Norepinephrine in the Rat Ovary: Ontogeny andde NovoSynthesis*

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Abstract
The ontogeny of catecholamines (CA) in the rat ovary, the ability of the immature ovary to synthetize norepinephrine (NE) in vitro, and the correlation between ovarian CA and plasma pituitary hormones were studied. Ovaries, spleen (as a control tissue not subjected to endocrine regulation), and trunk blood were collected at 5-day intervals between days 5 and 40. Ovarian NE concentration increased markedly between days 20 and 35 of life, whereas the major rise in splenic NE concentration occurred between days 10 and 15. Ovarian and splenic tissues from neonatal females were capable of de novo synthesis of NE from tritiated tyrosine without an appreciable accumulation of L-dopa and dopamine. The rate of NE synthesis by ovarian tissue taken from 20-day-old rats was significantly lower than that from 30- and 40-day-old rats, whereas NE productions by splenic tissue from 20-, 30-, and 40-day-old rats were similar. Plasma FSH concentration was significantly elevated between days 10 and 20, whereas the major rise in plasma LH [luteinizing hormone] and PRL [prolaction] occurred between days 25 and 40. The delayed elevation of ovarian NE, compared to splenic NE, is attributable to a decreased production of NE by the ovary on day 20 and may involve of a key CA biosynthetic enzyme such as tyrosine hydroxylase. Given the temporal relationship between plasma gonadotropins, in particular FSH, and changes in ovarian NE, ovarian CA during neonatal development may be subjected to regulation by circulating pituitary hormones.