Reproductive endocrinology of environmental nitrate.
Gen Comp Endocrinol
; 265: 31-40, 2018 09 01.
Article
em En
| MEDLINE
| ID: mdl-29577898
ABSTRACT
Nitrate is a widespread contaminant of aquatic ecosystems and drinking water. It is also broadly active in organismal physiology, and as such, has the potential to both enhance and disrupt normal physiological function. In animals, nitrate is a proposed endocrine disrupter that is converted in vivo to nitrite and nitric oxide. Nitric oxide, in particular, is a potent cell signaling molecule that participates in diverse biological pathways and events. Here, we review in vivo nitrate cycling and downstream mechanistic physiology, with an emphasis on reproductive outcomes. However, in many cases, the research produces contradictory results, in part because there is good evidence that nitrate follows a non-monotonic dose-response curve. This conundrum highlights an array of opportunities for scientists from different fields to collaborate for a full understanding of nitrate physiology. Opposing conclusions are especially likely when in vivo/in vitro, long term/short term, high dose/low dose, or hypoxia/normoxia studies are compared. We conclude that in vivo studies are most appropriate for testing an organism's integrated endocrine response to nitrate. Based on the limited available studies, there is a generalized trend that shorter term studies (less than 1â¯month) or studies involving low doses (≤5â¯mg/L NO3-N) cause steroid hormone levels to decline. Studies that last more than a month and/or involve higher, but still environmentally relevant, exposures (>50-100â¯mg/L NO3-N) cause steroid hormone levels to increase. Very high nitrate doses (>500â¯mg/L NO3-N) are cytotoxic in many species. Hypoxia and acidity are likely to intensify the effects of nitrate. For study design, degree of study animal reproductive maturity or activity is important, with immature/reproductively quiescent animals responding to nitrate differently, compared with reproductively active animals. A detailed table of studies is presented.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Reprodução
/
Poluentes Ambientais
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Nitratos
Idioma:
En
Ano de publicação:
2018
Tipo de documento:
Article