Donald R. Koritnik, Ph.D.
Associate Professor of Pharmacology

Background:

Dr. Koritnik received his B.S. and M.S. in zoology / physiology and a Ph.D. degree from the University of Wyoming. His postdoctoral training was in the Reproductive Endocrinology Program at the University of California Medical School in San Francisco. Prior to joining the faculty at IUSM-Ft. Wayne, Dr. Koritnik was on the faculty in Comparative Medicine at the Bowman Gray Medical School of Wake Forest University.

Teaching Responsibilities:

Dr. Koritnik is currently Course Director for Medical Pharmacology and lectures on reproductive physiology and endocrinology in Medical Physiology.

Past Research Interests:

Thesis studies involved the endocrine control of metabolism in the ovine fetus during late gestation. Postdoctoral research characterized the regulation of the fetal zone of the non-human primate adrenal during the perinatal period and characterized some of the developmental changes in the pituitary-gonadal and pituitary - adrenal axes of non-human primates prior to puberty. Subsequent studies investigated gender differences in metabolism associated with obesity and atherosclerosis. Some of these studies characterized estrogen and androgen receptors in the liver of cynomolgus monkeys and documented gender differences and changes associated with contraceptive steroid treatments. Dr. Koritnik has more than 60 publications dealing with various aspects of reproduction, endocrinology and metabolism.

Current Research Summary:

Current efforts are focused on the effects of reproductive steroid hormones and their synthetic analogs on nitric oxide synthase. This enzyme, in releasing nitric oxide from arginine substrate, plays a major role in intercellular signaling. In coronary and uterine arteries, nitric oxide release by the endothelium increases cyclic GMP which results in relaxation of smooth muscle. In the brain, nitric oxide is a neurotransmitter which can release various hypothalamic releasing factors including gonadotropin releasing hormone. In the uterus and fallopian tubes, nitric oxide relaxes smooth muscle. Recently, evidence has emerged that nitric oxide inhibits steroidogenesis in ovarian follicles. Our research has produced evidence that estrogens increase nitric oxide in arteries and uterine tissues and that progesterone may have an opposite effect. My research utilizes molecular techniques to investigate the mechanisms associated with changes in nitric oxide synthase activity in different tissues. In most systems, estrogen-mediated events require estrogen receptor action through genomic mechanism. Our inability to find estrogen receptors in the endothelium suggests that this enzyme may be regulated through non-genomic, non-traditional estrogen mechanisms. By measuring the changes in activity and transcriptional expression for this enzyme after estrogen, these efforts should better characterize these important interactions between steroids and nitric oxide mechanisms.

Representative Publications:

Jarow, J.P., Kirkland, J., Koritnik, D.R., and W.T. Cefalu. "Effect of obesity and fertility status upon sex steroid levels in men." Urology 42:171-174, 1993

Bell, D.R., Rensberger, H.J., Koritnik, D.R. and A. Koshy. "Estrogen pretreatment directly potentiates endothelium-dependent vasorelaxation of porcine coronary arteries." Am J Physiol 268:H377-H383, 1995

Koritnik, D.R., Koshy, A. and R. Hoversland. 17B-Estradiol treatment increases the levels of estrogen receptor and its mRNA in male rat liver." Steroids 60:519-529, 1995

Bell, D.R., Rensberger, H.J., Koritnik, D.R. and A. Koshy. "Effects of estrogen on noradrenergic vasorelaxation of porcine coronary arteries." General Pharmacol 26:1289-1294,1995

Koritnik, D.R., and Marschke, K.B., and A. Koshy. "Characterization of a hepatic binding proteinin non-human primates which binds mibolerone but not dihydrotestosterone or methytrienolon.Steroids 60:759-767, 1995