Changes in adenylyl cyclase activity of the human and nonhuman primate corpus luteum during the menstrual cycle and pregnancy.

Adenylyl cyclase (AC) activity in membrane particles of corpora lutea (CL) from humans and cynomolgus monkeys was examined at various stages of the menstrual cycle and pregnancy. AC activity was monitored by the conversion of [alpha-32P]ATP into [32P]cAMP under basal conditions and in the presence of several activators: NaF (10 mmol/L) plus forskolin (100 mumol/L); hCG (10 micrograms/mL); guanyl 5'-yl-imidodiphosphate [GMP-P(NH)P; 100 mumol/L]; and hCG (10 micrograms/ml) plus GMP-P(NH)P (100 mumol/L). The groups of human CL were midluteal (n = 10), late luteal (n = 4), following cycle (old CL; n = 5), and early pregnancy (6-11 weeks; n = 10). The groups of monkey CL were early luteal (n = 4), midluteal (n = 5), and pregnancy at term (n = 3). Luteal AC activity changed significantly during the menstrual cycle. In newly (less than 48 h after ovulation) formed CL, the enzyme was unresponsive to hCG, and total AC activity, as determined by NaF plus forskolin, averaged 86.5 +/- 28.9 (+/- SE) pmol cAMP/min.mg protein. As the CL developed, AC activity increased. Thus, in the midluteal phase, maximal hCG responsiveness in the presence of guanine nucleotide was 125 +/- 27 and 232 +/- 15 pmol/min.mg in human and monkey CL, respectively. No hCG responsiveness was detected in the late luteal phase or in the old CL. Maximal AC activity was also high in the midluteal phase (382 +/- 56 and 256 +/- 28 pmol/min.mg in human and monkey CL, respectively); the activity remained fairly high during the late luteal phase and then declined to less than 100 pmol/min.mg in the follicular phase of the next cycle. During early pregnancy, luteal AC was unresponsive to hCG stimulation, yet basal levels, maximal activity, and the characteristics of stimulation by nonhormonal activators were similar, if not identical, to those at the midluteal phase of the menstrual cycle. At term pregnancy, the enzyme remained unresponsive to hCG. However, basal activity and stimulation by NaF and forskolin were remarkably elevated, being between 2- and 7-fold higher than corresponding stimulations in the midluteal phase. We conclude that 1) AC activity in human luteal membranes is highly dependent on hormonal changes and functional state of the ovary, 2) the activity of luteal AC is similar in the CL of humans and cynomolgus monkeys, and 3) the AC system in the primate CL is functionally active during and at the end of pregnancy.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunoreactive insulin-like growth factor I in human follicular fluid.

Recent studies in laboratory animals suggest that insulin-like growth factor I (IGF-I) plays an important role in the regulation of granulosa cell function. The purpose of the present study was to investigate the presence of immunoreactive IGF-I in human follicular fluid (FF) and compare the levels of follicular IGF-I (64 follicles) with those detectable in serum (n = 19) in hyperstimulated cycles from 25 infertile patients. Also, the FF IGF-I levels were correlated to corresponding follicular volume (n = 62) and oocyte maturation (n = 37). Levels of IGF-I were determined using a specific radioimmunoassay after acidification and extraction by reversed phase chromatography. Levels of IGF-I in serum were significantly higher than those in FF (37.1 +/- 10.1 versus 24.0 +/- 9.3 nmol/l, n = 19, P less than 0.001). A positive correlation was found between follicular and serum IGF-I concentrations (r = 0.73). No significant differences were found in FF IGF-I levels derived from follicles of different size or from follicles having oocytes with different grades of maturation. These data indicate that immunoreactive IGF-I is present in human FF in nanomolar concentrations and that FF IGF-I levels correlate with those detectable in serum. The source of FF IGF-I and its regulatory role in humans remains to be elucidated.

P-glycoprotein expression in human breast cancer cells.

Multidrug resistance in Chinese hamster ovary cells is associated with the Mr 170,000 surface glycoprotein. Using our monoclonal antibody to this protein, we have isolated a complementary DNA clone from an expression vector library. This complementary DNA recognizes a 4.5-kilobase mRNA in drug-resistant but not-sensitive Chinese hamster ovary cells; it also recognizes a 5.0-kilobase mRNA in our Adriamycin-resistant subline of the MDA-231 human breast cancer cell line which is not expressed in the drug-sensitive parent line. Southern blot analysis shows that the P-glycoprotein sequences are greatly amplified in resistant Chinese hamster ovary cells but not in the resistant human breast cancer cells, indicating that amplification and expression of the Mr 170,000 P-glycoprotein gene are not necessarily coordinate events. Amplification of this gene may not be required for multidrug resistance in human cells.