The Effects of Gender and Ovarian Steroids on Insular Function and Glucose Homeostasis in The Prepuberal Gonadectomized Male and Female Dog
Blank-Bottorff, Ruth Ellen
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https://hdl.handle.net/2142/71327
Description
Title
The Effects of Gender and Ovarian Steroids on Insular Function and Glucose Homeostasis in The Prepuberal Gonadectomized Male and Female Dog
Author(s)
Blank-Bottorff, Ruth Ellen
Issue Date
1985
Department of Study
Veterinary Medical Science
Discipline
Veterinary Medical Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Veterinary Science
Abstract
The effects of sex, estrogen, and progesterone on glucose and insulin parameters were studied. Sixteen male and 16 female dogs were gonadectomized before 6 months of age. Silastic implants containing estrogen were placed subcutaneously in 8 dogs of both sexes to approximate proestrous estrogen levels. An intravenous glucose tolerance test was performed after 14 days of estrogen exposure.
Fasting plasma glucose levels were higher in female than male dogs (p = .05); glucose disappearance rates did not differ between the sexes. Fasting serum insulin levels were not different between sexes, but insulin peak responses and insulinogenic indices 5 minutes after glucose injection were larger in male than female dogs (p = .02). Estrogen did not affect fasting glucose and insulin levels, insulin peak responses, and insulinogenic indices, but glucose disappearance rates were lower in estrogen-treated dogs than nonestrogen-treated dogs (p = .02).
Estrogen treatment in Experiment II followed the pattern of Experiment I. After 2 weeks, estrogen was withdrawn and implants containing progesterone were placed in 4 of the estrogen- and nonestrogen-treated dogs of both sexes to approximate diestrous progesterone levels. Glucose tolerance tests were performed after 3, 6, and 9 weeks of progesterone exposure.
When averaged over all tolerance tests, male dogs had larger insulin peak responses (p = .02) and insulinogenic indices (p = .01) 5 minutes after glucose injection, previous estrogen treatment caused lower insulin levels during the second half hour following glucose administration, and progesterone did not affect insulin and glucose parameters. In the first tolerance test, dogs with progesterone had less insulin in peripheral blood from 30 to 60 minutes than dogs without progesterone (p = .03), dogs with progesterone had more glucose in peripheral blood from 15 to 60 minutes than dogs with neither or both estrogen and progesterone (p = .01), and dogs with estrogen had more glucose in peripheral blood from 5 through 60 minutes than dogs with neither or both estrogen and progesterone (p = .01).
These studies suggest that an inherent sexual difference in glucose-stimulated insulin secretion exists in dogs, estrogen and progesterone decrease peripheral insulin levels, and estrogen and progesterone elevate glucose levels in a pattern consistent with insulin resistance.
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