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J. Charles Eldridge, PhD

J. Charles Eldridge, PhD - Research


Our lab is no longer active.  Over a period spanning four decades our basic research theme was the study of mammalian hormones and endocrine systems, principally those involved with reproduction.  We investigated aspects of hormone action and secretion in a variety of problem areas, including growth and development, aging, substance abuse, stress, and toxicology.  The rapidly expanding field of endocrine toxicology was our most recent focal interest.  

Neuroendocrine Control of Gonadotropin Secretion   

The laboratory of V.B. Mahesh at the Medical College of Georgia was just beginning an interest in pituitary gonadotropic hormones when I arrived as a graduate student.  The invention of RIA technology permitted, for the first time, measures of gonadotropin secretion in blood.  We were among the first labs in the country to establish assays for FSH, LH and prolactin in rats, which afforded a unique opportunity to probe fundamental questions concerning feedback mechanisms controlling secretion of these hormones.    

My initial interest was the immature, prepubertal state, to ask whether well-known feedback loops between gonads and hypothalamic-pituitary axis of adults was operational before puberty.  The unanswered question was whether puberty was accomplished by “adjusting the sensitivity” of a functional feedback loop, or whether it occurred by activation of a previously quiescent system (“flipping a switch”).  Our results suggested the former is true.  

Link to publications and presentations  

Stress and Aging  

At Wake Forest, the Department of Physiology and Pharmacology developed a collaborative program to investigate mechanisms of neural aging.  Our lab focused on the potential roles of endocrine stress as a promoter.  Using rodents, we were involved in the development of chronic stress models that permitted investigation of effects at different ages, as well as effects on the development of senescence.    

A particularly active area, conducted in collaboration with Dr. Philip Landfield, identified possible participation by glucocorticoid secretion responding to stress in the progression of senescent alterations in cells of the hippocampus.  A major finding was that the flexibility, or plasticity, of resilient glucocorticoid-responsive systems in the brain appear to be compromised with advancing age and exposure to stressful environments.  Our studies participated in significant adjustments to hypotheses of brain aging.   

Link to publications and presentations

Substance Abuse  

The arrival of Dr. James Smith as department chair ushered in an exciting era of basic research on neural mechanisms of substance abuse.  Supported by major funding from both NIDA and NIAAA, a large collaborative effort led to one of the nation’s preeminent programs for training and research on stimulants, opiates, and alcohol.     

Our lab pursued the possible participation of endocrine systems in two areas.  One was to investigate interactions of stress and cannabinoids in rodents, asking specifically how THC and related substances might exert influence on brain targets for glucocorticoids.  A second research theme studied the potential involvement of sex hormones of adult cycling female rats in the acquisition and maintenance of ethanol dependency.  

Link to publications and presentations  

Endocrine Interactions of Pesticides  

In the late 1980’s our lab began an interest in endocrine toxicology, the mechanisms by which environmental pollutants, now often called “endocrine disruptors”, can interact with synthesis and actions of hormones.  Our activity drew on our background in endocrine physiology and pharmacology, and more specifically the hormonal control of reproduction.  This led to a substantial program of study on chlorotriazine herbicides.    

Chlorotriazines, principally atrazine, are a class of herbicides used widely in the agriculture industry.  Following earlier reports of the premature appearance of mammary tumors in female rats during long-term atrazine exposure, we determined that the herbicides are not estrogenic (a property that would directly stimulate tumor growth).  We then noted irregularities of estrous cycling patterns in treated female rats and found that atrazine administration diminished pituitary LH surges necessary for regular, cyclic ovulation.  This failure of rats to ovulate could lead to an elevated estrogen environment and promotion of mammary tumor growth.  On a broader scale our findings served to highlight the importance of monitoring estrous cycling patterns and measures of reproductive hormones in the conduct of chronic toxicology protocols for regulatory review.   

Future link to publications and presentations

Xenoestrogen Receptor Binding  

It is suspected that many hormonally active chemicals contaminate the environment.  One group of particular concern are substances that can imitate or inhibit estrogen action.  Estrogens principally act on cells via specific receptor proteins, so one way to identify putative estrogen agonists or antagonists is to assess their ability to bind to estrogen receptors in vitro.  With support from the US Environmental Protection Agency, our lab investigated binding properties of a number of putative chemicals selected on the basis of structure.  

Future link to publications and presentations  

Other Research  

In addition to the focal areas described above, we were fortunate to be invited to participate in an interesting variety number of other research projects.  Some were brief activities that we were not able to continue, such as my very first meeting presentation and journal publication, from my master’s thesis work at Northern Illinois, to some protocol development for the clinical diagnostic laboratories at the Medical University of South Carolina, to some productive collaborative work with friends and colleagues.    

In particular, our ability to measure various hormones led to invitations to join a number of interesting studies of infertility, adrenocortical physiology, hypertension pharmacology, metabolic neuroendocrinology, the blood-brain barrier and even a student’s doctoral dissertation research in virology at another university.  The collaborations were productive as well as interesting.  

Future link to publications and presentations


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