| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Department of Ecology and Evolutionary Biology, UC Santa Cruz, Santa Cruz, California, United States; Department of Biology, Sonoma State University, Rohnert Park, California, United States
2 Department of Biology, Sonoma State University, Rohnert Park, California, United States
* To whom correspondence should be addressed. E-mail: champagn{at}biology.ucsc.edu.
Fasting is associated with a series of physiological responses that protect body tissues from degradation by efficiently using expendable energy reserves while sparing protein. Lactation requires the mobilization of maternal nutrients for milk synthesis. The rare life-history trait of fasting simultaneous with lactation results in the conflicting demands of provisioning offspring while meeting maternal metabolic costs and preserving maternal tissues for her own survival and future reproduction. Certain tissues continue to require glucose for operation during fasting and might constrain tissue mobilization for lactogenesis due to a need for gluconeogenic substrates. This study investigated glucose flux, glucose cycle activity, and the influence of regulatory hormones in fasting lactating northern elephant seals. Measurements were taken early (5 days) and late (21 days) during the lactation period and, as a non-lactating comparison, after the completion of molting. Glucose cycle activity was highly variable in all study groups and did not change over lactation (p > 0.3); whereas endogenous glucose production decreased during lactation (t = -3.41, p = 0.008). Insulin and insulin to glucagon molar ratio decreased across lactation (t = 6.48, 4.28; p = 0.0001, 0.002) while plasma cortisol level increased (t = 4.15, p = 0.002). There were no relationships between glucose production and hormone levels. The glucose production values measured exceeded that predicted from available gluconeogenic substrate indicating substantial glucose recycling in this species.
This article has been cited by other articles:
|
|
 |
|
  D. Verrier, R. Groscolas, C. Guinet, and J. P. Y. Arnould Physiological response to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups: metabolic rates, energy reserve utilization, and water fluxes Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2009; 297(5): R1582 - R1592. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. A. Fowler, C. D. Champagne, D. S. Houser, and D. E. Crocker Hormonal regulation of glucose clearance in lactating northern elephant seals (Mirounga angustirostris) J. Exp. Biol., September 15, 2008; 211(18): 2943 - 2949. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. S. Houser, C. D. Champagne, and D. E. Crocker Lipolysis and glycerol gluconeogenesis in simultaneously fasting and lactating northern elephant seals Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2007; 293(6): R2376 - R2381. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| Visit Other APS Journals Online |
