Abstract:
:The aim of the present study was to determine the relationship between seasonal variation in levels of insulin, cortisol, and corticosterone and body mass in a natural population of golden-mantled ground squirrels (Spermophilus saturatus) over the active season, from April to August. The body mass of females is at an active season minimum on emergence from hibernation, increases during pregnancy and lactation, and shows a further rise during fattening, reaching a peak in August. Males are heavier than females on emergence from hibernation, lose mass during the mating period, then gradually increase to a maximum in August. Plasma insulin titers generally reflected these patterns of change in body mass. Levels in males were almost double those of females on emergence, then decreased as body mass was lost during mating. Male values increased in July and peaked in August, coincident with the body mass maximum. Females, in contrast, showed very low insulin levels in April on emergence and increased levels during lactation, continuing high into the fattening period. Corticosterone levels were low in both sexes at the beginning of the season and rose throughout most of the active season; female levels exceeded those of males during the lactation phase. Cortisol titers gradually decreased over the first half of the active season in both sexes, but later increased to a seasonal maximum at the end of the season, coincident with the peak in body mass.(ABSTRACT TRUNCATED AT 250 WORDS)
journal_name
Gen Comp Endocrinoljournal_title
General and comparative endocrinologyauthors
Boswell T,Woods SC,Kenagy GJdoi
10.1006/gcen.1994.1189subject
Has Abstractpub_date
1994-12-01 00:00:00pages
339-46issue
3eissn
0016-6480issn
1095-6840pii
S0016-6480(84)71189-0journal_volume
96pub_type
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