Studies on Human Sexual Development IV. Fetal Pituitary and Serum, and Amniotic Fluid Concentrations of Prolactin J. A. CLEMENTS, F. I. REYES, J. S. D. WINTER,1 AND C. FAIMAN Departments of Physiology, Obstetrics and Gynaecology and Paediatrics, University of Manitoba, and the Endocrine and Metabolic Sections of the Health Sciences Centre, Winnipeg, Manitoba, Canada ABSTRACT. Prolactin concentrations were measured in 161 amniotic fluid specimens from 8-40 weeks fetal age and the levels compared with those observed in 45 fetal and neonatal cord sera and in 42 fetal pituitary specimens. Amniotic fluid prolactin levels rose steeply between 12-16 weeks gestation, and then declined to term; the calculated total amniotic fluid content of prolactin showed a similar pattern, but the peak was later, at about 26 weeks gestation. Amniotic fluid concentrations consistently exceeded fetal serum prolactin levels, even dur-
ing the last trimester, when fetal serum and pituitary levels were highest. The data are compatible with a fetal origin for amniotic fluid prolactin, but only if one assumes that flux of prolactin out of amniotic fluid compartment is negligible, that the fetal kidney in mid-pregnancy clears prolactin at a rate virtually equal to the glomerular filtration rate, and the fetal pituitary shows secretion characteristics quite different from those of the adult gland. (J Clin Endocrinol Metab 44: 408, 1977)
P
ROLACTIN in large amounts which is immunologically (1,2) and chromatographically (1-3) similar to that of pituitary origin is present in the amniotic fluid of primates, especially during the second trimester of pregnancy (1,2,4-9). Several functions for prolactin during pregnancy have been suggested, including influences upon salt and water homeostasis in amniotic fluid and the fetus (1,10), control of fetal adrenal growth (11) and suppression of testicular testosterone secretion in the latter half of gestation (12), but these remain speculative. The origin of prolactin in amniotic fluid remains unclear. Conflicting evidence exists in favor of a fetal (2,7), maternal (5,9), or placental (1,8) source. In an attempt to assess the likelihood of a fetal origin we have studied human fetal serum and pituitary concentrations of prolactin in relation to amniotic fluid concentration.
Materials and Methods Abortus specimens, ranging in fertilization age from 8-20 weeks2 were obtained immediately after hysterotomy performed for gynecosocial indications Received June 16, 1976. Reprint requests to: Dr. C. Faiman, Health Sciences Centre, 700 William Avenue, Winnipeg, Manitoba, Canada R3E 0Z3. Supported in part by: Medical Research Council of Canada Grant MT-2997. 1 Queen Elizabeth II Scientist. 2 Fetal age was estimated either by conversion from crown-rump length data according to Patten (13) or by
on otherwise healthy pregnant women. Sex was determined by karyotype and gonadal histology in the smaller fetuses, and by examination of internal and external genitalia in those over 5 cm crown-rump (CR) length (14). Fetal blood was obtained by cardiac puncture and the serum frozen (-20 C) until analyzed. Fetal pituitary glands were excised without delay, weighed and frozen (-20 C) until analyzed. At the time of assay, the glands were homogenized in 2-4.5 ml cold (4C) 0.07M, pH 8.6, sodium barbital; the homogenate was centrifuged at 3000 rpm for 15 min at 4 C, and the supernatant collected for radioimmunoassay. Amniotic fluid specimens over the fetal age range 8-20 weeks were obtained at the time of hysterotomy or by transabdominal amniocentesis prior to administration of hypertonic saline for therapeutic abortion. Another series of amniotic fluids, ranging from 23-40 weeks fetal age, was obtained during diagnostic aminiocentesis; in this series, only samples from pregnancies in which the entire gestation was normal and in which healthy infants were later delivered were included. Amniotic fluids were frozen (-20 C) until analyzed. Mixed arterial and venous cord serum samples were collected at delivery of full term infants and frozen (-20 C) until analyzed. Prolactin levels were measured by double-antibody radioimmunoassay according to the method of Hwang et al. (15), using rabbit anti-human prolactin (65-7), human prolactin standard (75.7.28) and prolactin-125I kindly provided by Dr. H. Friesen. Dose-response slopes of varying volumes of fetal serum, amniotic fluid and pituitary homogenates were parallel to that of the assay standard. subtracting 2 weeks from calculations based upon last normal menstrual period in cases in which fetal specimens were not obtained.
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COMMENTS Differences between groups were estimated by the Wilcoxon-Mann-Whitney Test (16). Correlation and partial correlation coefficient calculations were performed according to Snedecor (16). Samples containing amounts of hormone below the limit of assay detectability were assigned the smallest value measurable with the assay for die purpose of statistical analysis.
400 • MALE o FEMALE 300
|^ 200
Results In all of the data to follow, there was no significant difference in fetal age distribution between the sexes.
100 20
Amniotic fluid A total of 161 amniotic fluid specimens were assessed over 8-40 weeks fetal age (Fig. 1). Prior to 10 weeks fetal age (5.2 cm CR length), prolactin levels averaged 4.2 ng/ml (range 2.56.5). There was a sharp increase in both sexes to reach a peak mean value of 1314 ng/ml (range
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FlG. 2. Prolactin concentrations in fetal serum as a function of age, crown rump length and sex, and in newborn mixed cord serum.
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ing the last trimester, when fetal serum and pituitary levels were highest. The data are compatible with a fetal origin for amniotic fluid prolactin, but only if one assumes that flux of prolactin out of amniotic fluid compartment is negligible, that the fetal kidney in mid-pregnancy clears prolactin at a rate virtually equal to the glomerular filtration rate, and the fetal pituitary shows secretion characteristics quite different from those of the adult gland. (J Clin Endocrinol Metab 44: 408, 1977)
P
ROLACTIN in large amounts which is immunologically (1,2) and chromatographically (1-3) similar to that of pituitary origin is present in the amniotic fluid of primates, especially during the second trimester of pregnancy (1,2,4-9). Several functions for prolactin during pregnancy have been suggested, including influences upon salt and water homeostasis in amniotic fluid and the fetus (1,10), control of fetal adrenal growth (11) and suppression of testicular testosterone secretion in the latter half of gestation (12), but these remain speculative. The origin of prolactin in amniotic fluid remains unclear. Conflicting evidence exists in favor of a fetal (2,7), maternal (5,9), or placental (1,8) source. In an attempt to assess the likelihood of a fetal origin we have studied human fetal serum and pituitary concentrations of prolactin in relation to amniotic fluid concentration.
Materials and Methods Abortus specimens, ranging in fertilization age from 8-20 weeks2 were obtained immediately after hysterotomy performed for gynecosocial indications Received June 16, 1976. Reprint requests to: Dr. C. Faiman, Health Sciences Centre, 700 William Avenue, Winnipeg, Manitoba, Canada R3E 0Z3. Supported in part by: Medical Research Council of Canada Grant MT-2997. 1 Queen Elizabeth II Scientist. 2 Fetal age was estimated either by conversion from crown-rump length data according to Patten (13) or by
on otherwise healthy pregnant women. Sex was determined by karyotype and gonadal histology in the smaller fetuses, and by examination of internal and external genitalia in those over 5 cm crown-rump (CR) length (14). Fetal blood was obtained by cardiac puncture and the serum frozen (-20 C) until analyzed. Fetal pituitary glands were excised without delay, weighed and frozen (-20 C) until analyzed. At the time of assay, the glands were homogenized in 2-4.5 ml cold (4C) 0.07M, pH 8.6, sodium barbital; the homogenate was centrifuged at 3000 rpm for 15 min at 4 C, and the supernatant collected for radioimmunoassay. Amniotic fluid specimens over the fetal age range 8-20 weeks were obtained at the time of hysterotomy or by transabdominal amniocentesis prior to administration of hypertonic saline for therapeutic abortion. Another series of amniotic fluids, ranging from 23-40 weeks fetal age, was obtained during diagnostic aminiocentesis; in this series, only samples from pregnancies in which the entire gestation was normal and in which healthy infants were later delivered were included. Amniotic fluids were frozen (-20 C) until analyzed. Mixed arterial and venous cord serum samples were collected at delivery of full term infants and frozen (-20 C) until analyzed. Prolactin levels were measured by double-antibody radioimmunoassay according to the method of Hwang et al. (15), using rabbit anti-human prolactin (65-7), human prolactin standard (75.7.28) and prolactin-125I kindly provided by Dr. H. Friesen. Dose-response slopes of varying volumes of fetal serum, amniotic fluid and pituitary homogenates were parallel to that of the assay standard. subtracting 2 weeks from calculations based upon last normal menstrual period in cases in which fetal specimens were not obtained.
408
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 26 October 2015. at 20:02 For personal use only. No other uses without permission. . All rights reserved.
409
COMMENTS Differences between groups were estimated by the Wilcoxon-Mann-Whitney Test (16). Correlation and partial correlation coefficient calculations were performed according to Snedecor (16). Samples containing amounts of hormone below the limit of assay detectability were assigned the smallest value measurable with the assay for die purpose of statistical analysis.
400 • MALE o FEMALE 300
|^ 200
Results In all of the data to follow, there was no significant difference in fetal age distribution between the sexes.
100 20
Amniotic fluid A total of 161 amniotic fluid specimens were assessed over 8-40 weeks fetal age (Fig. 1). Prior to 10 weeks fetal age (5.2 cm CR length), prolactin levels averaged 4.2 ng/ml (range 2.56.5). There was a sharp increase in both sexes to reach a peak mean value of 1314 ng/ml (range
10
0
L
8
12
16
20
CORD
FETAL AGE (weeks) i
3000
o
3
•
i """™""""~~~™T~~
8
14
i
18.5
CROWN RUMP LENGTH (cm) •
o
•
• MALE oFEMALE
o
FlG. 2. Prolactin concentrations in fetal serum as a function of age, crown rump length and sex, and in newborn mixed cord serum.
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