|Klemcke, Harold - FORMER ARS EMPLOYEE|
Submitted to: Experimental Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 13, 2006
Publication Date: May 20, 2006
Citation: Klemcke, H.G., Vallet, J.L., Christenson, R.K. 2006. Lack of effect of metyrapone and exogenous cortisol on early porcine conceptus development. Experimental Physiology. 91(3):521-530. Interpretive Summary: There are 30-50% fetal losses in pigs, and when the uterus is crowded, additional losses occur between days 25 and 40 of gestation. Such occult embryonic mortality greatly reduces swine litter size, and imposes economic losses on swine producers. In order to increase swine litter size it is important to understand factors that limit litter size, and to understand those factors that are important for normal prenatal development. One such factor could be the steroid hormone cortisol. In other species optimal cortisol concentrations are beneficial to normal development, yet excessive concentrations are known to limit growth and increase mortality. The current study was conducted to evaluate the influence of maternal cortisol on early embryonic development in pigs. Use was made of a drug to block maternal cortisol production to determine if low maternal cortisol influenced early embryonic growth and survival. Then the same drug plus cortisol were administered to determine if cortisol could reverse any drug-related effects. No treatment-related effects on fetal size or survival were measured which may reflect the fact that cortisol levels were lowered, but not eliminated. Statistically significant relationships between maternal cortisol levels and specific embryonic measures (size, and fluid volume) however, do suggest that an appropriate cortisol environment may be necessary for optimal porcine embryonic development during this stage of gestation.
Technical Abstract: A study was conducted to evaluate the influence of maternal cortisol on early conceptus development in pigs (Sus scrofa). The corticosteroid synthesis inhibitor metyrapone was injected during days 14-19 of pregnancy, without (n = 6) and with (n = 6) commensurate administration of cortisol. Blood samples were taken via indwelling catheters on days 14 and 18, and conceptuses were collected during surgery on day 20. Compared with vehicle injected control pigs (n = 7) plasma cortisol and aldosterone concentrations were decreased (P < 0.01) 52.5 and 33%, respectively, by metyrapone treatment. Cortisol administration reversed decreases in plasma cortisol. There were no treatment-associated effects on conceptus survival or size. Nor were there treatment-associated effects on allantoic fluid volume or content. Trophodermal glucocorticoid receptor mRNA expression decreased 34.4% (P = 0.04) in metyrapone treated pigs, and was not further influenced by concomitant administration of cortisol. Also, when all pigs were considered there were treatment-independent 2nd order polynomial regressions (P < 0.05) between maternal plasma cortisol concentrations and embryonic weight, allantoic size, and allantoic glucose concentrations. Such biphasic cortisol-concentration vs tissue-measure curves suggest that an appropriate glucocorticoid environment may be necessary for optimal porcine embryonic development during this stage of gestation.