F.R. Carman

Stability of human chorionic gonadotropin and its alpha subunit in human blood

The stability of human chorionic gonadotropin (hCG) and its alpha-subunit in whole blood, plasma, and serum under a variety of sample handling conditions commonly encountered in clinics, hospital wards, physicians offices, and clinical service laboratories was investigated with the use of radioreceptor assay, radioimmunoassays, as well as hormone integrity determinations. The results clearly demonstrate that hCG and its alpha-subunit are stable in unfrozen whole blood, plasma, and serum for at least 6 days and in frozen plasma and serum samples for at least 6 months. Repeated freezing and thawing of the samples during this period had no effect. Separation of plasma or serum from erythrocytes is not needed for at least 12 hours. Hemolysis in samples resulted in a 20% to 30% decrease in hCG and its alpha-subunit levels, which may be attributable to sample dilution.

Stimulation of ovarian cyclic guanosine 3′, 5′-monophosphate levels by the subunits of human chorionic gonadotropin

Abstract Injection of human chorionic gonadotropin (HCG) into the tail vein of superovulated rats resulted in a significant (P

Role of luteal cell nucleus in the expression of gonadotropin action

Gonadotropin receptors are not only present in cell membranes, but also in nuclei of bovine and human luteal cells. hCG/hLH can directly regulate several nuclear functions. To further investigate the role of luteal cell nucleus in the expression of gonadotropin action, the effect of enucleation of luteal cells on gonadotropin receptors and gonadotropin response was studied. Luteal cytoplasts were prepared by colchicine treatment of purified whole luteal cells followed by centrifugation at 37 C in a Percoll gradient. The cytoplasts were 85 to 90% pure with a recovery of about 57%. Cytoplasts were viable as determined by trypan blue exclusion (87%) and metabolically competent as determined by 3H-leucine incorporation into proteins. On the day of preparation, the viability and metabolic competency of cytoplasts were similar to control cells, i.e. untreated and colchicine treated whole luteal cells. In addition, cytoplasts and control cells showed a similar decline in number and viability during storage at 4 C. While control cells continue to be metabolically competent, cytoplasts showed a dramatic decline by 48 h of storage at 4 C. Neither the cytoplasts nor control cells degraded 1251-hCG. The kinetics of 1251-hCG association and dissociation, specificity and affinity of binding to cytoplasts were similar to control cells. However, the number of available gonadotropin receptors in cytoplasts was significantly lower than in control cells. Cytoplasts contained lower progesterone levels and more importantly, they could not be stimulated by 10 nM hCG or 10 mM dibutyry1 cyclic AMP to produce more progesterone. Controls cells, on the other hand, contained higher progesterone levels and responded to hCG and dibutyryl cyclic AMP stimulation. In summary, removal of nuclei from luteal cells results in a partial loss of gonadotropin receptors and complete loss of steroidogenic response to hCG and dibutyryl cyclic AMP. Whether the loss of steroidogenic response was related or coincidental to partial gonadotropin receptors loss is unknown.

The nature of reversible and not readily reversible bovine corpus luteum plasma membranes bound human chorionic gonadotropin

Abstract125I-human chorionic gonadotropin (125I-hCG) bound to plasma membranes of bovine corpora lutea consisted of reversible and not readily reversible fractions. The not readily reversible fraction progressively increased as the length and the temperature of preincubation were increased. The not readily reversible fraction was, however, completely eluted after any time or temperature of preincubation. Although the not readily reversible and reversible bound 125I-hCG were precipitated equally well with 10% trichloroacetic acid, the not readily reversible bound 125I-hCG was able to rebind much higher to fresh plasma membranes compared to reversible bound 125I-hCG. These findings suggest that while not readily reversible bound 125I-hCG was intact, the reversible bound 125I-hCG was somewhat altered during the binding reaction.

THE INTRACELLULAR ORGANELLES OF HUMAN OVARIES CONTAIN GONADOTROPIN RECEPTORS

SUMMARY The nuclei (N), plasma membranes (PM), mitochondria-lysosomes (M-L), rough endoplasmic reticulum (RER), and combined (light, medium and heavy) golgi (G) isolated from human ovaries specifically bound added 125 I-human chorionic gonadotropin ( 125 I-hCG). Marker enzyme analyses revealed that the 125 I-hCG binding observed in various subcellular organelles was intrinsic.