The role of motivation on physical activity and screen time behaviors among parent-adolescent dyads: The FLASHE study.

Behavioral theories inform the development of lifestyle interventions to address low participation in physical activity (PA); however, relatively little is known about the value of self-determination theory (SDT) for explaining screen time (ST) behaviors or in extending SDT into a dyadic context. Actor-partner (i.e., parent-adolescent) interdependence models (APIMs) allow for examination of these interpersonal relationships. The purpose of this study was to examine PA and ST among parent-adolescent dyads using the cross-sectional Family Life, Activity, Sun, Health, and Eating (FLASHE) Study. Parent-adolescent dyads provided responses to online surveys addressing PA (n = 1177 dyads) and ST (n = 1489 dyads) behaviors. We examined the influence of SDT-based constructs (perceived competence and motivation) on PA and ST behaviors. Structural equations were used to estimate APIMs in STATA 15.1. Full models provided a good fit to the data. For both PA and ST, perceived competence was more strongly associated with motivation among adolescents compared with parents (PA: ß = 0.72 vs. 0.58, ST: ß = 0.34 vs. 0.22, p's < 0.001). Parental motivation was associated with parental PA and both adolescent motivation for PA and ST (p's < 0.001). Parental motivation was not associated with adolescent ST-behavior. Adolescent motivation was only associated with parent motivation for PA. In the FLASHE study, SDT constructs extend acceptably to the dyadic setting, with PA models providing a slightly better fit to the data than ST models. Longitudinal studies that target perceived competence and the self-regulation of motivation in parents and their adolescents are a next logical step to understanding both PA and ST behaviors.

The effect of supplementation with alkaline potassium salts on bone metabolism: a meta-analysis.

UNLABELLED: The role of acid-base metabolism in bone health is controversial. In this meta-analysis, potassium bicarbonate and potassium citrate lowered urinary calcium and acid excretion and reduced the excretion of the bone resorption marker NTX. These salts may thus be beneficial to bone health by conserving bone mineral. INTRODUCTION: The role of acid-base homeostasis as a determinant of bone health and the contribution of supplemental alkali in promoting skeletal integrity remain a subject of debate. The objective of this study was, therefore, to conduct a meta-analysis to assess the effects of supplemental potassium bicarbonate (KHCO3) and potassium citrate (KCitr) on urinary calcium and acid excretion, markers of bone turnover and bone mineral density (BMD) and to compare their effects with that of potassium chloride (KCl). METHODS: A total of 14 studies of the effect of alkaline potassium salts on calcium metabolism and bone health, identified by a systematic literature search, were analysed with Review Manager (Version 5; The Cochrane Collaboration) using a random-effects model. Authors were contacted to provide missing data as required. Results are presented as the standardised (SMD) or unstandardized mean difference (MD) (95 % confidence intervals). RESULTS: Urinary calcium excretion was lowered by intervention with both KHCO3 (P = 0.04) and KCitr (P = 0.01), as was net acid excretion (NAE) (P = 0.002 for KHCO3 and P = 0.0008 for KCitr). Both salts significantly lowered the bone resorption marker NTX (P < 0.00001). There was no effect on bone formation markers or BMD. KHCO3 and KCitr lowered calcium excretion to a greater extent than did KCl. CONCLUSIONS: This meta-analysis confirms that supplementation with alkaline potassium salts leads to significant reduction in renal calcium excretion and acid excretion, compatible with the concept of increased buffering of hydrogen ions by raised circulating bicarbonate. The observed reduction in bone resorption indicates a potential benefit to bone health.

Changes in Physical Activity and Television Viewing From Pre-pregnancy Through Postpartum Among a Socioeconomically Disadvantaged Perinatal Adolescent Population.

STUDY OBJECTIVE: Adolescent pregnancy contributes to accelerated trajectories of adiposity and cardiometabolic diseases. Two potentially low-cost prevention strategies include promoting physical activity (PA) and limiting television (TV) viewing. Few studies have explored these behavior patterns in perinatal adolescents. This study sought to characterize PA and TV viewing in a socioeconomically disadvantaged perinatal adolescent population. DESIGN, SETTING, PARTICIPANTS, AND INTERVENTIONS: A cross-sectional, retrospective, 10-item survey was used to explore behavior patterns in 79 predominantly Black (86%) postpartum adolescents. MAIN OUTCOME MEASURES: Outcomes included self-reported changes in PA from pre-pregnancy through pregnancy, and 7-day recall of PA and TV viewing in postpartum. RESULTS: The majority of adolescents (66%) reported being active on ≥3 days/week in pre-pregnancy; however, many reported low PA (≤2 days/wk) in their first (59%), second (66%), and third (54%) trimesters. Adolescents who reported being active on ≥5 days/wk in pre-pregnancy (19%) experienced first trimester PA decline, which subsequently plateaued. This group remained the most active throughout pregnancy. In postpartum, over half (54%) of all adolescents reported low PA and irrespective of PA, spent considerable time watching TV (median = 1680.0 minutes, inerquartile range = 2940). CONCLUSION: Interventions promoting PA coupled with reducing TV viewing during pregnancy and in postpartum may benefit perinatal adolescents. The findings from this study suggest that PA history is a predictor of gestational PA, and low PA and high TV viewing in postpartum underscore the need for behavioral intervention. Conducting a brief assessment of PA history in early gestation may offer important insight.

Implementation of a Community Walking Program (Walk On!) for Functionally-Limited Older Adults.

BACKGROUND: Walking interventions improve physical function, reduce fall risk, and prevent mobility disability-even in those with compromised walking ability. However, most prior studies have been conducted in controlled research settings, with no dissemination of an evidence-based walking program for older adults who have mobility limitations and/or are socially isolated. OBJECTIVES: This study reports data on the feasibility and acceptability of a community-based walking program (Walk On!) for older adults who are functionally limited, and assesses changes in physical function among attendees. The program sessions focused on long-distance walking, and took place for one-hour, for two days/week, and for 12 weeks at a time. DESIGN: Pilot implementation study. SETTING: Local church in Winston-Salem, NC. PARTICIPANTS: 49 program participants; Measurements: Physical function battery and satisfaction survey data, as well as formative evaluation data from six attendees of a focus group, are reported. RESULTS: The majority of the participants were >75 years (71%), female (65%), and presented with low levels of physical function (usual gait speed=0.79±0.16; 30.6% used an assistive device). Satisfaction with the program was high (100% would recommend it to others) and focus group results were overwhelmingly positive. Mean attendance to scheduled sessions was 77%±21%, and 63% of participants attended at least 75% of scheduled sessions (n=8 attended 100%). On average, participants improved their 6-min walk distance by 8.9%, their SPPB score by 15.4%, their timed-up-go time by 9.0%, and their usual gait speed by 11.4%. CONCLUSION: The results of the initial evaluation of Walk On! show high feasibility and acceptability of the program, as well as efficacy for improving physical function. Further research is needed to evaluate a delivery method for wider implementation of the program and to definitively test its effectiveness for improving function and other health benefits.

The impact of summer programming on the obesogenic behaviors of children: behavioral outcomes from a quasi-experimental pilot trial.

BACKGROUND: Children from low-income families experience accelerated BMI gain and learning loss during summer. Healthy Summer Learners (HSL) addresses accelerated BMI gain and academic learning loss during summer by providing academic- and health-focused programming. This manuscript reports the effects of HSL on underlying obesogenic behaviors (i.e., physical activity, screen time, sleep, diet) that lead to accelerated summer BMI gain, a necessary first step to informing a future randomized controlled trial of HSL. METHODS: In the summer of 2018 and 2019 using a quasi-experimental study design, 180 children (90 per summer, 7.9 years [SD = 1.0], 94% non-Hispanic Black, 40% male) at two schools (i.e., one per summer) who were struggling academically (25-75% on a standardized reading test) were provided a free, school-based 6-week health- and academic-focused summer program (i.e., HSL, n = 60), a 4- to 6-week academic-focused summer program (i.e., 21st Century Summer Learning program (21C), n = 60), or no summer program (n = 60). Children wore the Fitbit Charge 2™ over a 10-week period during the summers (June-Aug) of 2018-2019. Differences within (within child days attend vs. not attend) and between (differences between groups attend vs. not attend) were evaluated using mixed effects linear regression. RESULTS: Regression estimates indicated that, on days attending, HSL children experienced a greater reduction in sedentary minutes (- 58.6 [95% CI = - 92.7, - 24.4]) and a greater increase in moderate-to-vigorous physical activity (MVPA) (36.2 [95% CI = 25.1, 47.3]) and steps (2799.2 [95% CI = 2114.2, 3484.2]) compared to 21C children. However, both HSL and 21C children were more active (i.e., greater MVPA, total steps) and less sedentary (i.e., less sedentary minutes and total screen time) and displayed better sleeping patterns (i.e., earlier and less variability in sleep onset and offset) on days they attended than children in the control. CONCLUSIONS: HSL produced greater changes in physical activity than 21C. However, attendance at either HSL or 21C leads to more healthy obesogenic behaviors. Based on the behavioral data in this pilot study, a larger trial may be warranted. These results must be considered along with the pending primary outcomes (i.e., academics and BMI z-score) of the HSL pilot to determine if a full-scale trial is warranted. TRIAL REGISTRATION: NIH-NCT03321071. Registered 25 October 2017.

Physical activity and family-based obesity treatment: a review of expert recommendations on physical activity in youth.

Targeting physical inactivity in children is pertinent to aiding in the decrease of childhood obesity rates. Only 33% of adolescents are obtaining the recommended goal of at least 60 min of physical activity per day. The objectives of this review are to summarize professional recommendations for physical activity and exercise in children and adolescents, and identify family-centred strategies that can be implemented by weight management clinicians. Clinically oriented recommendations and policy statements from professional organizations were identified through literature and internet searches, summarized using rubrics of aerobic, muscle strengthening and bone strengthening exercise, then examined for details on family-based focus, inclusion of child developmental stage and age, and application to the prevention and treatment of obesity. Current recommendations give guidelines for the amount of physical activity that children should acquire and how many days a week activities should occur. However, available guidelines need an improved approach to addressing the role of the parents and caregivers in targeting physical activity and weight management in youth. Efforts must be taken in order to make sure that the types of physical activity offered are both suitable and enjoyable. Sports, games, free play and other age appropriate activities are adequate ways to increase moderate to vigorous physical activity in children. Differentiating physical activities types in accordance with developmental stage, level of enjoyment, and family characteristics is needed to establish sustainable habits. One paediatric obesity program has developed approaches to teaching families fun and engaging ways to be active together.

Vitamin D status and associated genetic polymorphisms in a cohort of UK children with non-alcoholic fatty liver disease.

BACKGROUND: Vitamin D deficiency has been associated with non-alcoholic fatty liver disease (NAFLD). However, the role of polymorphisms determining vitamin D status remains unknown. OBJECTIVES: The objectives of this study were to determine in UK children with biopsy-proven NAFLD (i) their vitamin D status throughout a 12-month period and (ii) interactions between key vitamin D-related genetic variants (nicotinamide adenine dinucleotide synthase-1/dehydrocholesterol reductase-7, vitamin D receptor, group-specific component, CYP2R1) and disease severity. METHODS: In 103 paediatric patients with NAFLD, serum 25-hydroxyvitamin D (25OHD) levels and genotypes were determined contemporaneously to liver biopsy and examined in relation to NAFLD activity score and fibrosis stage. RESULTS: Only 19.2% of children had adequate vitamin D status; most had mean 25OHD levels considered deficient (<25 nmol·L-1 , 25.5%) or insufficient (<50 nmol·L-1 , 55.3%). Patients had significantly lower 25OHD levels in winter months (95% CI: 22.7-31.2 nmol·L-1 ) when compared with spring (30.5-42.1 nmol·L-1 ; P = 0.0089), summer (36.3-47.2 nmol·L-1 ; P < 0.0001) and autumn (34.2-47.5 nmol·L-1 ; P = 0.0003). Polymorphisms in the nicotinamide adenine dinucleotide synthase-1/dehydrocholesterol reductase-7 (rs3829251, rs12785878) and vitamin D receptor (rs2228570) genes were independently associated with increased steatosis; while a group-specific component variant (rs4588) was associated with increased inflammation in liver biopsies. CONCLUSIONS: Children with NAFLD in the UK have particularly low winter vitamin D status, with vitamin D insufficiency prevalent throughout the year. Polymorphisms in the vitamin D metabolic pathway are associated with histological severity of paediatric NAFLD.

Effects of reserpine, epidermal growth factor, and cyclic nucleotide modulators on epidermal mitosis.

The mouse ear G2 mitosis assay was modified for the screening of potential antimitotic agents. An inhibitory adrenergic influence, which maintains mitotic rate at a normally low level, was removed by pretreatment of mice with reserpine. This depletes endogenous catecholamines, produces a state of enhanced mitotic activity, and makes the epidermal cells particularly sensitive to mitotic inhibition by agents which elevate the levels of cyclic AMP. Isoproterenol [IC 50 approximately 1 X 10(-9) M], prostaglandins, dibutyryl cyclic AMP [IC 50 approximately 2 X 10(-5) M], papaverine, theophylline and 5' AMP were inhibitory in the assay, whereas dibutyryl cyclic GMP and the cholinergic stimulator carbamylcholine either stimulated or had no effect on mitosis. Epidermal growth factor was employed as an alternate means of stimulating cell division. Skin fron newborn mice or rats pretreated with this substance had increased epidermal mitotic activity which was inhibited cyclic AMP elevators.

Identification and sequencing of the Thermotoga maritima lacZ gene, part of a divergently transcribed operon.

The lacZ gene encoding a beta-galactosidase (beta Gal) from the hyperthermophile Thermotoga maritima was cloned on an 11-kb fragment by complementation of an Escherichia coli lacZ deletion stain. The nucleotide sequence of the structural gene and two other ORFs found within a 6317-bp region were determined. The deduced amino acid (aa) sequence of the Tt. maritima beta Gal predicts a 1037-aa polypeptide with a calculated M(r) of 122,312. The translated sequence is 30% similar to nine other beta Gal sequences from bacteria and one yeast. Alignment of the Tt. maritima beta Gal with these other sequences reveals that the residues responsible for Mg2+ binding, catalysis and substrate recognition are conserved in the thermophilic enzyme. Sequence analysis also revealed the presence of a divergently transcribed operon containing at least two other genes 5' to lacZ. These ORFs encode proteins homologous to a second family of beta Gal found in Bacillus species and to an ATP-dependent family of bacterial oligopeptide transport proteins.

Insertional mutagenesis by a modified in vitro Ty1 transposition system.

Transposable elements are useful tools for insertional mutagenesis and have many potential applications in the characterization of complex genomes. Here we describe a system which facilitates the construction of large transposon insertion libraries useful for genome sequencing and functional genomic analysis. We developed two transposons, TyK and TyK'GFP+, which can be introduced into target DNAs by Ty1-mediated transposition in vitro, and several modifications which decrease the frequency of false transposition events and direct the recovery of transpositions into passenger rather than vector DNA. Insertions of TyK'GFP+ additionally may yield fusions to the Aequorea green fluorescent protein (GFP), useful in studies of gene expression and protein targeting. Transposition in vitro was obtained into target DNAs of up to 50 kb in size, restriction mapping showed insertion to be relatively random, and the sequence of 55 insertion sites showed neither strong site nor base compositional preference. Our data suggest that TyK-based artificial transposons will be suitable for a variety of genetic applications in many organisms.

Magnetic resonance imaging and neurobehavioral correlates in schizencephaly.

We studied three patients with schizencephaly and related the results of comprehensive neuropsychologic and speech/language assessments to the severity and location of the brain malformations as appreciated by magnetic resonance imaging. Level of general intellectual functioning related to the amount of brain tissue involved, and variations in specific neurobehavioral abilities reflected the location of the brain malformation and the prenatal onset of the disorder. The overall findings emphasize the importance of comprehensive neuropsychologic and speech/language studies for appreciating the impact of prenatal neural insult on the functional reorganization of the brain and subsequent neurobehavioral functioning.

Heteroatom analogues of bemoradan: chemistry and cardiotonic activity of 1,4-benzothiazinylpyridazinones.

A series of close analogues of the potent, long-acting cardiotonic bemoradan (2a) was synthesized and examined in both in vitro and in vivo test systems. Changing the oxygen heteroatom at the 1-position of the benzoxazine ring of bemoradan to sulfur gave 4a, a more potent enzyme inhibitor and in vivo cardiotonic compound by the iv route. Intraduodenal administration of bemoradan, however, showed a superior response compared to its sulfur analogue, possibly due to oxidation of sulfur followed by a facile Pummerer rearrangement. Model studies were performed to examine the effect of the oxidation state of sulfur. Lack of a heteroatom at the 1-position, 3a (Y-590), afforded a compound with activity and potency very similar to those of bemoradan while the 1-selena compound gave a much less potent analogue 5. Analogues having a methyl group on the 4-nitrogen (2b, 3b, and 4b) were less potent than the desmethyl compounds, but all of these compounds have potent PDE III inhibiting activity and the ability to increase cardiac force in an anesthetized dog preparation when given iv.

Synthesis of (aryloxy)alkylamines. 2. Novel imidazo-fused heterocycles with calcium channel blocking and local anesthetic activity.

A series of imidazo-fused heterocycles substituted with an aryloxy)alkylamine side chain were prepared as modifications to butoprozine (I) and found to possess calcium channel blocking activity similar in potency to that of bepridil in trachea smooth muscle and similar to that of verapamil in nitrendipine binding affinity in rabbit cardiac muscle. Of the various imidazo-fused heterocycles prepared, the imidazo[1,2-a]pyridines were also found to be potent local anesthetic agents. While most compounds in this series were equipotent to lidocaine in our initial screen, compounds 2 and 35 showed local anesthetic activity approximately 100 times more potent than lidocaine in our preliminary assays. These compounds represent a novel structural class of local anesthetic agents, and compound 2 is under further investigation.

Cardiotonic agents. Synthesis and inotropic activity of a series of isoquinolin-3-ol derivatives.

A series of isoquinolin-3-ol derivatives (II) was prepared as analogues of the clinical cardiotonic agent bemarinone (ORF 16600, I). Although in many respects the structural requirements for the cardiotonic activity of II are similar to those of bemarinone, certain differences between the series were noted. Our structure-activity studies show that II is less sensitive to alkoxy-substitution effects than is I, and more significantly, 4-substitution of II by alkyl groups, halogen, or alkanecarboxylic acid derivatives enhances cardiotonic activity in II in contrast to I, wherein analogous substitution eliminated activity. A linear correlation between contractile force (CF) increase and cyclic nucleotide phosphodiesterase fraction III (PDE-III) inhibition by the title compounds was determined. The isoquinoline derivatives were characteristically short-acting cardiotonic agents with good potency and selectivity.

6-Benzoxazinylpyridazin-3-ones: potent, long-acting positive inotrope and peripheral vasodilator agents.

A series of 6-benzoxazinylpyridazin-3-ones was prepared and evaluated for inhibition of cardiac phosphodiesterase (PDE) fraction III in vitro and for positive inotropic activity in vivo. 6-[3,4-Dihydro-3-oxo-1,4(2H)-benzoxazin-7-yl]-2,3,4,5-tetrahydro-5 - methylpyridazin-3-one (bemoradan) was found to be an extremely potent and selective inhibitor of canine PDE fraction III and a long-acting, potent, orally active inotropic vasodilator agent in various canine models. Additional benzoxazin-6-yl and -8-yl compounds were also prepared. Altering the pyridazinone substitution from the 6-position to the 7-position produced a 14-fold increase in the iv cardiotonic potency (ED50) from 77 to 5.4 micrograms/kg while substitution at the 8-position reduced potency. Methyl substitution at various sites in the molecule was also examined. Positive inotropic activity was maintained for between 8 and 24 h after a single oral dose (100 micrograms/kg) of bemoradan in dogs, thus making it one of the most potent and long-acting orally effective inotropes yet described. Bemoradan is currently under development as a cardiotonic agent for use in the management of congestive heart failure.

Thiophene systems. 14. Synthesis and antihypertensive activity of novel 7-(cyclic amido)-6-hydroxythieno[3,2-b]pyrans and related compounds as new potassium channel activators.

The synthesis and antihypertensive activity of novel 7-(cyclic amido)-6-hydroxy-5,5-dimethylthieno[3,2-b]pyrans and related compounds are described. The compounds were tested for oral antihypertensive activity in spontaneously hypertensive rats (SHR) and selected compounds were evaluated in vitro for increases in 86Rb efflux in rabbit isolated mesenteric arteries. The effects on activity in SHR of lactam ring size, the presence of heteroatoms in the lactam ring, the relative stereochemistry at C-6 and C-7, and the substituents on the thiophene ring are examined. The best racemic compound in this series is 32, trans-5,6-dihydro-6-hydroxy-5,5-dimethyl-2-nitro-7-(2-oxopiperidin -1-yl)-5H- thieno[3,2-b]pyran, which is 10-fold more potent than cromakalim with an ED30 = 0.015 mg/kg in SHR. Compound 32 could be resolved and the antihypertensive activity determined to reside primarily in the (6S,7S)-(-)-enantiomer 41. Surprisingly, the elimination of water to give the enamides 50-52, thiophene isosteres of bimakalim, diminishes activity significantly.

Bemoradan--a novel inhibitor of the rolipram-insensitive cyclic AMP phosphodiesterase from canine heart tissue.

Canine cardiac muscle contains a type IV cyclic AMP (cAMP) phosphodiesterase (PDE) that is composed of two subtypes. One subtype is sensitive to rolipram inhibition (RSPDE), whereas the other is not inhibited significantly by rolipram (RIPDE). The RIPDE is inhibited by several cardiotonic agents operating by a PDE-inhibitory mechanism. Bemoradan [RWJ-22867; 7-(1,4,5,6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl)-2H-1,4-benzoxazin -3(4H)-one], a novel, potent positive inotropic agent, demonstrated biphasic inhibition of the fraction III enzyme from canine cardiac muscle. Inhibition by rolipram of the RSPDE converted the IC50 curves of bemoradan, indolidan, pimobendan, and imazodan to sigmoidal, monophasic curves. Lineweaver-Burk analysis yielded competitive inhibition KI values of 0.023, 0.09, 0.065 and 0.60 microM, respectively, for these compounds. The cardiotonic compounds, however, were not potent inhibitors of the Type I and Type II cAMP PDEs found in canine ventricular muscle. The order of potency for inhibiting the RIPDE cAMP PDE subtype was bemoradan greater than pimobendan greater than indolidan greater than imazodan. Bemoradan is, therefore, a potent inhibitor of the cardiac muscle cAMP PDE which could, in part, be responsible for its cardiotonic activity.

Response of rat adrenal neuropeptide Y and tyrosine hydroxylase mRNA to acute stress is enhanced by long-term voluntary exercise.

Neuropeptide Y (NPY) and catecholamines are synthesized in response to stress. Adrenal NPY mRNA and tyrosine hydroxylase (TH) mRNA were measured by Northern analysis 2 h after a single 20 min bout of shaker stress in exercised and sedentary male Sprague-Dawley rats. Long-term exercise (18 weeks of voluntary wheel running) alone did not significantly alter adrenal NPY mRNA or TH mRNA levels. However, increases in stress-induced NPY and TH mRNA abundances were significantly enhanced by long-term exercise (P < 0.01). These results suggest that long-term physical activity may enhance the ability to synthesize NPY and catecholamines under conditions of stress.

Inhibition of rabbit platelet phosphodiesterase activity and aggregation by calcium channel blockers.

Rabbit platelet cyclic AMP phosphodiesterase is inhibited by the three calcium channel blockers nifedipine, diltiazem, and verapamil with IC50's of 100 microM, 100 microM and 420 microM, respectively. Also, platelet aggregation induced by 4 microM ADP is inhibited by those compounds. Verapamil is the most potent aggregation inhibitor with an IC50 of 260 microM while diltiazem and nifedipine have IC50's of 630 microM and 840 microM, respectively. All three compounds display a maximum inhibition of 80-85%. Diltiazem and PGD2 potentiate the antiaggregatory activity of each other in that the inhibitions occurring in the presence of the combination of the two (at varying concentrations) exceed the calculated sums of the inhibitions produced by each alone. On the other hand, the antiaggregatory activities of verapamil or nifedipine, are additive with that of PGD2 in that no significant differences exist between the observed inhibitions produced by the combinations and the calculated summed values of the individual inhibitions. Our data suggest, therefore, that in addition to lowering intracellular calcium ions, which are required for platelet aggregation, the three calcium channel blockers inhibit the breakdown of cyclic AMP thereby promoting antiaggregation.

High affinity binding sites for [3H]-nitrendipine in rabbit uterine smooth muscle.

The binding properties of the high affinity binding site for [3H]-nitrendipine on rabbit uteri membranes were investigated. The specific component had a dissociation constant of 0.46 +/- .07 nM and a maximal binding of 175 +/- 11 pmol/mg. A variety of other calcium channel blockers inhibited the binding of [3H]nitrendipine with varying potencies. Flunarizine demonstrated a high potency (IC50 = 0.30 microM) in inhibiting binding while verapamil and bepridil were less potent with IC50's of approximately 0.6-1.5 microM. Diltiazem did not displace nitrendipine even at very high concentrations. Verapamil displayed negative cooperative inhibition suggesting that a second site exists on uterine membranes for the binding of other calcium channel blockers.