Luteinizing Hormone Receptors in Human Ovarian Follicles and Corpora Lutea during Menstrual Cycle and Pregnancy*

Abstract

Specific high affinity, low capacity binding of [ l25 I]iodo-hCG was demonstrated in homogenates of isolated granulosa cells and corpora lutea of human ovary throughout the menstrual cycle and pregnancy. The binding of radiolabeled hCG to the receptor was time, temperature, ion concentration, and pH dependent. The treatment of ovarian membrane particles with trypsin decreased binding by about 75%, whereas treatment and neuraminidase resulted in a 400% increase in binding. These results suggest a protein nature of the receptor and that a portion of the receptors may be masked in the membrane by sialic acid. The receptor displayed high specificity for hCG and human LH, indicating that they share the same receptor site in the human ovary. The receptor bound hCG with high affinity. The apparent equilibrium association constant for hCG was 2.2 X 10 9 M~\ The receptor concentration increased from the early follicular phase to ovulation by about 1.6-fold. After an apparent transient fall associated with the ovulatory period, the receptor concentration increased further by about 4-fold by day 17 of the cycle and thereafter remained virutally unchanged until the end of the cycle. Homogenates of corpora lutea obtained during the follicuar phase aso bound specifically radiolabeled hCG, suggesting that the regression of the corpora lutea is not primarily due to the loss of receptors for human LH. The receptor concentration measured in corpora lutea of early pregnancy was clearly lower than that in corpora lutea of the menstrual cycle. This is most likely due to occupation and downregulation of the receptors by high serum hCG. The number of receptors in corpora lutea tended to increase towards the end of pregnancy.Our results indicate that the maturation and subsequent luteinization of human ovarian follicles is associated with a biphasis increase in the number of LH (hCG) receptors in granulosa cells. The changes in the concentration of available receptor may have a determining role in the regulation of follicular and corpus luteum development and function. (J Clin Endocrinol Metab 108: 307, 1981) H UMAN LH (hLH) and hCG appear to be the major luteotropic factors for the human corpus luteum during the menstrual cycle and pregnancy (1-4). Specific stimulation of steroidogenesis in human corpora lutea by hLH and hCG has been demonstrated in vitro (1, 2, 5). In addition, the administration of hCG in vivo during the early luteal phase prolongs the lifespan and function of the corpus luteum to a certain extent, but not beyond 9 days (3, 4). Other data have shown that hLH can also extend the lifespan of the corpus luteum of the menstrual cycle and increase the serum progesterone concentration (3, 4). Fundamental to our understanding of regulation of follicular development and corpus luteum function is knowledge of the properties of the gonadotropin recep-

Ovarian membrane receptors for LH, FSH and prolactin during the menstrual cycle and in polycystic ovary syndrome.

“…In the present study the LII receptor in the ML phase was 287% of that in the LF phase, which was compatible with other investigators (Wardlaw et al 1975;Rajaniemi et al 1981). In the PCO group, the binding sites for LH increased to 225% of those in the LF phase, close to those in the ML phase.…”

“…The LH receptor in human ovary increases in accordance with follicular maturation, then drops transiently at postovulatory days and again rises, finally coming up to the highest level in the luteal phase (Wardlaw et al 1975 ;Rajaniemi et al 1981). In the present study the LII receptor in the ML phase was 287% of that in the LF phase, which was compatible with other investigators (Wardlaw et al 1975;Rajaniemi et al 1981).…”

Increase of Progesterone Production in Human and Rat Luteal Cells by Beta-Adrenergic Stimulation

“…The basal secretion of luteal cells is highest in the early luteal phase in accordance with former data [19]. During the lifespan of the human corpus luteum the number of LH receptors remains constant [20], Consequently the different responses to adrenergic stimuli in different phases of cor pus luteum cannot be explained by the changes in the number and affinity of LH/hCG receptors.…”

Gonadotrophin Dependence of Steroidogenesis by Human Corpora lutea of Different Ages during the Menstrual Cycle

“…The human corpus luteum is LH-dependent, but continued administration of LH does not prolong its activity [2], The admin istration of HCG also prolongs the life span of the corpus luteum to a certain extent, but not beyond 9 days [ 13], It is widely accepted that LH and HCG exert the luteotrophic effect on human corpus luteum through the specific receptors [14][15][16][17], We have reported that the number of binding sites for both hormones increases from early to mid-luteal phase and decreases towards late luteal phase [18,19], It is suggested that the ability of luteal cells to respond to LH/HCG varies during the life span of the human corpus luteum.…”