More Active Mums in Stirling (MAMMiS): a physical activity intervention for postnatal women. Study protocol for a randomized controlled trial

Background

Many postnatal women are insufficiently physically active in the year after childbirth and could benefit from interventions to increase activity levels. However, there is limited information about the efficacy, feasibility and acceptability of motivational and behavioral interventions promoting postnatal physical activity in the UK.

Methods

The MAMMiS study is a randomized, controlled trial, conducted within a large National Health Service (NHS) region in Scotland. Up to 76 postnatal women will be recruited to test the impact of two physical activity consultations and a 10-week group pram-walking program on physical activity behavior change. The intervention uses evidence-based motivational and behavioral techniques and will be systematically evaluated using objective measures (accelerometers) at three months, with a maintenance measure taken at a six-month follow-up. Secondary health and well-being measures and psychological mediators of physical activity change are included.

Discussion

The (MAMMiS study will provide a test of a theoretical and evidence-based physical activity behavior change intervention for postnatal women and provide information to inform future intervention development and testing within this population.

Trial registration

Current Controlled Trials ISRCTN79011784

Timing of excess weight gain in the Avon Longitudinal Study of Parents and Children (ALSPAC)

OBJECTIVES

To test the hypothesis that most excess weight gain occurs by school entry in a large sample of English children, and to determine when the greatest gain in excess weight occurred between birth and 15 years.

METHODS

Longitudinal data were collected annually from birth to 15 years in 625 children. Weight and BMI at each time point were expressed relative to UK 1990 growth reference as z scores. Excess weight gain was calculated as the group increase in weight and BMI z scores between specific time periods.

RESULTS

Weight z score did not increase from birth to 5 years (mean difference: 0.04 [95% confidence interval (CI): -0.03-0.12] P = .30) but increased from 5 to 9 years (mean difference: 0.19 [95% CI: 0.14-0.23] P < .001). BMI z score increased from 7 to 9 years (mean difference: 0.22 [95% CI: 0.18-0.26] P < .001), with no evidence of a large increase before 7 years and after 9 years.

CONCLUSIONS

Our results do not support the hypothesis that most excess weight gain occurs in early childhood in contemporary English children. Excess weight gain was substantial in mid-childhood, with more gradual increases in early childhood and adolescence, which indicates that interventions to prevent excess weight should focus on school-aged children and adolescents as well as the preschool years.

Surface EMG characteristics of people with multiple sclerosis during static contractions of the knee extensors

OBJECTIVES

This study was designed to determine whether any alterations existed in surface electromyography (sEMG) in people with multiple sclerosis (MS) during isometric contractions of the knee extensors.

METHODS

Fifteen people with MS and 14 matched controls (mean ± SD age and body mass index 53·7 ± 10·5 versus 54·6 ± 9·6 years and 27·7 ± 6·1 versus 26·5 ± 4, respectively) completed 20%, 40%, 60% and 80% of their maximal voluntary contraction (MVC) of the knee extensors. sEMG was recorded from the vastus lateralis where muscle fibre conduction velocity (MFCV) and sEMG amplitude (RMS) were assessed. Body composition was determined using dual-energy X-ray absorptiometry and physical activity with the use of accelerometry.

RESULTS

People with MS showed significantly (P<0·05) faster MFCV during MVC (6·6 ± 2·7 versus 4·7 ± 1·4 m s(-1) ) and all submaximal contractions, while RMS was significantly (P<0·05) less (0·11 ± 0·03 versus 0·24 ± 0·06 mV) in comparison with the controls. MVC along with specific thigh lean mass to torque, rate of force development and mean physical activity were significantly (P<0·01) less in PwMS.

CONCLUSION

People with MS have elevated MFCV alongside reduced RMS during isometric contraction. This elevation in MFCV should be accounted for when interpreting sEMG from people with MS.

Evidence-based behavioral treatment of obesity in children and adolescents

Obesity is the most common childhood disease and is widely acknowledged as having become a global epidemic. Well-recognized health consequences of childhood obesity exist, both during childhood and adulthood, affecting health and psychological and economic welfare. The importance of finding effective strategies for the management of childhood obesity has international significance with the publication of various expert reports and evidence-based guidelines in recent years.

Randomized, controlled trial of a best-practice individualized behavioral program for treatment of childhood overweight: Scottish Childhood Overweight Treatment Trial (SCOTT)

OBJECTIVE

The objective of this study was to determine whether a generalizable best-practice individualized behavioral intervention reduced BMI z score relative to standard dietetic care among overweight children.

METHODS

The design consisted of an assessor-blinded, randomized, controlled trial involving 134 overweight children (59 boys, 75 girls; BMI > or = 98th centile relative to United Kingdom 1990 reference data for children aged 5-11 years) who were randomly assigned to a best-practice behavioral program (intervention) or standard care (control). The intervention used family-centered counseling and behavioral strategies to modify diet, physical activity, and sedentary behavior. BMI z score, weight, objectively measured physical activity and sedentary behavior, fat distribution, quality of life, and height z score were recorded at baseline and at 6 and 12 months.

RESULTS

The intervention had no significant effect relative to standard care on BMI z score from baseline to 6 months and 12 months. BMI z score decreased significantly in both groups from baseline to 6 and 12 months. For those who complied with treatment, there was a significantly smaller weight increase in those in the intervention group compared with control subjects from baseline to 6 months. There were significant between-group differences in favor of the intervention for changes in total physical activity, percentage of time spent in sedentary behavior, and light-intensity physical activity.

CONCLUSIONS

A generalizable, best-practice individualized behavioral intervention had modest benefits on objectively measured physical activity and sedentary behavior but no significant effect on BMI z score compared with standard care among overweight children. The modest magnitude of the benefits observed perhaps argues for a longer-term and more intense intervention, although such treatments may not be realistic for many health care systems.

Parents' journey through treatment for their child's obesity: a qualitative study

BACKGROUND

Treatment for childhood obesity is characterised by patient non-attendance and drop-out, and widespread failure to achieve weight maintenance. Qualitative methods may improve our understanding of patient perceptions and so improve treatment for childhood obesity.

AIM

To provide insight into the perceptions of parents of obese children as they "journey" from pre-treatment to end of treatment.

METHODS

We used purposive sampling and studied 17 parents of children (mean (SD) age 8.4 (2.1) years) attending 6-month outpatient treatments for obesity (BMI>98th percentile). Parent's perceptions were explored by in-depth interviews, analysed using Framework methods.

RESULTS

Parents were characterised as being unaware of their child's weight, in denial or actively seeking treatment. Parents were consistently motivated to enter treatment due to perceived benefits to their child's self-esteem or quality of life, and weight outcomes appeared typically less important. During treatment parents felt there was a lack of support for lifestyle changes outside the clinic, and noted that members of the extended family often undermined or failed to support lifestyle changes. Parents generally felt that treatment should have continued beyond 6 months and that it had provided benefits to their child's well-being, self-esteem and quality of life, and this is what motivated many to remain engaged with treatment.

DISCUSSION

This study may help inform future treatments for childhood obesity by providing insights into the aspects of treatment of greatest importance to parents. Future treatments may need to consider providing greater support for lifestyle changes within the extended family, and may need to focus more on psycho-social outcomes.

The B'Active programme for overweight primary school children in Glasgow: determining the prevalence of overweight and obesity and piloting an activity intervention

The aim of this study was to determine the prevalence of overweight and obesity in primary school children in Glasgow and to evaluate a pilot activity programme for overweight and obese children. BMI was measured in 1548 children. Overweight, obesity and severe obesity were defined as BMI ≥ 85th, 95th and 98th centile, respectively. Overweight and obese children were then invited to participate in a 10-week school-based activity programme. The programme was evaluated by recording weekly attendance, intensity (using the Children's Effort Rating Scale) and enjoyment (scale 1–10). Focus groups were used to explore the experiences and views of the children, teachers, coaches and parents. Of the 1548 children, 31·4 % were overweight, 19·1 % were obese and 12·4 % were severely obese; 38 % of those invited attended the activity programme. Weekly programme attendance was 83 % (range 56–99 %). Mean enjoyment rating (scale 1–10) was 8 for boys and 9 for girls. The intensity of activity sessions were rated ‘very easy’ by boys and ‘just feeling a strain’ by girls. Common themes emerging from the focus groups related to perceived positive and negative aspects of the programme (fun, concerns about stigmatising children); physical and psychological outcomes (fitter, more confident); and future recommendations (involve parents). In summary, the prevalence of overweight and obesity was high. The activity programme was successful in terms of attendance and enjoyment, and overall views of the initiative were positive and there was compelling support for its continuation.

Use of pairwise marker combination and recursive partitioning in a pharmacogenetic genome-wide scan

The objective of pharmacogenetic research is to identify a genetic marker, or a set of genetic markers, that can predict how a given person will respond to a given medicine. To search for such marker combinations that are predictive of adverse drug events, we have developed and applied two complementary methods to a pharmacogenetic study of the hypersensitivity reaction (HSR) associated with treatment with abacavir, a medicine that is used to treat HIV-infected patients. Our results show that both of these methods can be used to uncover potentially useful predictive marker combinations. The pairwise marker combination method yielded a collection of marker pairs that featured a spectrum of sensitivities and specificities. Recursive partitioning results led to the genetic delineation of multiple risk categories, including those with extremely high and extremely low risk of HSR. These methods can be readily applied in pharmacogenetic candidate gene studies as well as in genome-wide scans.

Quality of life in a clinical sample of obese children

OBJECTIVES

To measure health-related quality of life (HRQoL) in a clinical sample of obese children by child self-report and parent-proxy report; to compare quality of life assessments provided by obese children and their parents; to assess differences in quality of life between the obese clinical sample and healthy control children.

DESIGN

Pairwise comparison of obese children matched for age, gender and socio-economic status with non-obese controls.

SUBJECTS

One hundred and twenty-six obese children (body mass index (BMI) >/=98th centile) and 71 lean control children (BMI <85th centile). Controls were matched with 71 children from the obese clinical group (mean age 8.6, standard deviation (s.d.) 1.9 years; 33 M/38 F).

MEASUREMENT

The Paediatric Quality of Life Inventory (UK) version 4 was self-administered to parents and to children aged 8-12 years and interview was administered to children aged 5-7 years. This questionnaire assessed physical, social, emotional and school functioning from which total, physical and psychosocial health summary scores were derived.

RESULTS

In the obese clinical group (n=126), parent proxy-reported quality of life was low for all domains. In the obese clinical group, parent-reported scores were significantly lower than child self-reported scores in all domains except physical health and school functioning. Parent-proxy reports were significantly higher for healthy controls than obese children in all domains (median total score 85.2 vs 64.7; 95% confidence interval (CI) 15.6, 24.1). For child self-reports, only physical health was significantly higher for healthy controls than obese children (median score 81.3 vs 75.0; 95% CI 3.1, 12.5).

CONCLUSIONS

HRQoL is impaired in clinical samples of obese children compared to lean children, but the degree of impairment is likely to be greatest when assessed using the parent perspective rather than the child perspective.

Habitual physical activity and sedentary behaviour in a clinical sample of obese children

OBJECTIVE

To objectively measure habitual physical activity and sedentary behaviour in a clinical sample of obese children and to compare with age- and sex-matched non-obese controls.

DESIGN

Pairwise comparison of obese children matched for age and gender with non-obese controls.

SUBJECTS

A total of 116 obese children (body mass index (BMI)> or =98th centile) and 53 non-obese control children (BMI<85th centile). Controls were matched with 53 of the obese children (mean age 8.6, s.d. 2.0 years; 25 M and 28 F).

MEASUREMENT

Habitual physical activity and sedentary behaviour were measured over a 7-day period using CSA accelerometers. Total physical activity (mean accelerometry count per minute (c.p.m.)), percentage of monitored time in sedentary behaviour, light and moderate to vigorous intensity physical activity (MVPA) were compared.

RESULTS

Obese children (n=116) spent on average 80.4% of their monitored time in sedentary behaviour and 2.5% of their monitored time in MVPA. Total activity (mean c.p.m.) was significantly higher in the non-obese group (n=53) than the obese group (n=53), 729 vs 648 c.p.m.; 95% confidence interval (CI) 7, 155. Time spent in sedentary behaviour averaged 80.9% (s.d. 6.6) in the obese group and 79.3% (s.d. 6.2) in the non-obese group, with no significant between-group difference (95% CI -3.9, 0.6). Light intensity activity was similar in the obese and non-obese groups (15.9 vs 17.3%; 95% CI -0.3, 3.0). Participation in MVPA was significantly higher in the non-obese vs obese group (3.9 vs 2.4%; 95% CI 0.6, 2.0).

CONCLUSION

This study supports the hypothesis that a clinical sample of obese children is less physically active than non-obese children, although the difference in total activity and MVPA between the groups was small.

A randomized, controlled trial to study the effect of exercise consultation on the promotion of physical activity in people with Type 2 diabetes: a pilot study

AIM

To evaluate the effect of exercise consultation on promotion of physical activity in people with Type 2 diabetes.

METHODS

Twenty-six sedentary people with Type 2 diabetes were randomly assigned to receive an exercise consultation and standard exercise information (experimental) or standard exercise information alone (control). Exercise consultation is a one-to-one discussion, based on the transtheoretical model, designed to educate, strengthen motivation and develop realistic strategies to promote physical activity. Changes from baseline at five weeks were assessed in (a) stage of exercise behaviour (b) physical activity levels (7-day recall questionnaire and an accelerometer) (c) quality of life (SF-36 Health Survey and 22-Item Well-Being Questionnaire).

RESULTS

82% (9/11) of participants receiving a consultation increased their stage of exercise behaviour compared to 33% (4/12) of controls (chi2 = 5.4, P = 0.02). Physical activity counts/week increased by 4% (1636 067/1696 191) in the experimental group and decreased by 9% (1560 960/1725 510) in controls. A significant difference was recorded for the change in activity counts per week from baseline to follow-up between the experimental and control group (98% CI = 60 673-710 827). The number of participants taking part in sport or leisure activity increased by 55% (6/11) in the experimental group and decreased by 6% (1/12) in controls. Positive changes were evident in the experimental group, compared to controls, in both quality of life questionnaires.

CONCLUSION

Exercise consultation is more effective in stimulating exercise behaviour change in the short term than a standard exercise leaflet.

Evaluation of sexual functioning in depressed outpatients: a double-blind comparison of sustained-release bupropion and sertraline treatment

Sexual dysfunction is a frequently reported side effect of many antidepressants, including serotonin reuptake inhibitors. Bupropion, an antidepressant of the aminoketone class, is relatively free of adverse sexual effects. In a randomized, double-blind, multicenter trial, sustained-release bupropion (bupropion SR) and sertraline, a selective serotonin reuptake inhibitor, were found to be similarly efficacious in the treatment of outpatients with moderate to severe depression. This report describes the results of a double-blind comparison of the sexual side effect profiles of bupropion SR and sertraline. Two hundred forty-eight patients who had received a diagnosis of moderate to severe major depression were randomly assigned to receive treatment with bupropion SR (100-300 mg/day) or sertraline (50-200 mg/day) for 16 weeks. Eligible patients were required to be in a stable relationship and to have normal sexual functioning. Sexual functioning was assessed by the investigator at each clinic visit using investigator-rated structured interviews. A significantly greater percentage of sertraline-treated patients (63% and 41% of men and women, respectively) developed sexual dysfunction compared with bupropion SR-treated patients (15% and 7%, respectively). Sexual dysfunction was noted as early as day 7 in sertraline-treated patients at a dose of 50 mg/day and persisted until the end of the 16-week treatment phase. Four patients, all of whom were treated with sertraline, discontinued from the study prematurely because of sexual dysfunction. Given the similar efficacy of the two drugs in treating depression, bupropion SR may be a more appropriate antidepressant choice than sertraline in patients for whom sexual dysfunction is a concern.

A controlled trial of sustained-release bupropion, a nicotine patch, or both for smoking cessation

BACKGROUND AND METHODS

Use of nicotine-replacement therapies and the antidepressant bupropion helps people stop smoking. We conducted a double-blind, placebo-controlled comparison of sustained-release bupropion (244 subjects), a nicotine patch (244 subjects), bupropion and a nicotine patch (245 subjects), and placebo (160 subjects) for smoking cessation. Smokers with clinical depression were excluded. Treatment consisted of nine weeks of bupropion (150 mg a day for the first three days, and then 150 mg twice daily) or placebo, as well as eight weeks of nicotine-patch therapy (21 mg per day during weeks 2 through 7, 14 mg per day during week 8, and 7 mg per day during week 9) or placebo. The target day for quitting smoking was usually day 8.

RESULTS

The abstinence rates at 12 months were 15.6 percent in the placebo group, as compared with 16.4 percent in the nicotine-patch group, 30.3 percent in the bupropion group (P<0.001), and 35.5 percent in the group given bupropion and the nicotine patch (P<0.001). By week 7, subjects in the placebo group had gained an average of 2.1 kg, as compared with a gain of 1.6 kg in the nicotine-patch group, a gain of 1.7 kg in the bupropion group, and a gain of 1.1 kg in the combined-treatment group (P<0.05). Weight gain at seven weeks was significantly less in the combined-treatment group than in the bupropion group and the placebo group (P<0.05 for both comparisons). A total of 311 subjects (34.8 percent) discontinued one or both medications. Seventy-nine subjects stopped treatment because of adverse events: 6 in the placebo group (3.8 percent), 16 in the nicotine-patch group (6.6 percent), 29 in the bupropion group (11.9 percent), and 28 in the combined-treatment group (11.4 percent). The most common adverse events were insomnia and headache.

CONCLUSIONS

Treatment with sustained-release bupropion alone or in combination with a nicotine patch resulted in significantly higher long-term rates of smoking cessation than use of either the nicotine patch alone or placebo. Abstinence rates were higher with combination therapy than with bupropion alone, but the difference was not statistically significant.

Double-blind comparison of bupropion sustained release and sertraline in depressed outpatients

BACKGROUND

A sustained-release formulation of bupropion (bupropion SR), developed with an improved pharmacokinetic profile to permit less frequent dosing than the immediate-release form, has not been evaluated in active comparator trials. This randomized, double-blind, parallel-group trial was conducted to compare the efficacy and safety of bupropion SR and sertraline.

METHOD

Outpatients with moderate to severe major depressive disorder (DSM-IV) received bupropion SR (100-300 mg/day) or sertraline (50-200 mg/day) for 16 weeks. Psychiatric evaluations, including the Hamilton Rating Scale for Depression (HAM-D), the Hamilton Rating Scale for Anxiety (HAM-A), the Clinical Global Impressions scale for Severity of Illness (CGI-S), and for Improvement (CGI-I) were completed, and adverse events were assessed in the clinic periodically throughout treatment. Patients' orgasm function was also assessed.

RESULTS

Mean HAM-D, HAM-A, CGI-I, and CGI-S scores improved over the course of treatment in both the bupropion SR group and the sertraline group; no between-group differences were observed on any of the scales. Orgasm dysfunction was significantly (p < .001) more common in sertraline-treated patients compared with bupropion SR-treated patients. The adverse events of nausea, diarrhea, somnolence, and sweating were also experienced more frequently (p < .05) in sertraline-treated patients. No differences were noted between the two treatments for vital signs and weight.

CONCLUSION

This double-blind comparison of bupropion SR and sertraline demonstrates that bupropion and sertraline are similarly effective for the treatment of depression. Both compounds were relatively well tolerated, and orgasm dysfunction, nausea, diarrhea, somnolence, and sweating were reported more frequently in sertraline-treated patients.

Surface potentials generated by synchronous activation of different fractions of the motor pool

Surface electromyogram potentials were recorded from the abductor pollicis brevis, abductor digiti minimi, and extensor digitorum brevis muscles in response to finely graded nerve stimuli. Successive potentials were subtracted to obtain intermediate potentials 2%, 5%, 10%, 20%, and 50% of the maximal compound muscle action potential (mCMAP). The average latency of the onset and negative and positive peaks, and the average duration of the negative phase and whole potential were similar for all degrees of fractionation, although smaller fractionation was associated with increasing variability. An initial positivity occurred with some of the smaller fractions of the CMAP, particularly those with the lowest stimulus threshold. Submaximal CMAPs closely resembled the mCMAP once their amplitude was greater than 5-10% of the mCMAP. Our results support the common practice of expressing H-reflex amplitudes as a percentage of the M wave and may partly explain why reflexes "scale" in response to tonic activation.

Mice lacking progesterone receptor exhibit pleiotropic reproductive abnormalities

Although progesterone has been recognized as essential for the establishment and maintenance of pregnancy, this steroid hormone has been recently implicated to have a functional role in a number of other reproductive events. The physiological effects of progesterone are mediated by the progesterone receptor (PR), a member of the nuclear receptor superfamily of transcription factors. In most cases the PR is induced by estrogen, implying that many of the in vivo effects attributed to progesterone could also be the result of concomitantly administered estrogen. Therefore, to clearly define those physiological events that are specifically attributable to progesterone in vivo, we have generated a mouse model carrying a null mutation of the PR gene using embryonic stem cell/gene targeting techniques. Male and female embryos homozygous for the PR mutation developed normally to adulthood. However, the adult female PR mutant displayed significant defects in all reproductive tissues. These included an inability to ovulate, uterine hyperplasia and inflammation, severely limited mammary gland development, and an inability to exhibit sexual behavior. Collectively, these results provide direct support for progesterone's role as a pleiotropic coordinator of diverse reproductive events that together ensure species survival.

Improvement in fluoxetine-associated sexual dysfunction in patients switched to bupropion

BACKGROUND

This study was conducted to determine the effect of bupropion on the sexual functioning of male and female outpatients who developed anorgasmia or delayed orgasm while receiving fluoxetine treatment for depression.

METHOD

Thirty-nine patients who satisfied criteria for participation in the study discontinued fluoxetine treatment and entered a 2-week washout phase followed by an open 8-week bupropion treatment phase. Three parameters of sexual functioning were followed throughout the study: orgasm function, libido, and satisfaction with overall sexual functioning. Depression was also evaluated at each visit.

RESULTS

All patients reported orgasm delay and/or failure at the time of fluoxetine discontinuation. Orgasm function, libido, and satisfaction with sexual functioning improved during the 2-week fluoxetine washout period and during the bupropion treatment phase. Ninety-four percent of patients (29/31) had complete or partial resolution of their orgasm dysfunction at the end of bupropion treatment, and 81% of patients (25/31) were "much" or "very much" more satisfied with their overall sexual functioning. Most patients entered the study with decreased libido on fluoxetine. Libido was "much" or "very much" increased for 81% of patients (25/31) at the end of the study. In addition, depression scores on the Hamilton Rating Scale for Depression and Clinical Global Impressions-Severity scale significantly improved during the bupropion treatment phase. Finally, bupropion was well tolerated by most patients.

CONCLUSION

Bupropion may be an appropriate antidepressant for patients who develop sexual dysfunction during fluoxetine treatment or for whom sexual dysfunction is a concern.

Diethylstilbestrol stimulates persistent phosphatidylinositol lipid turnover by an estrogen receptor-mediated mechanism in immature mouse uterus

The effect of estrogen on phosphoinositide (PI) metabolism was evaluated in the immature mouse uterus, a tissue which undergoes estrogen-induced proliferation. Uteri isolated from untreated mice or from mice injected ip with diethylstilbestrol (DES) were incubated with [3H]myo-inositol and assessed for incorporation of label into PI lipids or inositol phosphate generation. DES administration elicited a rapid increase in [3H]myo-inositol incorporation, which persisted until at least 18 h post treatment. This effect could not be duplicated by incubation of uteri with DES in vitro, although [3H]myo-inositol incorporation in uteri removed from DES-treated mice remained elevated for 3 h of in vitro incubation. Stimulation of PI lipid metabolism by DES was blocked by ICI 164,384, a specific estrogen receptor antagonist. The effect of DES on PI metabolism consisted of a time-dependent increase in the specific activity of both phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-bisphosphate and a significant increase of inositol (1,4,5)-trisphosphate mass by 12 h post treatment. These changes occur before the onset of estrogen-induced DNA synthesis. The results indicate that estrogens rapidly modulate PI lipid turnover through an estrogen receptor-mediated mechanism. Since the metabolic products of PI lipids are important for signal transduction and cellular proliferation, altered metabolism of these lipids may play an integral role in estrogen-induced mitogenesis.

Role of inositol (1,4,5)trisphosphate in epidermal growth factor-induced Ca2+ signaling in A431 cells

The effects of epidermal growth factor on Ca2+ signaling in A431 cells were investigated. Epidermal growth factor induced a transient Ca2+ signal in the absence of external Ca2+ and a sustained response in the presence of extracellular Ca2+, indicating an ability to mobilize intracellular Ca2+ as well as the ability to increase Ca2+ entry from the extracellular space. The Ca(2+)-ATPase inhibitor thapsigargin also activated Ca2+ entry, and neither epidermal growth factor nor the guanine nucleotide-dependent protein-linked receptor agonist bradykinin activated additional Ca2+ entry over that due to thapsigargin. In nominally Ca(2+)-free medium, the addition of bradykinin to A431 cells rapidly but transiently increased inositol 1,4,5-trisphosphate and, in parallel fashion, transiently increased cytosolic Ca2+. Unexpectedly, under these experimental conditions, epidermal growth factor elicited a small but significant Ca2+ signal after the addition of bradykinin. Experiments were designed to determine whether the Ca2+ response to epidermal growth factor after bradykinin results from mobilization of Ca2+ by an inositol 1,4,5-trisphosphate-independent mechanism. Epidermal growth factor stimulated additional inositol 1,4,5-trisphosphate formation in bradykinin-treated cells. Furthermore, the Ca2+ signals elicited by both bradykinin and epidermal growth factor were blocked in cells microinjected with the inositol 1,4,5-trisphosphate receptor antagonist heparin, whereas the intracellular Ca(2+)-ATPase inhibitor thapsigargin still mobilized Ca2+. Finally, histamine, a less efficacious guanine nucleotide-dependent protein-linked receptor agonist, as well as photolyzed, microinjected, caged inositol 1,4,5-trisphosphate, also mobilized Ca2+ after bradykinin. The results of this study show (i) that epidermal growth factor activates intracellular Ca2+ release as well as Ca2+ entry, the latter most likely resulting from an indirect effect due to the depletion of intracellular Ca2+ pools, (ii) that the actions of epidermal growth factor on Ca2+ homeostasis can be fully accounted for by inositol 1,4,5-trisphosphate formation, and (iii) that the ability of A431 cells to produce Ca2+ signals when epidermal growth factor is applied after bradykinin can be explained by the rapid and complete desensitization of the bradykinin stimulated phospholipase C activity.