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Coping with pregnancy after 9months in the dark: Post-hibernation buffering of high maternal stress in arctic ground squirrels.

Abstract：

:Pregnancy and lactation are key times in the life of female mammals when energetic resources must be brought to bear to produce and nurture offspring. Changes in glucocorticoid (GC) levels are central to this objective, due to their roles in modulating development and physiology and in mediating energetic tradeoffs. We examined GC changes over reproduction in a species living in a harsh seasonal environment: the arctic ground squirrel (Urocitellus parryii). Females become pregnant immediately after emerging from a ∼9month hibernation, and then must begin this pregnancy during an additional month of freezing temperatures and limited food availability. We measured plasma levels of total cortisol, corticosteroid-binding globulin (CBG), and free cortisol in unstressed females at three stages: not-visibly pregnant, visibly pregnant, and lactating. Total cortisol levels were similar in all stages, but CBG levels increased 4-fold from the not-visibly pregnant stage to visibly pregnant and lactating stage. As a result, the free cortisol fraction declined from 51% of total cortisol when females were not-visibly pregnant to only 5% when they were visibly pregnant (remaining low and stable throughout pregnancy) and 10% when they were lactating. This pattern is markedly different from that seen in other mammals, where 10% or less of GCs are free and these tend to increase during gestation. We postulate that the high free cortisol just prior to visible pregnancy is a seasonal adaptation relating either to the pronounced physiological changes the female must undergo after emerging from hibernation and immediately getting pregnant, or to the mobilization of body reserves for energy to permit pregnancy, or both. Thereafter, high CBG levels may shield the developing offspring from the negative effects of cortisol overexposure.

journal_name

Gen Comp Endocrinol

journal_title

General and comparative endocrinology

authors

Edwards PD,Boonstra R

doi

10.1016/j.ygcen.2015.11.004

subject

Has Abstract

pub_date

2016-06-01 00:00:00

pages

1-6

eissn

0016-6480

issn

1095-6840

pii

S0016-6480(15)30021-6

journal_volume

232

pub_type

杂志文章

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Coping with pregnancy after 9months in the dark: Post-hibernation buffering of high maternal stress in arctic ground squirrels.