Dopamine in hypophysial portal plasma of the rat during the estrous cycle and throughout pregnancy.
Dopamine in hypophysial portal plasma of the rat during the estrous cycle and throughout pregnancy.
复制标题
动情周期和整个妊娠期间大鼠垂体门静脉血浆中的多巴胺。
作者：
N. Ben;Ch. Oliver;Howard J. Weiner;R. S. Mical;John C. Porter
在妊娠和非妊娠雌性大鼠以及完整和去势雄性大鼠中，使用放射酶测定法同时测定50穆尔血浆中的多巴胺、去甲肾上腺素和肾上腺素，测定垂体门静脉血浆中的儿茶酚胺水平。从麻醉大鼠以7穆尔/min采集门静脉血和动脉血60 min。在采集过程中，血液保持在0 ℃，在该温度下内源性儿茶酚胺相对稳定。多巴胺在垂体门脉血浆中的浓度很高，在妊娠第20天达到接近20 ng/ml。同一大鼠动脉血浆中的多巴胺水平较低或检测不到（0.4- 0.8 ng/ml）。在这些大鼠的门静脉和动脉血浆中未检测到去甲肾上腺素和肾上腺素（小于0.6 ng/ml）。孕鼠下丘脑提取物中的主要儿茶酚胺是去甲肾上腺素，而垂体后叶中的主要儿茶酚胺是多巴胺。在发情前期、发情期、发情间期1和发情间期2期间采集的门静脉血浆中多巴胺水平分别为1.32 +/- 0.21（平均值+/- SE）、3.87 +/- 0.96、3.11 +/- 0.73和2.3 +/- 0.45。完整和去势雄性大鼠门静脉血浆中的多巴胺约为0.6 ng/ml。在这些动物的门静脉或动脉血浆中均未检测到去甲肾上腺素和肾上腺素。结论是：1）多巴胺在妊娠期间大量分泌到垂体门静脉血中，2）周期性大鼠下丘脑多巴胺分泌在发情和间情早期以及至少在发情前期最大，3）这些发现支持下丘脑起源的多巴胺可能在垂体前叶功能调节中起重要作用的观点。
Catecholamine levels in hypophysial portal plasma were determined in pregnant and non-pregnant female rats as well as in intact and castrated male rats, using a radioenzymatic assay for the simultaneous determination of dopamine, norepinephrine, and epinephrine in 50 mul of plasma. Portal and arterial blood were collected from anesthetized rats at 7 mul/min for 60 min. During the collection, blood was kept at 0 C, a temperature at which endogenous catecholamines were relatively stable. Dopamine was present in high concentrations in hypophysial portal plasma thorughout pregnancy, attaining a level near 20 ng/ml on the 20th day of gestation. Dopamine levels in arterial plasma from the same rats were low or undetectable (0.4--0.8 ng/ml1. Norepinephrine and epinephrine was undetectable (less than 0.6 ng/ml) in portal as well as arterial plasma from these rats. The major catecholamine in extracts of the hypothalamus from pregnant rats was norepinephrine, whereas that in the posterior pituitary was dopamine. Dopamine levels in portal plasma collected during proestrus, estrus, diestrus 1, and diestrus 2, were 1.32 +/- 0.21 (mean +/- SE), 3.87 +/- 0.96, 3.11 +/- 0.73, and 2.3 +/- 0.45, respectively. Dopamine in portal plasma from intact and from castrated male rats was approximately 0.6 ng/ml. Norepinephrine and epinephrine were not detectable in either portal or arterial plasma from these animals. It is concluded 1) that dopamine is secreted into hypophysial portal blood in significant quantities during pregnancy, 2) that hypothalamic secretion of dopamine in cyclic rats is greatest during the day of estrus and early diestrus and at least on the day of proestrus, and 3) that these findings support the view that dopamine of hypothalamic origin may have an important role in the regulation of anterior pituitary function.