Physiological Regulation of Luteinizing Hormone(LH) Expression in Rat Mammary Gland during Differentiation = 분화중인 흰쥐 유선내 Luteinizing Hormone (LH) 유전자 발현의 생리적인 조절

국문 초록 (Abstract)

태반이나 생식소 등 시상하부 이외의 조직에서도 gonadotropin releasing hormone(GnRH)과 그 수용체가 발현되어 조직 특이적인 기능을 담당함은 잘 알려진 사실이다. 최근 GnRH와 그 수용체 유전자가 흰쥐 유선에서도 발현됨이 증명되었고, LH -와 -subunit와 LH 수용체에 대한 전사체 역시 흰쥐 유선에 존재함이 확인되었다 본 연구는 흰쥐 유선 LH의 발현과 유선의 분화과정 간의 상관관계를 조사하기 위해서 생식주기, 임신

다국어 초록 (Multilingual Abstract)

The ectopic expression of gonadotropin releasing hormone(GnRH and luteinizing hormone(LH) in several tissues is a quite intriguing phenomenon. Recently, the presence of GnRH and its receptor has been clearly demonstrated in rodents and human mammary gland. In this context, one can postulate that the presence of local circuit composed of GnRH and LH in the gland. The present study was undertaken to elucidate whether there is a correlation between the LH expression in rat mammary gland and physiological status during the process of mammary differentiation. LH contents in mammary gland from cycling to weaning rats were measured by radioimmunoassay(RIA). In cycling rats, changes of the LH level in both serum and mammary gland showed similar pattern as the highest level in proestrus and the lowest level in diestrus II stage. While the serum LH levels were fluctuated from pregnant through involution stage, a sharp decline of mammary LH contents was observed in the lactating rats. This decrement was recovered in involuting rats to the level of proestrus stage. Reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot analyses demonstrated that the transcriptional activities of the mammary LH and GnRH were increased from diestrus I stage to estrus stage, and the increased levels were maintained in pregnant, lactation and involution stages. To test the hypothesis that the alteration in mammary LH expression might be steroid-dependant, ovariectomy(OVX) and steroid supplement model was employed. As expected, supplement of estradiol(E) after OVX remarkably decreased serum LH level compared to that in serum from vehicle-only treated rats. Likewise, administration of E significantly reduced the mammary LH content. The present study demonstrated that (i) the LH expression in mammary gland could be altered by some physiological parameters such as estrous cycle, pregnancy, lactation and involution, and (ii) ovarian steroid especially estrogen seems to be one of major endocrine factors which are responsible for regulation of mammary LH expression.