greater risk than other ETTs under normal circumstances, in which the tube tip is not fixed in a stationary position for an extended period.

The effects of pressure control versus volume control assisted ventilation on patient work of breathing in acute lung injury and acute respiratory distress syndrome

BACKGROUND

Patient work of breathing (WOB) during assisted ventilation is reduced when inspiratory flow (V(I)) from the ventilator exceeds patient flow demand. Patients in acute respiratory failure often have unstable breathing patterns and their requirements for V(I) may change from breath to breath. Volume control ventilation (VCV) traditionally incorporates a pre-set ventilator V(I) that remains constant even under conditions of changing patient flow demand. In contrast, pressure control ventilation (PCV) incorporates a variable decelerating flow wave form with a high ventilator V(I) as inspiration commences. We compared the effects of flow patterns on assisted WOB during VCV and PCV.

METHODS

WOB was measured with a BICORE CP-100 monitor (incorporating a Campbell Diagram) in a prospective, randomized cross-over study of 18 mechanically ventilated adult patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Tidal volume, inspiratory time, and mean ventilator V(I) were constant in each mode.

RESULTS

At comparable levels of respiratory drive and minute ventilation, patient WOB was significantly lower with PCV than with VCV (0.59 +/- 0.42 J/L vs 0.70 +/- 0.58 J/L, respectively, p < 0.05). Ventilator peak V(I) was significantly higher with PCV than with VCV (103.2 +/- 22.8 L/min vs 43.8 L/min, respectively, p < 0.01).

CONCLUSIONS

In the setting of ALI and ARDS, PCV significantly reduced patient WOB relative to VCV. The decrease in patient WOB was attributed to the higher ventilator peak V(I) of PCV.

Initial severity of metabolic acidosis predicts the development of acute lung injury in severely traumatized patients

OBJECTIVES

First, to determine whether the severity of shock, as measured by systemic hypotension and metabolic acidosis, is significantly associated with a higher risk of acute lung injury in patients with severe trauma. Second, to determine whether the volumes of blood and crystalloid solutions administered in the early posttrauma period are independent risk factors for acute lung injury in severely traumatized patients.

DESIGN

Prospective observational study.

SETTING

Level I urban trauma center in a university hospital.

PATIENTS

A total of 102 severely injured, mechanically ventilated trauma patients with an Injury Severity Score > or =16 and aged between 18 and 75 yrs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Initial clinical and laboratory data were collected in the emergency department, and on a daily basis thereafter during the patient's intensive care unit stay. Of the 102 severely injured patients enrolled, 42 developed acute lung injury (41%) and 60 did not (59%). A total of 93% of the trauma patients who developed acute lung injury during the 17-month study period were included in the study. Initial base deficit was significantly lower in patients who developed acute lung injury than in those who did not (-8.8+/-4.5 vs. -5.6+/-5.1, p<.01). The difference in systolic blood pressure between the two groups was not significant.

CONCLUSIONS

In this group of severely injured trauma patients, the degree of metabolic acidosis at the time of admission identified those patients with the highest probability of developing acute lung injury. In addition, the volume of crystalloid solution administered during the first 24 hrs was significantly greater in patients who later developed acute lung injury. Finally, there was a significantly higher morbidity in patients who developed acute lung injury, whereas mortality did not differ between the two groups.

Victim-blaming tendency toward people with AIDS among college students

The victim-blaming tendency toward people with AIDS was examined in relation to gender, fraternity-sorority affiliation, classification (freshmen vs. others), religion (Catholic vs. others), and academic major (business college vs. others) in a survey of 818 students at a midwestern state university in the United States. Desired social distance from gay men and lesbians, the intervening variable in these relations, significantly mediated the indirect effect of fraternity-sorority affiliation, classification, and gender on the victim-blaming tendency. Gender and desired social distance were found to be significant direct determinants of the victim-blaming tendency toward people with AIDS. The study suggests that attitudes toward gay men and lesbians must change if attitudes toward people with AIDS are to change.

Alveolar epithelial fluid clearance persists in the presence of moderate left atrial hypertension in sheep

The effect of moderate left atrial (LA) hypertension on alveolar liquid clearance (ALC) was investigated in anesthetized, ventilated sheep, surgically prepared to measure lung lymph flow as well as hemodynamics. To simulate alveolar edema, 3-4 ml/kg of isosmolar 5% albumin in Ringer lactate were instilled into each lower lobe, and ALC was measured. After 4 h of LA hypertension (24 cmH2O), ALC was similar to that in control sheep (31 +/- 3% with LA hypertension vs. 34 +/- 10% with normal LA pressure). Because plasma epinephrine levels were moderately elevated in the presence of LA hypertension, ALC was then studied in the presence of LA hypertension following bilateral adrenalectomy. Without endogenous release of epinephrine, ALC was significantly reduced compared with normal LA pressure (20 +/- 7% compared with 34 +/- 10%, P < 0.05). Thus endogenous catecholamines caused a submaximal stimulation of ALC in the presence of LA hypertension. Exogenous administration of aerosolized beta2-agonist therapy with salmeterol increased ALC in the presence of normal LA pressure but had no stimulatory effect in the presence of moderate LA hypertension. Therefore, we tested the hypothesis that endogenous release of atrial natriuretic factor (ANF) may downregulate alveolar epithelial Na+ and fluid transport in the presence of LA hypertension. There was a modest twofold increase in plasma ANF levels after LA hypertension. Additional in vitro studies demonstrated that, in the presence of beta2-agonist stimulation, ANF decreased Na+ pump activity (Na+-K+-ATPase) in isolated rat alveolar epithelial type II cells. ANF may downregulate vectorial Na+ and fluid transport stimulated by endogenous or exogenous beta-adrenergic agonist stimulation in the presence of LA hypertension. In summary, ALC continues even in the presence of moderate LA hypertension. Aerosolized beta2-adrenergic agonist therapy significantly increased ALC, but only when LA pressure was normal.

Family caregivers: caring for aging end-stage renal disease partners

With the rapid aging of end-stage renal disease patients have come increasing burdens on families to provide care and support. This article focuses on the role changes, strains, and burdens for family caregivers, particularly spouses. Analysis is on the process of dramatic role changes and losses that occur within families and the resulting risks to dialysis patients and caregivers. Importance of constant assessment of caregivers by renal professionals is emphasized. Suggestions for families and professionals coping with role change and care burdens are offered. Concern is raised about American society shifting more care burdens onto families at a time of cultural change and stress on families, without enough societal support and programs to assist families adequately with care burdens of aging members.

Faculty Commitment: Retaining Minority Nursing Students in Majority Institutions

Minority students are at risk in majority institutions. Students face personal, academic, and institutional barriers to their success. Low retention and graduation rates at majority institutions, and particularly in nursing programs, are cause for alarm and compel nursing faculty to take action in order to reverse the trend of under-representation of minorities in the ranks of the profession. Based on the literature and personal experiences, the authors maintain that commitment of both minority and majority faculty is the primary factor in promoting minority student success. Such commitment can lead to increased involvement of faculty in the success of minority students and to the establishment of organized programs and services that facilitate minority student success. Case illustrations are included.

Predicting student success: a 10-year review using integrative review and meta-analysis

This article describes research funded by a Dean's New Investigator Award conducted to describe and evaluate nursing education research on predictors of retention, graduation, and National Council Licensure Examination success of baccalaureate-degree nursing students through an integrative review and meta-analysis of nursing research. The sample (n = 47) for the integrative review included all nursing research conducted within the years 1981 to 1990 related to predicting student success that had at least one nurse author and was published in US nursing journals or dissertations from a US university. Four studies from the corpus were appropriate to be treated meta-analytically. Ninety-four per cent of the studies were descriptive, used convenience samples, and most often identified quantitative measures, including American College Test, Scholastic Aptitude Test, and grade point average as predictor variables. Findings of the integrative review showed grade point averages in nursing and science courses as the greatest cognitive predictors of student success and parental education and age as the greatest demographic predictors. The meta-analysis portion of the study showed significant effectiveness of interventions used in the experimental studies. The Fail-Safe N (NFS) was used to assess the comprehensiveness and exhaustiveness of the literature searches. The NFS = 162 studies indicated that it would require 162 studies to overturn the conclusions.

Trauma centers in a managed care environment

Health care reform will affect the relationship of trauma centers to health maintenance organizations and other managed care plans. We studied Kaiser Permanente Medical Center (Kaiser) members admitted to the Trauma Center at San Francisco General Hospital (SFGH) to determine: (1) variables predicting transfer from SFGH to a Kaiser Hospital (repatriation), (2) the length of hospital stay (LOS), and (3) the cost of their care. The SFGH trauma registry provided data on 7,794 patients admitted before 1994. To investigate LOS, 89 Kaiser patients over 1 year were matched with non-Kaiser patients on age, maximum Abbreviated Injury Scale score (MAIS) by body region, Injury Severity Score (ISS), head injury severity, and blunt or penetrating injury and disposition. Kaiser patients were significantly younger, more likely to have blunt injury, and had a lower death rate. Significant predictors of repatriation were an MAIS score > or = 3, abdominal or extremity injury, and an ISS score of 26 to 40. The mean LOS for all Kaiser patients was 7.6 days, compared with 4.8 for controls (p = 0.20). However, mean LOS was significantly longer in repatriated Kaiser patients compared with controls (16 vs. 7.8 days, p < 0.0005). Kaiser reimbursement rates were comparable with commercial payors, but higher than others. A relatively small number of severely injured patients account for a large percentage of costly trauma care. Analyses of patient subsets are necessary for trauma centers to negotiate suitable relationships with managed care plans. A prospective study is needed to examine the cost efficiency of early transfer of managed care patients.

Identification and characterization of human neutrophil carbonic anhydrase

Many functions of polymorphonuclear leukocytes (PMNs) appear to alter and be affected by changes in the intracellular and/or extracellular acid-base milieu, suggesting that carbonic anhydrase (CA) may be important. Although small amounts of CA activity in PMNs have been reported, it has not been characterized fully. We therefore studied isolated mature circulating human PMNs and cultured HL-60 cells, an undifferentiated myelopoietic cell line, and compared these to human red cells (RBCs) for CA activity. Activity and sulfonamide inhibition were measured by a modified micromethod assay. Isoenzyme and total CA concentrations were determined by radioimmunoassay for human isozyme CA I, differential inhibition by MK-927, inhibition by 0.2% sodium dodecyl sulfate (SDS), and quantitative sulfonamide binding. Total CA activity (units/10(6) cells) was 0.04 in PMNs, 0.06 in HL-60 cells, and 0.62 in RBCs. Human PMNs have a total CA concentration of 1.3 microM, of which 0.9 microM is CA I and the remainder is CA II. Total loss of CA activity with 100 microM ethoxzolamide and 0.2% SDS ruled out significant CA III or CA IV activity. Subcellular fractionation of PMNs revealed that all CA activity was cytosolic. The absence of CA activity in mitochondrial and microsomal membrane fractions argues against any mitochondrial CA V or membrane-bound CA IV contribution to total CA activity. Neutrophils contain both CA I and II isozymes in roughly the same proportion as RBCs but at much lower concentrations, suggesting that in the course of maturation the CA content of neutrophils is regulated differently from that in erythrocytes.

Demonstration of Chlamydia trachomatis in colposcopic cervical biopsy specimens by an immunoperoxidase method

A total of 31 cervical biopsy specimens were taken from 29 women attending a genitourinary medicine clinic, nine women (11 biopsy specimens) were known to have Chlamydia trachomatis cervicitis and 20 women were known to be free of chlamydial infection. The specimens were routinely processed to paraffin wax and stained by an anti-Chlamydia immunoperoxidase technique to localise the organisms. Of the 11 positive biopsy specimens three showed positive staining of elementary/reticulate bodies. In one case the surface endocervical cells showed large inclusions which were packed with chlamydial bodies. The diagnosis of chlamydial infection is difficult to make clinically and in routine cytological and histological specimens but immunoperoxidase staining can clearly identify C trachomatis inclusions in cervical biopsy specimens provided infection is severe.

Enrichment for academic success: helping at-risk students

Successful retention of at-risk nursing students is best accomplished through an organized system that addresses their individual needs in the areas of academic, cognitive, and self-enhancement skills. The cooperative endeavors of students, faculty, and administrators in the development of one such system, Enrichment for Academic Success, has resulted in a 95% retention rate among participants. The authors describe the incentive, development, implementation, and value of the system which can be adapted to any setting with adequate human and material resources.

Role of ventilation, air filtration, and allergen production rate in determining concentrations of rat allergens in the air of animal quarters

Concentration of any substance in the air of a room is determined by the ratio between the rates of its production and removal. Thus, high concentrations can result from high production, low removal, or a combination of the two. Air filtration can supplement ventilation in removing allergens from the air. Control of aeroallergen exposure at any particular location would be more rational and effective if the contribution of production, ventilation, and filtration were known. Using immunochemical assays for rat urinary protein allergen, we measured the rate of production by individual rats and the concentration of allergens in the air of rat animal quarters where the ventilation rate was about 15 changes per hour. We introduced two different high-efficiency filtration systems that provided additional clean air changes up to a maximum of 127 changes per hour. Male rats shed about 20 ng/min of allergen. Because of this high rate of production, substantial reduction in rooms that housed large numbers of animals required the very high air-exchange rates that were achieved with laminar flow small animal isolator racks. Measured concentrations agreed well with concentrations calculated from a mass balance equation whose terms included numbers of animals in the room, production rate by individual animals, and rates of ventilation and filtration. We suggest that this principle of considering both production and removal rates applies not only to devising means of reducing levels of rat allergens in rat rooms, but generally to other indoor allergens as well.

Pertussis toxin-mediated ADP-ribosylation of rabbit luteal Gi uncouples enkephalin inhibition of adenylyl cyclase

1. Some of the actions of pertussis toxin on the rabbit luteal adenylyl cyclase system were analyzed. 2. Incubation of luteal membranes with pertussis toxin and [32P]NAD resulted in the [32P]ADP-ribosylation of a 40,000 Da protein that is distinct from the proteins ADP-ribosylated by cholera toxin. 3. Pertussis toxin specific [32P]ADP-ribosylation was time-dependent and dependent upon the concentration of pertussis toxin present during the incubation. 4. Pertussis toxin mediated [32P]ADP-ribosylation was enhanced by ATP, ADP, adenylyl imidodiphosphate, GTP, guanosine-5'-O-(2-thiodiphosphate), guanosine-5'-O-(3-thiotriphosphate), and NaF but not AMP or guanylyl imidodiphosphate [GMP-P(NH)P]. 5. Treatment of luteal membranes with NAD and pertussis toxin prevents GTP and enkephalin but not GMP-P(NH)P mediated inhibition of forskolin stimulated adenylyl cyclase, demonstrating the existence of a functional Gi in the rabbit corpus luteum.

Aeroallergens in dairy barns near Cooperstown, New York and Rochester, Minnesota

We sampled atmospheric barn air using a volumetric air sampler in ten barns near Cooperstown, NY and six barns near Rochester, MN, and, with radioimmunoassays, measured allergens of Aspergillus fumigatus, Thermoactinomyces vulgaris, Micropolyspori faeni, short ragweed, rye grass group I pollen, Alternaria (Alt-1), Dermatophagoides sp. Lepidoglyphus destructor, common insect allergen, mouse urine, rat urine, and cattle epithelium. The most abundant allergen present was A. fumigatus followed by L. destructor. This study provides initial data on barn aerobiology and demonstrates for the first time the abundance of L. destructor allergens in North American dairy barns. More comprehensive study of barns, poultry houses, confinement houses for swine, and other agricultural environments from various geographic locations is needed to define the allergen levels to which millions of farm workers are exposed each day. While most of the allergens were expected, the presence of airborne allergens reactive with antisera to Dermatophagoides suggests indirectly that substantial amounts of pyroglyphid mites are present in some barns.

Correlations between levels of mite and cat allergens in settled and airborne dust

Thirty homes in Rochester, Minn., 20 of which housed cats, were studied to compare cat and mite allergen concentrations in airborne and settled dust. With Air Sentinels in the bedroom and living room for airborne collections, and a Sample Vac for collections from living room carpet and bedroom mattress, immunochemical quantifications of each were made with various radiometric assays with polyclonal and monoclonal antibodies. The most significant correlations were found between airborne mite in the bedroom and living room (p less than 0.001) and airborne mite in the bedroom and dust from the bedroom mattress (p less than 0.001). Most houses had specific epitopes of both Dermatophagoides pteronyssinus and D. farinae, but D. farinae was present in greater amounts. In seven houses we found greater than 10 micrograms of group I mite allergen per gram of settled dust, indicating that some houses in Minnesota have concentrations of mite allergens high enough to cause allergic disease, even in the winter. Clinical interpretation of these data on air levels is hampered by uncertainty as to whether symptoms are more closely related to average steady-state exposure, which we measured, or to brief heavy concentrations. Further epidemiologic studies are needed to define the concentration of mite and cat allergens in the air that are risk factors for allergic disease. The concentration of cat allergen correlated with mite allergen in the air, but not in settled dust, presumably reflecting the fact that both are influenced by ventilation rate.

Identification of a German cockroach-specific allergen by human IgE and rabbit IgG

To further study the immunology of insect hypersensitivity, we identified and partially characterized the principal allergens in whole body German cockroach (WBGCR) (Blattella germanica) and compared this extract to whole body antigens prepared from other insects. WBGCR extract was fractionated over a calibrated Sephadex G-200 column; peak allergenic activity was contained in fraction 3 (GCR3), containing components with apparent molecular weights ranging from 12,500 to 75,000 daltons. The antigenicity, allergenicity, and specificity of GCR3 components were tested by using rabbit antisera raised to GCR3 or true armyworm (Pseudaletia unipuncta). Radioimmunoassay, cross-inhibition and immunoblot studies revealed, particularly in the IgE system, that GCR3 contained an allergen with a pI of 6.7 and MW of 36,000 daltons that was unique to WBGCR extracts and not present in other insect species, including true armyworm, caddis fly, lakefly, yellow jacket, or honeybee. This GCR3 component may represent a specific marker for the diagnosis of cockroach hypersensitivity in an insect-sensitive population of individuals.

Cholera toxin action on rabbit corpus luteum membranes: effects on adenylyl cyclase activity and adenosine diphospho-ribosylation of the stimulatory guanine nucleotide-binding regulatory component

Cholera toxin elicited 5- to 7-fold stimulation of adenylyl cyclase activity. Half-maximal activation was at 4.42 micrograms/ml cholera toxin. Cholera toxin-mediated activation was time dependent. At 0.1 mM ATP, both guanosine triphosphate (GTP) and nicotinamide adenine dinucleotide (NAD+) were required for cholera toxin activation of luteal adenylyl cyclase. The concentrations of GTP and NAD+ required for half-maximal activation were 1 and 200 microM, respectively. The GTP requirement could be eliminated by increasing the ATP concentration to 1.0 mM. Guanosine-5'-O-(2-thiodiphosphate) [GDP beta S] did not support cholera toxin activation of the luteal enzyme. Cholera toxin treatment increased GTP-stimulated activity, did not significantly alter guanyl-5'-yl imidodiphosphate [GMP-P(NH)P]-stimulated activity, and depressed NaF-stimulated activity. Furthermore, toxin treatment resulted in a 3.4-fold reduction in the Kact values for ovine luteinizing hormone (oLH) to activate adenylyl cyclase. A similar reduction in Kact values for oLH was obtained when concentration-effect curves performed in the presence of GMP-P(NH)P were compared to those performed in the presence of GTP. In addition, luteal membranes treated with cholera toxin and [32P]NAD+ were subjected to autoradiographic analysis following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This treatment resulted in the [32P] adenosine diphospho (ADP)-ribosylation of a 45,000-dalton protein doublet, corresponding to the alpha subunit of the stimulatory guanine nucleotide-binding regulatory component (Ns). As with activation of adenylyl cyclase activity, cholera toxin-specific [32P] ADP-ribosylation was time dependent and increased with increasing concentrations of cholera toxin. GTP, GMP-P(NH)P, and NaF, but not GDP beta S, were capable of supporting [32P] ADP-ribosylation of the protein doublet. oLH did not alter the ability of cholera toxin to ADP-ribosylate the protein activation of luteal adenylyl cyclase activity is due to the ADP-ribosylation of the alpha subunit of Ns and the concomitant inhibition of a GTPase associated with adenylyl cyclase.