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PubMedDate not supplied

Seasonal patterns in eating disorder subgroups.

Patients with bulimia nervosa (BN) often have seasonal patterns of mood and appetite that compare with patterns seen in seasonal affective disorder (SAD). Seasonal patterns in other eating disorder (ED) subgroups have not been adequately described. We report on seasonal patterns in mood, weight, appetite, sleep, social activity, and energy in 154 consecutive admissions to an outpatient ED program: 60 patients with anorexia nervosa (AN), 31 with BN, 34 with a history of both AN and BN (AN/BN), and 29 with an ED not otherwise specified (ED-NOS). AN patients had significantly less seasonal variation overall than either bulimic subgroup, as measured by the global seasonality score (GSS) on the Seasonal Patterns Assessment Questionnaire (SPAQ). AN patients also showed less seasonal change in mood, weight, and energy than BN patients, and less variation in mood and appetite than AN/BN patients.

Adolescent↗
PubMed1984

Seasonal reproduction in the mongoose, Herpestes auropunctatus. IV. Organ weight and hormone changes in the female.

The mongoose, Herpestes auropunctatus, shows a well-defined breeding season in Hawaii. In this study, females were live-trapped throughout the year and sacrificed within 48 hr to obtain information about reproductive organ weights and gonadotropin levels. Pregnant females were found from February through September and lactating females from March through October. Body weight did not change significantly throughout the year, but anterior pituitary, adrenal, ovarian, and uterine weights were significantly reduced during the nonbreeding season. LH and FSH levels were extremely variable among individuals and, although mean values were higher during the breeding than during the non-breeding season, no significant differences could be demonstrated. After castration, there was not a clearcut rise in either LH or FSH, regardless of the season of the year, when animals were followed for up to l5 days. This contrasts with the male mongoose, where FSH rose significantly by 4 days after castration in either the breeding or nonbreeding season, while LH rose more slowly in the nonbreeding season but by l0 days after castration was significantly elevated and comparable to values in males castrated in the breeding season. We conclude that the female mongoose population shows less synchrony in changes in gonadotropin levels than the males, in spite of the well-defined breeding season.

Animals↗
PubMed1987

Seasonal differences in testicular receptors and steroidogenesis.

Gonadal function in most animal species exhibits considerable annual fluctuations, with gametogenesis and fertility often being confined to a short and rigidly controlled breeding season. In males, production of androgenic steroids by the testis is usually maximal immediately before and during the breeding season. In the golden hamster, seasonal regression of the testes is associated with decrease in the total content of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) receptors, and similar findings have been reported for other mammalian species. However, the concentration of LH and FSH receptors per unit of testis weight is typically elevated rather than suppressed during testicular regression. Reduction in the number of testicular LH and PRL receptors in adult golden hamsters exposed to short photoperiod is due primarily to suppression of pituitary PRL release under these circumstances. Regulation of seasonal changes in testicular FSH binding, as well as regulation of the levels of LH, PRL and FSH receptors in other seasonally breeding species remain to be elucidated. Reduction in the content of LH receptors in the testes is accompanied by reduced capacity to produce androgens in response to LH stimulation. Although these events are likely to be causally related, other mechanisms are also involved. In particular, seasonal regression is accompanied by reduced capacity of the testes to convert C21 steroid precursors into biologically active androgens. Seasonal loss of FSH receptors was reported to be accompanied by increased rather than reduced responsiveness of the Sertoli cells to FSH, thus resembling the situation in immature animals. It can be concluded that alterations in the ability of the testes to bind pituitary gonadotropins and to respond to gonadotropic stimulation are among the mechanisms responsible for seasonal shifts between gonadal activity and quiescence.

Animals↗
PubMed1996

Seasonality in squirrel monkeys (Saimiri sciureus): social facilitation by females.

The extent to which social living arrangements influenced seasonal changes in physiology and behavior was examined in adult squirrel monkeys (Saimiri sciureus). Data were collected over 20 months (encompassing two breeding seasons) from animals that were housed in three mixed-sex social configurations that varied in the number of heterosexual and isosexual social partners. For both sexes, the presence of multiple females was found to facilitate reproduction. Females housed with other females were more likely to exhibit seasonal ovarian cyclicity and tended to have higher conception rates. Social facilitation of reproduction was particularly prominent for subordinate females. The presence of same-sex companions also resulted in reduced adrenocortical output in females during the first nonbreeding season. In males, the availability of multiple females increased plasma testosterone levels, except in the presence of more dominant males. Seasonal increases in male weight coincided with increased cortisol levels and were most prominent in social groups containing multiple females. The influence of multiple females on male seasonality occurred despite the finding that male-female interactions were infrequent and, in fact, occurred less frequently when isosexual partners were available. Unexpectedly, affiliative social interactions between same-sex and opposite-sex partners occurred less frequently during the breeding season. As expected, behaviors associated with sex tended to increase during the breeding season. Very little agonism was observed during the course of the study and there was no evidence of interanimal competition for mates.

Animals↗
PubMed1991

Ontogenetic and seasonal changes in immunoreactive vasotocin in the canary brain.

Using immunocytochemistry the central VT system of the canary was examined during ontogeny and throughout the season. At 4 weeks of age no VT-immunoreactive staining in the bed nucleus of the stria terminalis and lateral septum was present, but VT-containing cells and fibers were clearly visible in the nucleus paraventricularis of the hypothalamus. At 13 weeks of age a weak VT immunoreactivity appeared in the bed nucleus of the stria terminalis and lateral septum. This VT immunostaining increased progressively till at the age of 28 weeks adult levels were reached. In adulthood, cells and fibers in the lateral septum and the bed nucleus of the stria terminalis contained the highest amounts of immunoreactive VT during the breeding season, whereas during the molt, in august, a decreased VT immunostaining was noted. These seasonal changes in VT immunostaining coincided with variations in circulating testosterone level, which is high during the breeding season and low during the molt. In the ventral capsular region surrounding the nucleus robustus archistriatalis a clear VT-immunoreactive fiber pattern was demonstrated at the age of 8 and 13 weeks in both female and male canaries. Although the size of this nucleus varies during the season no seasonal changes in the VT-immunoreactive pattern surrounding the RA were detected. The data suggest that the activity of the VT system slowly increases during development. At adulthood seasonal and gonadal hormone-dependent changes occur in the limbic VT system only. The VT immunostaining associated with the nucleus robustus archistriatalis however, is resistant to seasonal and gonadal influences.

Aging↗
PubMed1994

Effect of light and season on pain and depression in subjects with rheumatic disorders.

The clinical and neurochemical association between depression and season noted in seasonal affective disorder (SAD) has suggested that clinical pain might also be linked to season, perhaps through similar neurochemistry or the known association of depression with pain. We investigated the pain-light season/dark season hypothesis in 2523 rheumatic disease outpatients by examining VAS Pain and VAS Global Severity scores, as well as levels of depression and functional disability. No clinically significant difference in pain severity between season (or individual month) was noted for the consecutive outpatients at their first clinic visit, nor in sub-analyses using paired light and dark season visits. A slight trend toward increased pain severity in lighter months by about 3% compared to darker months was identified. No effect of season was seen on depression scores. In a subset of patients with high depression scores, rheumatoid arthritis and osteoarthritis patients, respectively, reported 16% and 7% greater pain scores in light compared to dark months, but fibromyalgia patients had stable scores. Season does not appear to play an important role in pain and/or depression in rheumatic disorders.

Aged↗
PubMed1996

The role of technical, biological and pharmacological factors in the laboratory evaluation of anticonvulsant drugs. VI. Seasonal influences on maximal electroshock and pentylenetetrazol seizure thresholds.

There is strong evidence for circadian rhythmicity in certain seizure types, whereas only a few studies have addressed the possibility of seasonal rhythms in convulsive activity. In the present experiments, seizure thresholds to different types of seizures were determined twice per month over a period of 13 months in mice under controlled environmental conditions, i.e., constant photoperiod, temperature, humidity, and food. Each group of animals was used for only one experiment, and the age of the mice used per month was the same throughout the study. Furthermore, all experiments were done at the same time in the morning to avoid circadian variation. Thresholds for the following seizure types were determined: (1) tonic hindlimb seizures induced by electrical (transauricular) stimulation; (2) myoclonic seizures induced by intravenous (i.v.) infusion of pentylenetetrazol (PTZ); (3) generalized clonic seizures in response to i.v. PTZ; and (4) tonic forelimb seizures induced by PTZ. A significant seasonality was determined for myoclonic and clonic PTZ seizure thresholds with highest thresholds between February and April and lowest thresholds between July and September. No clear seasonality was seen for chemically or electrically induced tonic seizures. Determination of plasma corticosterone did not disclose any seasonal rhythm in adrenal corticosteroid production that resembled the circannual variation in myoclonic and clonic seizure thresholds. In conclusion, our experiments suggest the existence of seasonal rhythms in PTZ seizure thresholds in laboratory animals despite standardized environmental conditions. A possible explanation for the findings may be the known seasonal alteration of the geomagnetic field which, by its effect on the pineal production of melatonin, may act as a seasonal synchronizor ("zeitgeber") in animals in the absence of other synchronizing forces, such as seasonal changes in photoperiod and ambient temperature.

Animals↗
PubMed2005

Circadian variations in plasma concentrations of melatonin and prolactin during breeding and non-breeding seasons in yak (Poephagus grunniens L.).

Circadian variations of plasma melatonin and prolactin concentrations were determined during breeding as well as non-breeding seasons in yak. Blood samples (5 ml) were collected during different phases of estrous cycle, viz. early (0-6 days), mid (7-12 days) and late luteal (13-19 days) at 2 h interval for 24 h from eight yaks during one breeding month (November); the same yaks were bled at 2 h interval during one non-breeding month (February) for 24 h. Plasma melatonin concentrations rose sharply (P < 0.01) after sunset to record peak concentrations between midnight and 2 a.m. declining sharply thereafter in both breeding as well as non-breeding seasons. Basal melatonin concentrations were recorded between 0600 and 1600 h. Stage of luteal phase did not influence the diurnal hormone change (P < 0.01). In the breeding season, mean plasma prolactin concentrations displayed circadian variations with maximum value at 0400 h (41.22+ /- 1.5 ng/ml) and minimum at 1400 h (12.0 +/- 4.02 ng/ml). In the non-breeding season plasma prolactin concentrations showed circadian variation with maximum value at 0000 h (59.9 +/- 10.5 ng/ml) and minimum at 1200 h (32.13 +/- 3.2 ng/ml). A positive correlation in breeding (r = 0.75) and in non-breeding season (r = 0.65) between circadian changes in mean plasma prolactin and melatonin concentrations were seen. Circadian changes of mean plasma melatonin concentrations during breeding and non-breeding seasons were not different (P > 0.05). However, mean plasma prolactin concentrations were found to be higher (P < 0.01) in the non-breeding season. Three conclusions were drawn from the study: (i) melatonin and prolactin concentrations followed a circadian pattern of secretion (ii) melatonin and prolactin secretion may be closely interrelated and (iii) higher prolactin concentrations during the non-breeding season could be due to nutritional and environmental stress and hence might be contributing to lack of cyclicity.

Animals↗
PubMed2006

Down regulation of bisphenol A glucuronidation in carp during the winter pre-breeding season.

Environmental pollution by bisphenol A is prevalent in many rivers. The influence of bisphenol A on the reproductive organs of carp has been demonstrated to be serious, especially in the winter pre-breeding season. Although bisphenol A is detoxified as bisphenol A-glucuronide in carp organs, principally the intestine, the seasonal variation in the efficiency of the detoxification is not known. To estimate the seasonal risk of bisphenol A in carp, we investigated seasonal changes in microsomal UDP-glucuronosyltransferase activity toward bisphenol A in male-carp. Seasonal elimination efficiency of bisphenol A was also examined by organ perfusion in everted intestine. No marked seasonal differences were observed in UDP-glucuronosyltransferase activity toward 1-naphthol, but high activity toward sex steroid hormones (testosterone and estradiol) was observed in the winter pre-breeding season. Low UDP-glucuronosyltransferase activity toward bisphenol A was indicated in winter. The addition of bisphenol A into the mucosal fluid of the everted intestine resulted in excretion of bisphenol A into the mucosal side of the intestine as the metabolite, bisphenol A-glucuronide. Excretion of bisphenol A-glucuronide from carp intestine was highest in summer (proximal intestine: 13.3 nmol; middle intestine: 8.3 nmol; distal intestine: 7.9 nmol) and lowest in winter (proximal intestine: 1.0 nmol; middle intestine: 1.0 nmol; distal intestine: 0.9 nmol). These results suggest that metabolism and excretion of bisphenol A in carp hepatopancreas and intestine are impaired by down regulation of UDP-glucuronosyltransferase activity in the winter pre-breeding season.

Animals↗
PubMedDate not supplied

Seasonal differences in psychopathology of male suicide completers.

Suicide is known to vary according to season, with peaks in the spring and troughs in the winter. The presence of psychopathology is a significant predictor of suicidality, and it is possible that the seasonal variation of suicide completion may be related to seasonality in the manifestation of psychiatric disorders common to suicide completers. In the current study, we evaluated 115 French-Canadian male suicide completers from the Greater Montreal Area for DSM-IV psychiatric disorders using proxy-based diagnostic interviews. Subjects were assessed for seasonal differences in the prevalence of DSM-IV psychiatric diagnoses just before their deaths. Diagnoses of major depressive disorder (MDD) without comorbid cluster B personality disorders, and schizophrenia were differently distributed between seasons. Most (63.4%) subjects with MDD committed suicide in the spring/summer (P =.038). However, closer examination revealed that depressed suicides with comorbid cluster B personality disorders did not show seasonality, while 83.3% of depressed suicides without comorbid cluster B personality disorders committed suicide in the spring/summer (P =.019). 87.5% of those suicides with schizophrenia committed suicide in the fall/winter (P =.026), and the only suicide with schizophrenia who died in the spring/summer was also the only one without positive symptomology. Our study is limited to male suicide completers, and results should not be generalized to women. We conclude that seasonal variation in suicide manifests itself differently in patients with different psychopathology. These findings indicate that assessment of suicide risk may need to include consideration of possible seasonal effects, depending on psychopathology.

Adult↗
PubMed2006

Seasonal variation in paroxysmal atrial fibrillation documented by 24-hour Holter electrocardiogram.

BACKGROUND: The incidence of various cardiovascular diseases is known to exhibit seasonal variations, but seasonal patterns of paroxysmal atrial fibrillation (AF) have not been well characterized. OBJECTIVE: The objective of this study was to determine whether seasonal variation affects the incidence of paroxysmal AF and whether this pattern is affected by patient age. METHODS: We identified 258 paroxysmal AF episodes in 237 patients (age 65 +/- 14 years, mean +/- standard deviation; age range 16-95 years) among 12,390 consecutive 24-hour Holter electrocardiogram recordings obtained from 2001 to 2005 at our institute. Seasonal variations were analyzed by both month and by season. The relative risk (RR) of AF for each period was determined as being high or low in relation to the overall mean incidence. The association among clinical covariates and risk of paroxysmal AF was tested by logistic regression analysis. RESULTS: The incidence of paroxysmal AF was highest in September (RR = 1.40, 95% confidence interval [CI] 1.36-1.44) and lowest in June (RR = 0.52, 95% CI 0.50-0.54), with an RR difference of 63% (P < .001) among all patients. Patients aged > or =65 years demonstrated a peak incidence in September (RR = 1.46, 95% CI 1.41-1.51) and a minimum in June (RR = 0.55, 95% CI 0.52-0.58), while those aged <65 years showed a peak incidence in December (RR = 1.33, 95% CI 1.27-1.39) and a minimum in June (RR = 0.49, 95% CI 0.45-0.53). The incidence of paroxysmal AF also showed an autumn peak (RR = 1.21, 95% CI 1.16-1.27) and a summer minimum (RR = 0.66, 95% CI 0.62-0.70), with an RR difference of 53% (P < .001) among all patients. This seasonal variation in paroxysmal AF did not differ between patients of different age ranges. Clinical covariates including underlying disease or medications did not influence the monthly or seasonal variation in paroxysmal AF. There was a significant inverse relationship between the incidence of paroxysmal AF and the length of daylight in patients aged <65 years (r = -0.57, P < .05). CONCLUSION: There was a significant seasonal variation in paroxysmal AF, with maximum and minimum incidences in autumn and summer, respectively, and this pattern was not age dependent.

Adolescent↗
PubMed2004

Secular trends and seasonality in first-time hospitalization for acute myocardial infarction--a Danish population-based study.

BACKGROUND: The incidence of acute myocardial infarction has declined in several Western countries during the last decades. The incidence and mortality of acute myocardial infarction follow a seasonal pattern. We examined if changes in the incidence of acute myocardial infarction were associated with any changes in seasonality. METHODS: The study was based on 17,989 patients hospitalized with first-time acute myocardial infarction identified in the Hospital Discharge Registry of the County of North Jutland, Denmark, from 1 January 1983 to 31 December 1999. The seasonality of acute myocardial infarction was estimated using a Poisson regression model. RESULTS: The incidence rate decreased by 3.2% (95% confidence interval: 2.7-3.3%) annually. Hospitalizations followed different seasonal patterns depending on age, but not on gender. In the <59-year-old group, the seasonal pattern was dominated by a broad spring peak (April/May) and a minor autumn peak. With increasing age, the spring peak decreased while the autumn peak increased and moved towards December. A seasonal pattern dominated by one peak (December) and one trough (August) was found in the > or =80-year-old category. The shape and extent of these seasonal patterns remained stable throughout the study period despite the decline in hospitalizations for acute myocardial infarction. CONCLUSION: Hospitalizations for first-time acute myocardial infarction decreased from 1983 to 1999, but the seasonal pattern remained stable over time.

Denmark↗
PubMed2004

Differences in Cd and Zn bioaccumulation for the flood-tolerant Salix cinerea rooting in seasonally flooded contaminated sediments.

Several authors suggest that a hydrological regime aiming at wetland creation is a potential management option that favours reducing bioavailability for metal-contaminated sites. The hydrological conditions on a site constitute one of the many factors that may affect the availability of potentially toxic trace metals for uptake by plants. Bioavailability of Cd, Mn and Zn on a contaminated dredged sediment landfill (DSL) with variable duration of submersion was evaluated by measuring metal concentrations in the wetland plant species Salix cinerea in field conditions. Longer submersion periods in the field caused lower Cd and Zn concentrations in the leaves in the first weeks of the growing season. Foliar Cd and Zn concentrations at the end of the growing season were highest on the initially flooded plot that emerged early in the growing season. Foliar Zn concentrations were also high at a sandy-textured oxic plot with low soil metal concentrations. Zn uptake in the leaves was markedly slower than Cd uptake for trees growing on soils with prolonged waterlogging during the growing season, pointing at a different availability. Zn availability was lowest when soil was submerged, but metal transfer from stems and twigs to leaves may mask the lower availability of Cd in submerged soils. Especially for Cd, a transfer effect from one growing season to the next season was observed: oxic conditions at the end of the previous growing season seem to determine at least partly the foliar concentrations for S. cinerea through this metal transfer mechanism. Duration of the submersion period is a key factor for bioavailability inasmuch as initially submerged soils emerging only in the second half of the growing season resulted in elevated Cd and Zn foliar concentrations at that time.

Disasters↗
PubMed2004

Seasonal variation in plasma sex steroid concentrations in juvenile American alligators.

Seasonal variation in plasma sex steroid concentrations is common in mature vertebrates, and is occasionally seen in juvenile animals. In this study, we examine the seasonal pattern of sex hormone concentration in juvenile American alligators (Alligator mississippiensis) and make a limited comparison of these seasonal patterns on two different lakes in Florida. Male juvenile alligators from a reference lake, Lake Woodruff, displayed temporal patterns in plasma testosterone (T) concentrations that appear to be seasonal. A similar pattern in plasma estradiol-17beta (E(2)) was observed in juvenile females from Lake Woodruff. Males had significantly elevated T concentrations during the spring and late summer, whereas females had elevated E(2) in the spring and late summer and significantly depressed E(2) concentrations during the winter. A limited 4-month survey of animals from contaminated Lake Apopka found a lack of such seasonality. These results suggest that: (1) healthy wild populations of juvenile alligators have a prolonged peripubescent period that is marked by seasonal hormonal cycles, (2) juvenile alligators exposed to environmental contaminants can lack such seasonal cyclicity, and (3) future studies of juvenile alligators should incorporate such seasonality into the experimental design.

Alligators and Crocodiles↗
PubMed2004

Seasonal changes in adrenocortical responses to acute stress in polygynous male bush warblers (Cettia diphone).

The adrenocortical response to acute stress as measured by increase in plasma levels of corticosterone following capture, handling, and restraint over an hour was estimated in free-living male bush warblers at different times of the breeding season on their breeding ground in Chichibu, Honshu, Japan. Initial plasma levels of corticosterone showed a seasonal change, being moderate in April, highest in May to July and declined in late August. In contrast, the stress response was suppressed at the early stage of the breeding season, April and May, and just after the breeding season, late August. In June, July, and early August, the response was obvious although the initial levels of corticosterone were high. These results are different from those of monogamous passerine birds so far studied in which adrenocortical response is obvious at the early stage of breeding season and the response is suppressed later stage when the male is involved in parental care. The results suggest that during a course of the breeding season, male bush warblers that take a polygynous breeding strategy may decrease the amplitude of the adrenocortical response to acute stress at the early stage of the breeding season so as to allow establishment and defense of a territory. The birds became more sensitive to acute stress later the breeding season when they already had females incubating, feeding hatchlings or even fledgling. This change of stress response is likely to be a reflection of polygynous breeding strategy of the species.

Acute Disease↗
PubMed2006

Seasonal changes in hypothalamic-pituitary-adrenal axis sensitivity in free-living house sparrows (Passer domesticus).

Recent evidence indicates that house sparrows (Passer domesticus) seasonally regulate corticosterone responses to capture, handling, and restraint. Responses during molt and in the fall are lower than responses in the winter and while breeding. This study tested whether changes in either adrenal tissue responsiveness to adrenocorticotropin (ACTH) or pituitary responsiveness to corticotropin releasing factor (CRF) or arginine vasotocin (AVT) could provide the mechanism regulating these seasonal changes. House sparrows were captured at two sites (Massachusetts and New Mexico, USA) and during the above four seasons and injected with exogenous ACTH, CRF, and AVT. ACTH stimulated further corticosterone release in all birds except Massachusetts birds in the winter, suggesting that reduced adrenal sensitivity to ACTH cannot explain reduced corticosterone release during fall and molt. However, exogenous ACTH was less effective during molt at both sites, implying that adrenal sensitivity does change. Pituitary sensitivity also changed seasonally, but these pituitary changes did not match the seasonal changes in corticosterone release. CRF and AVT only succeeded in elevating corticosterone in the spring in Massachusetts birds and in the winter in New Mexico birds, whereas CRF alone also stimulated corticosterone release in New Mexico birds in the fall. Taken together, these data indicate that house sparrows can alter the amount of corticosterone released from adrenal tissue, the amount of ACTH released from the pituitary, and the amount of CRF and AVT released from the hypothalamus, but that none of these changes correlate with seasonal changes in corticosterone release. Consequently, seasonal modulation of corticosterone release in house sparrows appear to result from a complicated mix of adrenal, pituitary, and hypothalamic changes that also vary seasonally.

Adrenocorticotropic Hormone↗
PubMed2006

Testosterone and its effects on courtship in golden-collared manakins (Manacus vitellinus): seasonal, sex, and age differences.

Male golden-collared manakins gather on leks and perform an acrobatic display to attract females. In temperate breeding species, testosterone (T) activation of courtship displays has been well studied. Few studies have examined T activation of displays in tropical species; even fewer have explored the activational role of T in elaborate courtship displays such as in the manakin. In some tropical species, including manakins, territorial aggression or song behavior are uncoupled from T. We have previously shown that T activates display behavior in manakin males when endogenous T levels are low in the non-courtship season. To understand how T functions in breeding birds, we examined T levels in a large group of manakins sampled during the courtship and non-courtship season. In addition, during the courtship season, we gave T implants to adult males, juvenile males, and females. We found that T levels were low during the non-courtship season and comparatively higher on average during the courtship season. However, T levels were low in many adult males during the courtship season, especially when compared to temperate breeding species. Regardless of initial endogenous T levels during the courtship season, T implants did not increase the display frequency of adult males. T-treated females and juvenile males did display under similar conditions. Our data suggest that the effects of T on manakin display vary with season, sex, and age and that high T is not necessary for display.

Aging↗
PubMed2003

Seasonal alterations in adrenocortical cell function associated with stress-responsiveness and sex in the eastern fence lizard (Sceloporus undulatus).

We characterized steroidogenic properties of dispersed adrenocortical cells from field-active male and female eastern fence lizards (Sceloporus undulatus) to investigate whether alterations in cell function could, in part, explain seasonal variation in baseline and stress-induced plasma corticosterone (B). Lizards were collected during the breeding and postbreeding seasons and shortly prior to hibernation. Dispersed cells in vitro produced B, aldosterone (ALDO), and progesterone in response to 8-Br-cAMP, 25-(OH)cholesterol, adrenocorticotropin (ACTH; as little as 100 fM), and angiotensin II. Maximal progesterone, B, and ALDO responses to ACTH were roughly 1000%, 500%, and 100% greater than corresponding basal values. Angiotensin II was an effective steroidogenic stimulant but much less so than ACTH. Corticosteroid production exhibited considerable steroid-specific variation among seasons. Maximal ACTH-induced B production was lower in the postbreeding season than at either of the other two measurement points, essentially opposite to the pattern for ALDO. Males and females generally produced B at similar rates, but ALDO and progesterone showed numerous sex differences that usually covaried between the two steroids. Cellular sensitivity to 25-(OH)cholesterol and angiotensin II showed few sex differences or seasonal changes. In contrast, sensitivity to ACTH decreased markedly from the breeding to the postbreeding season in males, corresponding to the decrease in stress-responsiveness, and in both sexes was considerably lower prior to hibernation than during the breeding season. Under some conditions, plasma B may be limited by the production capacity of adrenocortical cells. In summary, seasonal variations in body condition, reproductive activity, and baseline and stress-induced plasma B may be attributed at least in part to alterations in adrenocortical cell steroidogenic function.

8-Bromo Cyclic Adenosine Monophosphate↗