Regulation of Growth and Function of Lifeline Placenta.

Placenta is an association of fetal and maternal tissues which develops during pregnancy. Placenta is often called lifeline, because it is the link between mother and growing fetus. It serves variety of functions, which include transport of nutrients to growing fetus, waste products from fetus, exchange of gases and also immunological protection to the fetus. It has a unique ability to function as a hypothalamo-pituitary-gonadal-axis as it can produce a variety of peptide, protein and steroid hormones. Thus, it is an autonomous unit capable of regulating its own growth and function.

Gonadotropin releasing hormone in first trimester human placenta: Isolation, partial characterisation and in vitro biosynthesis.

Using a specific radioimmunoassay for gonadotropin releasing hormone, the presence of gonadotropin releasing hormone like material in the first trimester human placenta has been demonstrated. The material has been partially characterized using carboxy methyl cellulose chromatography, high pressure gel permeation chromatography and reverse phase C18 high pressure liquid chromatographic analysis. Analysis for bioactivity revealed that placental gonadotropin releasing hormone is much more active than synthetic gonadotropin releasing hormone in in vitro rat pituitary lutinising hormone release assay. In vitro biosynthetic studies using labelled precursors and immunoaffinity chromatography indicated that first trimester human placenta synthesizes gonadotropin releasing hormone like material.

Plasma levels of gonadotropin releasing hormone during menstrual cycle of Macaca radiata.

Α sensitive radioimmunoassay for gonadotropin releasing hormone has been developed. The assay has been validated for its specificity by testing various analogues of gonadotropin releasing hormone. Analysis of plasma samples during the menstrual cycle of 4 female bonnet monkeys showed a significant increase in the immunoreactive gonadotropin releasing hormone levels during preovulatory period of the menstrual cycle.

A solid phase radioimmunoassay for detection of early pregnancy in the South Indian bonnet monkey Macaca radiata.

Using an antibody raised in the rabbit to ovine leutenizing hormone β subunit coupled to activated cellulose, a solid phase radioimmunoassay to detect early pregnancy in the South Indian bonnet monkey has been developed. Non-specific inhibition due to serum was eliminated by inclusion of new born calf serum in the assay tubes. The assay is simple, needs only one centrifugation and can be completed in 6 h at room temperature with no false positive results.

Studies on regulation of chorionic gonadotropin secretion in primates.

The regulation of secretion of chorionic gonadotropin in primates has been studied using both in vivo and in vitro models. In vivo studies using the pregnant bonnet monkey revealed that at the doses tested, the administration of progesterone or estradiol 17β in combination or alone did not result in any appreciable change in the duration or magnitude of serum chorionic gonadotropin levels. However, administration of lutropin-releasing hormone by intravenous route resulted in significant increase in chorionic gonadotropin levels within 30–60 min and the extent of stimulation seemed to depend on the state of pregnancy. For in vitro studies, explants or cells prepared from first trimester human placenta has been used. The functional integrity of these cells has been established by demonstrating the binding of [125I]- labelled human chorionic gonadotropin antibody to the cells as well as the synthesis of [3H]- labelled human chorionic gonadotropin. In vitro studies using the cells revealed that addition of lutropin-releasing hormone caused a significant increase in chorionic gonadotropin and estradiol 17 β secreted into the medium. Thus both in vivo and in vitro results suggest that lutropin-releasing hormone could be one of the factors involved in regulation of chorionic gonadotropin secretion in primates.

Effect of human chorionic gonadotropin on serum levels of progesterone and estrogens in the pregnant bonnet monkev (Macaca radiata).

Administration of human chorionic gonadotropin to pregnant bonnet monkeys (Macaca radiata) at 55-60 days and 130-140 days of pregnancy resulted in a significant increase in serum progesterone levels. This effect could be observed even in lutectomized monkeys. However, no significant change in the serum estrogen level was noticed. These results suggest that although no chorionic gonadotropin is detectable in the serum after 35 days of pregnancy, the foetoplacental steroidogenic system is still responsive to exogenous gonadotropic stimulation.

The role of follitropin and lutropin on the ovarian function in rats.

Adult cycling female rats were treated with antisera to highly purified human follitropin and lutropin for eight days. The effect of this treatment on the in vitro steroidogenic response of the ovarian cells isolated from these rats to follitropin and lutropin has been investigated. Neutralisation of follitropin did not have significant effect on steroid production in response to lutropin. However, neutralisation of lutropin resulted in a very significant inhibition of response to both follitropin and lutropin.