Plasma Luteinizing Hormone and Oestrogen in Foetal and Maternal Sheep

Abstract

Welsh mountain sheep of known conceptual age (term 148 days) were given a spinal anaesthetic (2 ml 20% procaine). A hind leg artery was catheterized, the foetus was exposed by Caesarian section, allantoic and amniotic fluids were collected and a catheter inserted into a tributary of an umbilical artery. Blood samples were taken within 15 min of anaesthesia. The heparinized plasma was separated immediately in the cold and stored at \m=-\15 \ s=deg\ C. Luteinizing hormone (LH) and 17\g=b\-oestradiol were determined by radioimmunoassay (Naftolin & Corker, 1971) and competitive binding assay (Corker & Exley, 1970). The oestradiol method removes oestrone and oestriol, but 17\g=a\-oestradiolwould interfere if present in quantities approaching those of 17\g=b\-oestradiol.No, or just detectable, LH activity was found in plasma from mothers or from older foetuses (Table 1). Measurable LH was present in the plasma of 10 out of 11 foetuses aged 117 days or less. There was a wide range in levels. In two animals (484/70 and 477/70) two consecutive samples gave similar values. However a sample taken from animal 477/70 after a large haemorrhage gave a much lower value. Oestradiol was not measurable in either foetal or maternal plasma from early gesta¬ tions (Table 1), but significant quantities were present in some of the older animals from 130 days onward. Particularly high values were found in animals 500/70 (near term) and C/70. The latter may have also been near term; the estimate of its age was based upon weight and length only. No LH was found in any of the foetal fluids except for traces ( < 0-5 ng/ml) in 487/70 and 485/70 (amniotic fluid) and 485/70 and 490/70 (allantoic fluid). Traces of oestrogens were found in three of six amniotic and five of seven allantoic fluids (0-3-2 ng/100 ml).The low levels of LH in maternal plasma late in pregnancy resembled those seen in dioestrous ewes (Bjersing, Hay, Kann, Moor, Naftolin, Scaramuzzi, Short & YoungLai, 1972). The presence of LH, particularly in the plasma of younger foetuses, has also been reported by Foster, Roach, Karsh, Norton, Cook & Nalbandov (1972) with post-mortem material. The fall in LH occurred when measurable levels of 17/?-oestradiol first appeared. Thus 17/?-oestradiol may suppress LH secretion. Since LH was present in foetal but not maternal blood it must be of foetal origin and the J Present address:

Evidence that the corpus luteum of pregnancy contributes to the control of tonic secretion of LH in the ewe

“…after Day 50) were maintained at low levels with an overall mean of 0-3 ng/ml. This finding is in agreement with a previous study (Alexander et al, 1973) in which only one blood sample was collected at each stage of pregnancy.…”

The Concentrations of Androgens, Oestrogens, Progesterone and Luteinizing Hormone in the Serum of Foetal Calves Throughout the Course of Gestation

“…However, in the 9th month of pregnancy, LH remained low while oestradiol increased. Similar results have been obtained in foetal lambs (Alexander et al 1973) and although serum LH is low during late pregnancy, the concentration of LH in the pituitary of lambs (Foster et al 1972) and calves (Desjardins & Hafs, 1968) at birth is high.…”

“…The female or neutral pattern of development is modified in males by androgen secreted from the testes (Jost, 1969(Jost, , 1970, and, in addition, sexual differentiation of the brain is controlled by steroid hormones (Gorski, 1971). Changes in steroid levels may also influence the secretion of gonadotrophins by the foetal pituitary gland (Foster, Roach, Karsch, Norton, Cook & Nalbandov, 1972;Alexander, Britton, Corker, Naftolin & Nixon, 1973). Finally it has been established that the interaction between the foetal pituitary and adrenal glands is pronounced during the later stages of pregnancy (Bassett & Thorburn, 1969), and has been implicated in the initiation of parturition (Liggins, 1969).…”

Expression of estrogen receptors in the efferent ductule of male sheep fetuses during gestation

“…These results demonstrate that both ERa-immunoreactive intensity and ERa-immunopositive cell number are higher at about the middle stage of gestation than at early and late stages of gestation. In addition, the above changing pattern of ERa expression is parallel to the change of plasma estrogen concentrations during gestation (Alexander et al 1973); these suggest that estrogen has roles in the development and functions of the efferent ductules by combining with ERa. In support of this, the ERa knockout mouse shows developmental anomalies and dysfunctions of efferent ductules, and ER blockage with ICI 182,780 results in morphological changes of mouse efferent ductules (Lee et al 2000).…”